Printable Version of Topic

Click here to view this topic in its original format

Unmanned Spaceflight.com _ Opportunity _ The Storm

Posted by: OWW Jul 5 2007, 05:57 PM

Oh no...This is getting bad:

The new and potentially bleak outlook is a stark shift from the prognosis earlier this week.

The dusty squall has reduced direct sunlight to Mars' surface by nearly 99 percent, an unprecedented threat for the solar-powered robotic explorers. If the storm keeps up and thickens with even more dust, officials fear the rovers' batteries may empty and silence the robotic explorers forever.

Opportunity's energy-gathering ability has been slashed to a dangerous 280 watt-hours-enough power to light only three 90-watt light bulbs.

"The worst-case scenario is that enough dust in the sky decreases solar energy to the point that we have to shut down too many things to save power," Lemmon said. "The rovers keep their battery alive by keeping their electronics alive."


"The reality of the situation is that we're limited as to what we can do from the ground by cutting power use," Callas said. "If it continues to worsen and stay that way, it's a survivability issue for Opportunity. If Mars wants to kill the rovers, it can."

http://www.space.com/news/070705_dusty_rovers.html

Posted by: kungpostyle Jul 5 2007, 06:32 PM

This is starting to look like it might need it's own topic.

http://www.space.com/news/070705_dusty_rovers.html

With Home plate and the inside of Victoria on the menu I really hope this blows over.

Posted by: helvick Jul 5 2007, 06:49 PM

99% drop in direct beam flux is Tau of around 5.2. That's slightly worse than the highest Tau levels measured by the Vikings in 1977.

Edited. Doh! My bad - it's actually about 4.6 which is not quite as bad as the worst the Viking's saw in 1977.

Posted by: Bobby Jul 5 2007, 06:59 PM

I saw this article on Yahoo News and thought everyone might want to see it regarding both Rovers on Mars.

Martian dust storm affecting twin rovers:

http://news.yahoo.com/s/ap/20070705/ap_on_sc/mars_rovers;_ylt=AkehfcA59RNkZbvYqwxIae_737YB

Posted by: Stu Jul 5 2007, 08:11 PM

Hope this doesn't get any worse... don't want to see pics like this coming down... sad.gif


Posted by: mchan Jul 5 2007, 08:26 PM

It would be awesome if the pictures can show something visually dramatic like that. Unfortunately, the pictures appear to show the the landscape getting slowly murkier and murkier. An animated movie would be awesome.

It's probably not too bad if any pictures can still come down. It's bad if no pictures can come down. sad.gif

Posted by: Stu Jul 5 2007, 08:31 PM

I know there's no way we'd ever get pics like that, I was just imaginin' ...

Posted by: Oren Iishi Jul 5 2007, 08:46 PM

Can the rover be shut down until the storm passes? Or at least put in sleep mode?

Posted by: MarsIsImportant Jul 5 2007, 09:04 PM

Yes, but the heaters need to be on to keep the electronics in safe condition. Nomatter what, Opportunity needs a certain level of power to survive. The latest news suggests that those power levels are uncomfortably close to that lower limit even with sleep mode.

This is a very unfortunate turn of events. But if opportunity survives intact, then this storm and its aftermath is an incredible new science opportunity for the rover. Let's just hope that the dust storm does Not get any worse than it has over the 4th of July.

If you believe in the Gia hypothesis, then maybe Mars was just celebrating with it own brand of fireworks! ;-) rolleyes.gif smile.gif ...the kind that some western states had to ban because of the drought.

Posted by: Tom Tamlyn Jul 5 2007, 09:32 PM

What is the impact of the storm on dust deposition rates? Is the activity mostly too high in the atmosphere to blow heaps of dust onto the solar arrays?

TTT

Posted by: djellison Jul 5 2007, 09:37 PM

Strangely, if I get this right - regional dust storms are quite good because they cause high wind speeds ( note the cleaning that Opportunity got just over a week ago ) - BUT I would imagine that there comes a point when the dust loading, whatever the wind speed, must cause increased deposition.

Doug

Posted by: ngunn Jul 5 2007, 09:51 PM

It must all fall down when the wind stops. If it causes almost complete obscuration when it's airborne then I fear it will do the same when it settles, unfortunately.

Posted by: djellison Jul 5 2007, 09:56 PM

What happened after the, admitedly much more modest regional storm, that Opportunity had in the 600-ish range - the one that made it sleep in late one morning?

Doug

Posted by: Sunspot Jul 5 2007, 10:06 PM

Are there any pictures of the dust storm anywhere? This isn't looking good. sad.gif

Posted by: Pavel Jul 5 2007, 10:34 PM

Would not the air be warmer if the airborne dust is consuming the solar light? It's summer in the southern hemisphere, and Mars should be close to its perihelion, so maybe the power requirements for the heater are not so high as in the middle on the winter?

Posted by: djellison Jul 5 2007, 10:39 PM

That's true - I remember the depths of Spirits winter, and they mentioned that they got away with less than the 240whrs they thought they needed, because the vehicle ended up staying warmer than they expected.

Doug

Posted by: ustrax Jul 5 2007, 10:53 PM

it is my oppinion that if Oppy survives this we should take to Ithaca...in shoulders!

Posted by: slinted Jul 5 2007, 11:05 PM

QUOTE (Sunspot @ Jul 5 2007, 03:06 PM) *
Are there any pictures of the dust storm anywhere? This isn't looking good. sad.gif


I'm sure there are other resources for finding amateur images of Mars, but the http://tech.groups.yahoo.com/group/marsobservers/ isn't a bad place to keep track of daily images of the storm. Imaging Mars isn't too easy now , but I'm consistently impressed with what you can see even in low res images. Unfortunately, you need to join the group to read the messages/see the images.

Posted by: Tom Tamlyn Jul 5 2007, 11:17 PM

Is the MRO's Mars Climate Sounder able to return observations that are helpful in understanding the current dust storms? Are the observations useful for rover operations or only for long-term assessments of the atmosphere?

TTT

Posted by: helvick Jul 5 2007, 11:49 PM

QUOTE (djellison @ Jul 5 2007, 10:56 PM) *
What happened after the, admitedly much more modest regional storm, that Opportunity had in the 600-ish range - the one that made it sleep in late one morning?
Doug

The purple line is a 30 Sol moving average and the red line is a 50 sol moving average trend line on that. I had to do that in order to dampen out the noise sufficiently to see any trends at all but it means that the data in those lines is shifted to the right by 30 and 80 sols so keep that in mind.
It is pretty clear (to me maybe others differ) that stormier high Tau weather (such as seen around sol 370, 420 and 510) are followed rapidly by an increase in dust deposition rate from ~0.2% per sol to ~0.3% per sol. I would assume that the much more severe dust levels we are now seeing would result in higher deposition rates fairly soon but we'll only know for sure once it happens.


Also Pavel's comment on night time temperatures is correct - at Tau=2 night time minimum temperatures would be about 15-20 degrees warmer IIRC and I'd expect that Tau-4 would improve that again. The effect is the similar to that seen here on earth where cloud cover raises night time temperatures.

That said the stuck heater on Oppy means she draws a bit more juice than Spirit. Again IIRC the heater in question draws 15watts and is activated if the atmospheric temperature falls below -52C and stays on until it warms up past -42c - they use Deep Sleep to keep it off during the night however I think they still have to live with it being stuck on for at least two hours per Sol under the best conditions so Oppy needs about 30 Whr per Sol more than Spirit.

Posted by: john_s Jul 5 2007, 11:53 PM

Here's another nice site for amateur images of Mars, and other Mars news:

http://elvis.rowan.edu/marswatch/images.php

John.

Posted by: slinted Jul 6 2007, 12:22 AM

Dr. Lemmon has an update on his http://www.lpl.arizona.edu/~lemmon/mer_dd.html, with some specific tau figures:

QUOTE
New, sol 1244: The recent dust storm activity has been intense for both rovers. Opportunity experience optical depths of (starting sol 1215) 1.3, 1.5, 1.7, 2.2, 2.6, 3.0, 3.3, 2.7, 3.1, 4.0, 4.1, rising from a background of 1.0. Spirit's opacity remained near 0.9 until starting on 1239 it went to 1.0, 1.0, 1.2, 1.3, 1.6, 2.4, 2.3. On sols 1239 and 1244, movies caught some dust devil activity. Sol 1240's movie did not see any activity. Recent sols have seen minor dust cleaning and deposition, but I'm not aware of major changes. The sol 1244 movie shows a much more indistinct horizon. The winds at Meridiani, especially, have probably been quite intense at times.

Posted by: Pando Jul 6 2007, 03:20 AM

QUOTE (slinted @ Jul 5 2007, 05:22 PM) *
Dr. Lemmon has an update on his http://www.lpl.arizona.edu/~lemmon/mer_dd.html, with some specific tau figures:

Tau is 4.1 now!!! ohmy.gif

Posted by: fredk Jul 6 2007, 04:17 AM

QUOTE (Pando @ Jul 6 2007, 03:20 AM) *
Tau is 4.1 now!!!
That's a bit better than our estimate of 4.6 based on the 99% direct sunlight attenuation quoted in the Space.com story. From Lemmon's site it was 3.1 on sol 1223. Was that a sol 1224 figure, Pando?

Posted by: Astro0 Jul 6 2007, 05:24 AM

Just got some feedback that Sol 1225 Tau is 4.125.
Oppy is at 255Whr.

Pray!

Posted by: Stu Jul 6 2007, 05:30 AM

Murky sky... hang on in there, Oppy...


Posted by: Bobby Jul 6 2007, 05:52 AM

The dust storm has delayed Oppy from entering Victoria Crater for now:

http://www.jpl.nasa.gov/news/features.cfm?feature=1411

Posted by: djellison Jul 6 2007, 07:25 AM

What with the stuck shoulder joint heater, 255 is a lot worse for Opportunity than for Spirit

Doug

Posted by: Tesheiner Jul 6 2007, 10:59 AM

QUOTE (Astro0 @ Jul 6 2007, 07:24 AM) *
Just got some feedback that Sol 1225 Tau is 4.125.
Oppy is at 255Whr.

Pray!


Checked the imaging plan for sol 1226 and it's only composed of two or three tau measurements. It remember Spirit during mid-winter times and looks like the available power would be not enough to run other things.

Keep strong little rover!

Posted by: belleraphon1 Jul 6 2007, 11:54 AM

Dust storm.... high tau...... high winds.....

Knowledge always comes with a price......

Yes, hang in there little rovers......

Craig

Posted by: sattrackpro Jul 6 2007, 12:24 PM

There is an interesting article about dust storms on the hubble-site http://hubblesite.org/newscenter/archive/releases/2001/31/text/ - that foretells a possible second following storm. (Hope not!)

Here's the relevant excerpt:

After three months, the storm is beginning to wane. The planet's shrouded surface has cooled, and this allowed the winds to die down and the fine dust to begin settling. However, Mars is approaching the closest point of its orbit to the Sun. Once the atmosphere begins to clear, the return of unfiltered solar radiation may trigger additional high winds and kick up the dust all over again. This one-two punch has been seen in previous Mars storms for centuries.

The article is old - but could multiple storms be caused, or have been caused in this fashion with this episode?

Posted by: helvick Jul 6 2007, 01:03 PM

Multiple major storms do happen in some years - the Vikings saw two in 1977 for example.

Posted by: mhoward Jul 6 2007, 01:54 PM

At least she was still taking pictures on sol 1225, and the calibration target looks clean. It's now morning on sol 1226. Let's keep our fingers crossed...

http://www.flickr.com/photos/marscat/737827497/

http://www.flickr.com/photos/marscat/737827331/

Posted by: tedstryk Jul 6 2007, 01:57 PM

Speaking of Hubble, it will look at Mars near the end of this month to help with MARCI's calibration woes, but in the process, it may catch the aftermath of this.

Posted by: Analyst Jul 6 2007, 02:07 PM

QUOTE (mhoward @ Jul 6 2007, 01:54 PM) *
... and the calibration target looks clean.


Very clean I have to say. Probably better than before?

Analyst

Posted by: centsworth_II Jul 6 2007, 02:24 PM

QUOTE (Analyst @ Jul 6 2007, 10:07 AM) *
Very clean...

But almost no shadow. There's the rub. sad.gif

Posted by: hortonheardawho Jul 6 2007, 02:37 PM

colorized Spirit sol 1244 ( July 4, 2007 ) L0 1x2:

http://www.flickr.com/photos/hortonheardawho/738900848/

Just a guess.

Posted by: diane Jul 6 2007, 05:17 PM

QUOTE (Astro0 @ Jul 6 2007, 12:24 AM) *
Just got some feedback that Sol 1225 Tau is 4.125.
Oppy is at 255Whr.

Does anyone know what Oppy's power reserves were before the storm got bad? I assume she can withstand some days of low power input, if the batteries were well-charged before the Tau got so high.

She doesn't have to survive a whole martian winter on low power.... Hopefully just a few days.

Posted by: dvandorn Jul 6 2007, 06:07 PM

I'm actually a little more worried about Spirit than I am about Oppy. This dust is all still entrained in the atmosphere, it hasn't really started to fall out yet. I don't know why, but I have this gut feeling that Meridiani may collect less dust from this storm than Gusev eventually will. Maybe because there is less overall dust accumulation on the ground at Meridiani than there is at Gusev; it just feels like Meridiani doesn't collect dust as effectively as Gusev does. (Maybe Gusev's crater rim causes a large-scale swirl in the winds that tends to make dust collect within, while the lack of any such circulation patterns at Meridiani keeps it from getting dumped on nearly as much.)

I guess I'm thinking that the dust ought to have specific patterns of fallout, based on when in the year the storms occur and what the wind patterns are like at the time. It also may have something to do with your distance from where the storms start and how they grow. It just feels like, since Oppy was closer to this storm as it formed, it may actually get away with having less of the dust dumped on it than other places on the planet -- perhaps even halfway across the globe.

Also, rather obviously, the polar caps display a process in which dust is often sandwiched between layers of dry ice. It may well be that a majority of the dust pulled up during these major storms ends up being deposited at the fall/winter pole, to which the air is flowing and where the air is precipitating out and plating itself onto the ground. That would tend to make sense from a global circulation pattern perspective.

-the other Doug

Posted by: akuo Jul 7 2007, 12:26 AM

Some new information in this National Geographic http://news.nationalgeographic.com/news/2007/07/070706-rovers-dust.html.

Jacob Matijevic is confident of rover survival.

Posted by: kungpostyle Jul 7 2007, 12:41 AM

Jake seems confident;

best rover news I've heard in a couple of days!

Posted by: mhoward Jul 7 2007, 01:45 AM

A handful of sol 1226 images are online. Just solar-filter images so far.

Posted by: MarsIsImportant Jul 7 2007, 05:02 AM

Sol 1226...look how clean the rover looks!

http://qt.exploratorium.edu/mars/opportunity/navcam/2007-07-06/1N236754570EFF85R9P1962R0M1.JPG

Posted by: CosmicRocker Jul 7 2007, 06:40 AM

She looked very clean, but that image should be from sol 1223. I suspect she is still pretty clean, despite the dust storm.

It's nice to hear that somewhat positive news from national geographic. I can't help but wonder if this would have been more of a survivability issue for the rovers if they hadn't been cleaned by the earlier winds. I also can't help but wonder if such early, cleaning winds might be expected prior to a dust storm.

Posted by: Sunspot Jul 7 2007, 07:36 AM

www.spaceweather.com reports the storm has intensified and grown. blink.gif

QUOTE
MARS UPDATE: A late-June dust storm that delayed Mars rover Opportunity's descent into Victoria Crater has intensified and spread around the planet, reports veteran observer Jim Melka of St. Louis, Missouri. On July 6th, the view through Melkin's 12-inch telescope showed "a chain of five dust clouds over Mare Cimmerium," he says. "One cloud is very close to the location of the Opportunity's twin, Spirit." Stay tuned for updates.

Posted by: djellison Jul 7 2007, 07:55 AM

Strong winds with the storm mean that Opportunity's going to be VERY clean as long as we don't catch a big chunk of dust when...er...the dust settles, as it were smile.gif

Doug

Posted by: vikingmars Jul 7 2007, 12:11 PM

wink.gif As a reminder, here are the fully calibrated comparison pics showing the minimum of light level encountered by Viking Lander 1 on sol 324 (1977).
Tau was between 5 and 6 depending your reading sources...
Enjoy ! (if I may say...)

 

Posted by: Stu Jul 7 2007, 01:33 PM

Hey, welcome back vikingmars! Missed your gorgeous pics!

Just for my own interest, not claiming 1000% accuracy or anything, but there's a LOT less detail visible on them that hills...

( left: June 13th, right: yestersol. )


Posted by: deglr6328 Jul 7 2007, 01:39 PM

how do we know how high the winds are at the surface?

Posted by: djellison Jul 7 2007, 01:42 PM

Well - from the rovers we don't really. For dust to be leaving the rover it has to be 'higher' than normal. Orbital imagery can track dust, clouds etc and gauge wind speeds that way.

Just a bit of fun from the values on Mark's page. Looks like we might be seing the turn in the trend- but as you can see, Meridiani already fooled us once in that regard.

Doug

 

Posted by: belleraphon1 Jul 7 2007, 11:56 PM

QUOTE (MarsIsImportant @ Jul 7 2007, 01:02 AM) *
Sol 1226...look how clean the rover looks!

http://qt.exploratorium.edu/mars/opportunity/navcam/2007-07-06/1N236754570EFF85R9P1962R0M1.JPG


Yes.... but what goes up must come down. All that dust in the upper atmosphere has to settle out at some point..... and those beautiful solar panels make a nice target....... just hope there is a balance between dust deposition and wind cleaning events....

Worried....... stay warm little rovers.... hold on.............. if I could I would gently blow your petals clean...

Craig

Posted by: belleraphon1 Jul 7 2007, 11:59 PM

OK - doing a total inline quote is one thing - doing it with your own post is madness!
Pointless quote removed! - Doug



And shine a light on your petals!!!!!!!

Craig

Posted by: CosmicRocker Jul 8 2007, 06:24 AM

Yes, whatever goes up must come down, but thanks to the winds it also travels sideways. I guess it's kind of a crap shoot. As the forces blowing dust around this planet run out of energy, let us hope that most of the entrained dust falls somewhere else. Everyone, cross your fingers. cool.gif

Posted by: djellison Jul 8 2007, 02:56 PM

another sols info on Marks page.

 

Posted by: clt510 Jul 9 2007, 01:57 PM

QUOTE (djellison @ Jul 8 2007, 09:56 AM) *
another sols info on Marks page.
Thanks for posting this, but could you provide the URL link for these?

THX.

Carrick

Posted by: centsworth_II Jul 9 2007, 02:42 PM

QUOTE (clt510 @ Jul 9 2007, 09:57 AM) *
... could you provide the URL link for these?

http://www.lpl.arizona.edu/~lemmon/mer_dd.html
(The values are in the text at the top of the page.)

Posted by: Tesheiner Jul 9 2007, 04:10 PM

Let´s hope for this descending trend in the tau values.
Meanwhile, Opportunity´s imaging operations are limited to tau measurements only since sol 1226. Same is expected/planned for tosol (1229) and tomorrow.

Posted by: CosmicRocker Jul 10 2007, 04:55 AM

The early trend is in the hoped-for direction, but Dr. Lemmon's page still has no new tau values as I go to sleep tonight.

QUOTE
New, sol 1249: The recent dust storm activity has been intense for both rovers. Opportunity experience optical depths of (starting sol 1215) 1.3, 1.5, 1.7, 2.2, 2.6, 3.0, 3.3, 2.7, 3.1, 4.0, 4.1, 3.7, 3.0 (to sol 1227-sol 1228 data aren't due until 1229 PM due to energy conservation measures from weekend plan), rising from a background of 1.0. Spirit's opacity remained near 0.9 until starting on 1239 it went to 1.0, 1.0, 1.2, 1.3, 1.6, 2.4, 2.3, 2.1, 2.1, 2.4, 2.3 (to sol 1249). New, sol 1244: On sols 1239 and 1244, movies caught some dust devil activity. Sol 1240's movie did not see any activity. Recent sols have seen minor dust cleaning and deposition, but I'm not aware of major changes. The sol 1244 movie shows a much more indistinct horizon. The winds at Meridiani, especially, have probably been quite intense at times.


We don't have any imagery from sol 1229.
CODE
5. What EDRs are missing?

Missing EDRs by sequence number and image type:  (This compares the SSF requests
to actual EDR PDS image files.  The missing ones may not have made it off the rover
yet, may not have been processed by MIPL yet, or may not have been taken as requested.)

Sol   Seq.Ver  ETH ESF EDN EFF ERP Tot  Description
----- -------- --- --- --- --- --- ---- -----------
01229 p2685.15 2   2   0   0   2   6    pancam_tau
01229 p2687.15 4   4   0   0   4   12   pancam_wide_range_tau
01229 Total    6   6   0   0   6   18


It does not appear that sol 1230 will be very active.
CODE
4. What EDRs did we request?

Expected EDRs by sequence number and image type:

Sol   Seq.Ver  ETH ESF EDN EFF ERP Tot  Description
----- -------- --- --- --- --- --- ---- -----------
01230 p0099.01 2   0   0   2   0   4    navcam_stereo_1_bpp_no_actuation
01230 p1550.01 2   0   1   0   0   3    navcam_tau
01230 p1550.01 0   0   0   0   0   0    navcam_sun_pri_57
01230 p2685.15 2   2   0   0   2   6    pancam_tau
01230 p2687.15 4   4   0   0   4   12   pancam_wide_range_tau
01230 Total    10  6   1   2   6   25


Sol 1231 is not a high energy consumption day, either.
CODE
4. What EDRs did we request?

Expected EDRs by sequence number and image type:

Sol   Seq.Ver  ETH ESF EDN EFF ERP Tot  Description
----- -------- --- --- --- --- --- ---- -----------
01231 p1550.01 2   0   1   0   0   3    navcam_tau
01231 p1963.06 2   0   0   2   0   4    navcam_tracks_loco_pri57
01231 Total    4   0   1   2   0   7


I am still optimistic that it is getting better for our rovers. cool.gif

Posted by: Pando Jul 10 2007, 06:33 AM

QUOTE (CosmicRocker @ Jul 9 2007, 09:55 PM) *
The early trend is in the hoped-for direction, but Dr. Lemmon's page still has no new tau values as I go to sleep tonight.

I am still optimistic that it is getting better for our rovers. cool.gif

2.9. So am I smile.gif

Posted by: djellison Jul 10 2007, 07:17 AM

Ignore the last Opportunity point - that's my guess, not an actual value.

I THINK...(well, guess) that we're closer to the 400 whr level rather than the 255 whr level now.

Doug


 

Posted by: jaredGalen Jul 10 2007, 09:54 AM

Out of curiosity, to reach Tau levels as we saw here (e.g. 4.0) would it typically take a storm to throw it up?

As such, would there be globally increased wind levels? Or can the storm be localised and kick the dust up into the higher atmosphere, leaving regions further from the storm with normal winds (virtually none) but high Tau? I don't know how low atmospheric pressure affects all that.

While high Tau is bad for solar junkies like Oppy and Spirit, will these events have helped glean a better understanding of mass air movement on Mars? What will they be trying to learn from the past few weeks?

Sorry for all the questions, guess I'm just thinking out loud....

Posted by: Tom Tamlyn Jul 10 2007, 02:38 PM

During Monday's Phoenix Mission press conference, Doug McCuistion, NASA's Mars Exploration Program manager, gave a brief but upbeat report on Opportunity's ability to survive the storm. I thought I also heard him say that Opportunity could function at a power level of about 100 watts. (It appeared later on that at least one reporter interpreted the 100 watts comment as referring to Phoenix, but I recall it as relating to the rovers).

That's a lot lower than the approximately 270-80 watt figure that's been discussed here as the rover's survival threshold. I assume that a good deal of the difference is represented by the fact that less power (no power?) ihttp://news.nationalgeographic.com/news/2007/07/070706-rovers-dust.html

Aside from heating, does anyone know what functions require power (and how much) for minimum survival? Does the rover draw no power at all during Deep Sleep?

TTT

Edit to fix typo.

Posted by: centsworth_II Jul 10 2007, 02:48 PM

QUOTE (Tom Tamlyn @ Jul 10 2007, 10:38 AM) *
I thought I also heard him say that Opportunity could function at a power level of about 100 watts.

He did say that. But it's more like "stay alive" than "function".
I think the only thing Opportunity would be doing at that power
level would be recharging. I don't know about heating. Has
deep sleep been used during the day? I envision it as a
deep sleep/recharge situation.

Posted by: Pando Jul 10 2007, 03:56 PM

To cut down power consumption, they would also need to reduce communication windows.

Posted by: Tom Tamlyn Jul 10 2007, 04:29 PM

Emily has posted a http://www.planetary.org/blog/article/00001029/ on her blog, with a full transcript of McCuistion's comments.

Most intriguing was this, which I had forgotten: "We have the ability to charge the batteries below 100 Watts. We can do imaging even below 100 Watts. So we can select the instruments we want; we don't communicate with the orbiters as frequently."

Emily has also promised to try to obtain more information.

TTT

Posted by: jaywee Jul 10 2007, 06:19 PM

QUOTE (Tom Tamlyn @ Jul 10 2007, 06:29 PM) *
Emily has also promised to try to obtain more information.


Emily, could you also ask (or anyone else) how the storm affects the surface day/night temperatures ?

jv

Posted by: MarsIsImportant Jul 10 2007, 07:08 PM

I've been looking for images of the magnets on the rover. I found a few; but I wish I could find a whole lot more.

These are the most recent images downloaded in order.

June 27th, 2007

http://qt.exploratorium.edu/mars/opportunity/micro_imager/2007-06-27/1M236222506EFF85R9P2976M2M1.JPG

July 1st, 2007

http://qt.exploratorium.edu/mars/opportunity/micro_imager/2007-07-01/1M236222650EFF85R9P2976M2M1.JPG

July 3rd, 2007

http://qt.exploratorium.edu/mars/opportunity/micro_imager/2007-07-03/1M236754439EFF85R9P2936M2M1.JPG

July 9th, 2007

http://qt.exploratorium.edu/mars/opportunity/micro_imager/2007-07-09/1M236754439EFF85R9P2936M2M1.JPG

As you can see, the wind is blowing some of the magnetic particles off of the magnets. I think that is an indicator of just how strong some of these winds must be.

Posted by: OWW Jul 10 2007, 07:46 PM

The first two are both from Sol 1217 and the last two are the same picture, from sol 1223.
So there is no evidence for more than one gust.

Posted by: djellison Jul 10 2007, 08:13 PM

Yup - raw images 101. The date something appears at the Exploratorium has little relation to when it was actually taken. The file name shows you when it was taken

1M236222506EFF85R9P2976M2M1

That's the time tag in red.



Doug

Posted by: Tom Tamlyn Jul 10 2007, 08:21 PM

jaywee,

Helvick, the forum expert on Martian solar power, briefly discussed the effect of dust on surface temperature http://www.unmannedspaceflight.com/index.php?s=&showtopic=4375&view=findpost&p=94286 (post #20, responding to http://www.unmannedspaceflight.com/index.php?s=&showtopic=4375&view=findpost&p=94279).

Of course it would also be great to hear what the Mars weather scientists are learning and expect to learn about this storm from the instruments in orbit.

TTT

Posted by: MarsIsImportant Jul 10 2007, 08:25 PM

QUOTE (OWW @ Jul 10 2007, 02:46 PM) *
The first two are both from Sol 1217 and the last two are the same picture, from sol 1223.
So there is no evidence for more than one gust.


I wasn't suggesting evidence for any more that one major gust. Actually we don't know whether it was just one gust...just one time interval when the change occurred. My point was that it was strong enough to clean the magnets significantly.

BTW the red tag continues to confuse me. They just look like a lot of number to me. unsure.gif

Posted by: djellison Jul 10 2007, 08:27 PM

http://midnightmarsbrowser.blogspot.com/

Get it.

Be confused no more.

smile.gif

Doug

Posted by: CosmicRocker Jul 10 2007, 08:58 PM

I just noticed this http://www.aviationweek.com/aw/generic/story.jsp?id=news/aw070907p2.xml&headline=Rover%20Ready%20for%20Dangerous%20Descent%20After%20Dust%20Storm&channel=space (Rover Ready for Dangerous Descent After Dust Storm) It seems to have a little new information about the dust storm and operations planned for inside the crater.

QUOTE
"For several sols [Martian days] we saw the opacity ["tau levels"] increasing at a rate of about 0.3/sol on Opportunity. It peaked at about 3.3, which is by far the highest value we have seen to date for either rover," says Squyres. But late last week, it was back down to 2.66--which is a large and sudden drop, indicating dust levels are highly variable.

Posted by: elakdawalla Jul 10 2007, 09:16 PM

Hi guys, I went to the Mars meeting at Caltech today and planned to get some answers but had to leave because I wasn't feeling well. I did catch Ray Arvidson before I left and asked him about the 100-Watt number and he said that was an error. A woman with him said she thought the number was more like 280 or 290.

--Emily

Posted by: Ant103 Jul 10 2007, 09:18 PM

Hi all smile.gif

A few times without posting because I've broken my wifi pcmcia card (thanks to gravity who have made fallen my laptop mad.gif ). The problem is now solve.

I learned that a dust storm hit our rovers.... And Olivier made us a little visit wink.gif

So, a picture I've made showing the inversion phenomena through the sky during a dust storm :
http://astrosurf.com/merimages/Opportunity/Images_en_couleur/Temp%EAte-Sol1224.jpg

And here, a color panorama of Victoria crater during the storm :
http://astrosurf.com/merimages/Images_opportunity-2007.html#Sol1224

In expecting that the storm will not during a lot of time unsure.gif

It's a pleasure to read you at new smile.gif

Posted by: Tman Jul 10 2007, 09:19 PM

QUOTE (MarsIsImportant @ Jul 10 2007, 10:25 PM) *
BTW the red tag continues to confuse me. They just look like a lot of number to me. unsure.gif

http://marsrovers.jpl.nasa.gov/gallery/edr_filename_key.html on the MER homepage explains the whole image code.

Posted by: helvick Jul 10 2007, 10:12 PM

That 255 whr figure for Sol 1225 is bugging me (Sorry Astr0 - feel free to object right back smile.gif )

I calculate that at a Tau of 4.1 on Sol 1225 for Opportunity she should have generated around 310Whr.

All of the other numbers that I've seen recently indicate that the insolation model I'm using underestimates the real values by 10% or so ( e.g. on sol 1221 @ Tau=3.3 the MER team have published a value of 402 Whr when I estimated about 360 Whr ). That would make me expect a real value of about 340 Whr if the Tau value of 4.1 is correct. Furthermore I really suspect that there was at least one small (5% or so) cleaning event sometime between Sol 1211 and 1220 which would put the number closer to 355Whr.

The most likely reason for this is that the diffuse Insolation model I'm using becomes increasingly unreliable as Tau rises past ~3 but it is also possible that the 255 Whr number isn't accurate. I'm also very surprised at Opportunity being able to function at all at that level, my understanding all along has been that 270-280Whr is extremely marginal for her given her stuck heater.

Very much looking forward to published numbers from the team.

Posted by: Floyd Jul 10 2007, 10:52 PM

QUOTE (MarsIsImportant @ Jul 10 2007, 04:25 PM) *
BTW the red tag continues to confuse me. They just look like a lot of number to me. unsure.gif


The code is explained http://qt.exploratorium.edu/mars/opportunity/README. wink.gif

Edit: sorry didn't see Tman's post as was reading the previous page.

Posted by: fredk Jul 11 2007, 12:06 AM

QUOTE (helvick @ Jul 10 2007, 10:12 PM) *
That 255 whr figure for Sol 1225 is bugging me
Well, we had that report that began this thread that the direct sun was attenuated by "nearly 99%" (tau = 4.6), with power at 280 Whr. The report was dated the 5th (sol 1225), though the sol is not mentioned in the article. Does that fit your model better?

The more recent data show a peak at 4.1, so 4.6 seems to have been an error. I suppose at times like this with everyone wanting tau values, numbers get out that aren't very accurate. Let's hope the clearing trend continues!

Posted by: hendric Jul 11 2007, 05:14 AM

Is it possible that the Tau reading is just a single point on a line, ie the Tau could be 4.6 now, but could be lower or higher before and after that reading. Tau comes from looking at the sun, right? So power produced could be slightly off from what you expect because the dust isn't consistent either across the sky, or from morning to evening.

Posted by: edstrick Jul 11 2007, 10:51 AM

high dust opacity drops daytime temperatures, but raises nighttime temperatures.

Local dust storms, if strong, show strongly convecting or at least dynamically churning clouds, often with some mixed-in condensation clouds, as seen from orbit. They can probably be quite opaque, but then the dust spreads out and disperses, like the storm that happened shortly before Beagle and MER's arrived.

Globe-encercling storms have been observed from orbit in development phase 3 times (2 viking orbiter storms and the 2001 storm), and once in the decay phase (the greatest of all, the 1971 global storm: Mariner 9.) Storm heating probably has a massive "ripple" effect on the adjacent atmosphere, as well as strongly boosting global atmospheric thermally-driven tidal oscillations, and can probably cause unusually strong winds even in non-storm-dust affected areas before the dust arrives. Areas near an active storm may plausibly have such strong induced winds that there is strong local dust scouring and lifting, causing a propagation of the main storm, starting solar heating of the newly raised dust in a sort of chain-reaction effect.

We just don't really understand the meteorology of storms and their growth. Vikings got some good photography at intervals, as well as infrared thermal mapper data. The 2001 storm was before Odyssey's arrival, I think but had good coverage by MGS's wide angle cameras and the thermal infrared spectrometer. With the wide angle cam on recon orbiter and the climate sounder, we're getting our first meteorology instrument look at a big storm :-) I hope to hell the've switched the instrument back into scanning mode for the storm.

Posted by: Pertinax Jul 11 2007, 12:29 PM

QUOTE (hendric @ Jul 11 2007, 01:14 AM) *
Is it possible that the Tau reading is just a single point on a line, ie the Tau could be 4.6 now, but could be lower or higher before and after that reading. Tau comes from looking at the sun, right? So power produced could be slightly off from what you expect because the dust isn't consistent either across the sky, or from morning to evening.


I would be strongly suspicious of any answer other than 'absolutely'.

The dust in the atmosphere certainly varies on short time scales -- they do on earth. Also, as you noted the extinction of sunlight would be greater for lower sun angles than higher for any given tau, as the effective optical depth increases with a lower sun (sun having to shine though a greater volume of air & dust). I have wondered myself how for a constant tau the sky appearance (including of course scattered light) would vary.

FWIW: http://marswatch.astro.cornell.edu/Bell_etal_SkyColor_06.pdf

-- Pertinax

Posted by: helvick Jul 11 2007, 01:56 PM

Thanks for the input folks.
The MER team's Tau values into account the solar zenith angle and the resulting increase in air mass as do my calculations for beam insolation. You can see this in the published Tau charts - the air mass numbers and DN's vary as they should with the changes in the local true solar time of the Pancam shots the readings are based on and the resulting Tau values are pretty consistent throughout each sol (on the occassions that multiple readings are taken)

However even though they are consistent there is definitely a daily cycle - Tau (generally) increases slightly over the course of a normal sol and then clears up slightly again overnight. Whether this cycle is more or less pronounced during a storm I can't say but for the vast majority of the year the variation is <0.1 over the course of each sol. To explain the variation I'm puzzled by we would need a variation of about 2.0 for about half the sol.

It is probable that part of the explanation is that very short time scale events (passing higher density dust flurries for example) are causing significant variations in Tau during the day.

Posted by: Pertinax Jul 11 2007, 02:06 PM

For fun, a question that I can probably dig for an answer for if there is not a quick one available here.....

Question: Is there engineering data available from the rovers (in the PDS I would presume) which reports the output from the solar arrays? If so, what is the temporal resolution (and averaging period if any) of the data?

It would be fascinating data if available in decent resolution.


-- Pertinax

Posted by: climber Jul 11 2007, 02:41 PM

I was wondering if we have, here on Earth, the equivalent of Marsian's dust storms?
For exemple, dusts coming from deserts that goes very high in our atmosphere where the pressure could be comparable to what it is on Mars?

Posted by: helvick Jul 11 2007, 02:43 PM

QUOTE
Pertinax wrote: It would be fascinating data if available in decent resolution.

I've been saying that for years. smile.gif

I don't think we'll see it any time soon unfortunately. It's engineering data that doesn't directly feed into any science data (as far as I know) and since some of the engineering data skirts into ITAR terrain releasing any of it requires that lawyers clear it first. That's just asking too much for data that is only of marginal interest at this stage in the mission. It would be great if someone used the data as part of a paper (say on short time scale variations in atmospheric opacity) and got it published that way,

The temporal resolution was good enough for the team to be able to specify that Spirit's last major cleaning event happened at 13:20 local time (IIRC) so I think it's at least possible to get it down to 10 minute intervals.

Posted by: tty Jul 11 2007, 02:55 PM

QUOTE (climber @ Jul 11 2007, 04:41 PM) *
I was wondering if we have, here on Earth, the equivalent of Marsian's dust storms?
For exemple, dusts coming from deserts that goes very high in our atmosphere where the pressure could be comparable to what it is on Mars?


Desert dust certainly can spread quite far. For example a fair amount of the soil on Bermuda is very fine saharan dust accumulated over hundreds of thousands of years. However terran "weather" in almost all forms very largely happens in the troposphere. For example despite the vast amount of salt spray created continuously over the oceans essentially nothing gets into the stratosphere (otherwise the sky at twilight would be yellow from the Na and the ozone layer would be destroyed by the Cl).

About the only exceptions is material from volcanic eruptions and large impacts which gets injected into the stratosphere with consequent climate effects extending over years (dust in the troposhere is washed out by rain fairly quickly).

Posted by: djellison Jul 11 2007, 03:20 PM

Saharan dust landing on cars in the UK isn't uncommon - I remeber two distinct occurances of that in the past decade or so.
Meanwhile - updated to 1230/1250 actual figures

Massive kudos to Mark for putting these on line so quickly.

 

Posted by: Oersted Jul 11 2007, 09:22 PM

The Sirocco:

Some nice pics here of the dust blowing from the Sahara up towards Europe.

http://en.wikipedia.org/wiki/Sirocco

Posted by: djellison Jul 11 2007, 09:31 PM

Infact -thinking about it - I remember finding comedy in the fact that a Sirocco was dumping sand on my mums VW Sirocco. smile.gif

Doug

Posted by: climber Jul 11 2007, 09:43 PM

QUOTE (djellison @ Jul 11 2007, 11:31 PM) *
Infact -thinking about it - I remember finding comedy in the fact that a Sirocco was dumping sand on my mums VW Sirocco. smile.gif
Doug

dd.gif Did any DD cleaned it up? biggrin.gif

Posted by: J.J. Jul 11 2007, 09:44 PM

A similar phenomenon we have here is "muddy rain"; it isn't really muddy, of course, but it is rich enough in dust that was lofted into the atmosphere in arid West Texas and deposited here to leave a significant film on one's car.

Posted by: Astro0 Jul 12 2007, 03:20 AM

'helvick' said that figure is "bugging me".

Hi Helvick,
That number came straight from someone on the MER team.
I'm sure that there's room for error though.
Astro0

Posted by: fredk Jul 12 2007, 03:44 PM

The latest navcam shows several changes in the tracks - the wind's been a-howlin' at Meridiani. And the shadows are much stronger now! (These views are less than half an hour apart local time.)

http://marsrovers.jpl.nasa.gov/gallery/all/1/n/1224/1N236844860EFF85R9P1963R0M1.JPG
http://marsrovers.jpl.nasa.gov/gallery/all/1/n/1231/1N237464520EFF85R9P1963R0M1.JPG

Posted by: helvick Jul 12 2007, 04:38 PM

Thanks for the confirmation Astr0. I'm going to have to hope that this means that Tau was varying fairly dramatically that day. Otherwise I might have to accept I've been wrong. Oh The Shame! smile.gif

Posted by: OWW Jul 12 2007, 05:04 PM

According to this report on space.com the dust storm is still spreading.

http://www.space.com/scienceastronomy/070711_mars_dust.html
and
http://themis.asu.edu/dustmaps/

The enormous dust storm raging across Mars' southern half has begun to creep into the northern hemisphere as well, new satellite images reveal.

"This storm isn't as big or severe as the one in 2001," Bandfield said. "THEMIS and other orbiters can still see the surface, despite the continuing dust activity."

It's uncertain how long the current storm will last, but it probably won't disappear as quickly as it began. "Mars will remain dusty for at least a couple more months," Bandfield predicts.


Sounds like the rovers will remain power-starved for a Long time. mad.gif

Posted by: Ant103 Jul 12 2007, 05:58 PM

Good eyes fredk. I'm going to make an animation to show this more evident wink.gif

The Themis link is very good : hop! direct favourite biggrin.gif

Edit : gif is finish.



The is little material disturbing, particulary just behind the low-gain antenna.

Posted by: Shaka Jul 12 2007, 06:51 PM

QUOTE (OWW @ Jul 12 2007, 07:04 AM) *
According to this report on space.com the dust storm is still spreading.

Sounds like the rovers will remain power-starved for a Long time. mad.gif

Especially long if they read the scale bars in reverse.
What's wrong with this picture? http://www.space.com/php/multimedia/imagedisplay/img_display.php?pic=thmdust_24500-24599_02.jpg&cap=Infrared+images+from+NASA%27s+Mars+Odyssey+orbiter+show+how+the+dust+storm+is+blocking+sunlight+to+the+plaet%27s+surface.+Opacity+decreases+from+left+to+right+on+the+scale+bar.+The+purple+aeas+are+nearly+clear%2C+while+the+red+regions+show+roughly+a+two-thirds+reduction+in+sunlight.+Credit%3A+NASA%2FJPL%2FArizona+State+University

Posted by: fredk Jul 12 2007, 07:34 PM

It occurs to me after comments in the Spirit thread that even though the local times are very similar in the two navcams I posted above, the tau has dropped from around 4 to around 3 so the lighting is less diffuse now. That should account for some of the changes visible in the tracks, but not all.

Posted by: fredk Jul 12 2007, 09:45 PM

From http://www.lpl.arizona.edu/~lemmon/mer_dd.html Oppy is stable at tau = 2.9 as of sol 1231, but Spirit has climbed in the past few sols to tau = 2.8 on sol 1252, which is the highest Spirit has ever been.

I get the sense this could linger for some time. http://en.wikipedia.org/wiki/It_ain't_over_'til_the_fat_lady_sings

Posted by: MarsIsImportant Jul 12 2007, 09:56 PM

I think you are correct Fred. This storm is not over yet. It could last a few more weeks. These peaks keep rolling into new peaks for other areas of Mars. We don't how bad this will get. It appears to becoming a global storm. Yet as far as we know, it could start to settle down tomorrow.

I'm glad that the tau at Meridiani appears to be stable; but who knows what will happen next?

Posted by: Oersted Jul 12 2007, 10:08 PM

QUOTE (Ant103 @ Jul 12 2007, 07:58 PM) *
The is little material disturbing, particulary just behind the low-gain antenna.


On that gif the change in light diffusion in the shadow on the antenna is really obvious.

Posted by: edstrick Jul 13 2007, 06:57 AM

What Viking and Mariner 9 saw was that storm activity keeps popping up and regenerating as long as there are relatively clearer parts of the atmosphere.

Once circulation and recirculation of storm-dust has pretty much uniformly filled the atmosphere with some relatively uniform few tau of dust, temperature differences drop below levels needed to churn up more dust. The storm then transitions to a decay phase, with an atmospheric dust half life of something like a couple weeks. Maybe that's equivalent to one tau's drop per two weeks..

Viking had two dust storms in one year -- most unusual -- the second one started just after the decay of the first storm got dust levels down to maybe about tau=1.. the levels present before the first storm really started.

As I recall, the first storm was pre-perihelion.. late spring.. the second was in summer.

Posted by: djellison Jul 13 2007, 07:31 AM

talking of popping up again...

I've added a few bits - can you tell I was bored on the train yesterday smile.gif

 

Posted by: Reckless Jul 13 2007, 09:41 AM

Hi Doug
These graphs have been very helpful to get an idea of whats going on.
Thanks for finding Marks data so quickly and putting it on the site, nice new touches too but perhaps there should be more orange (dust) on the top half of the graph to match the Tau going up.

Roy

Posted by: OWW Jul 13 2007, 08:33 PM

Well, according to Mark Lemmon's site tau is now 3.3 for Spirit. Same as Oppy. Maybe it will stabilize around this value then.

Everybody says Martian dust storms begin in the summer. But what time of year IS it anyway? The official MER-site and the MMB both have very nice martian clocks, but no calendar!
Is it 'June', 'July' or 'August' now? And is there a comparison somewhere on the net with the 1971 and 2001 storms? In which 'months' did those storms start and decay?

Posted by: alan Jul 13 2007, 09:21 PM

The southern summer solstice was last week.

Posted by: Greg Hullender Jul 13 2007, 10:43 PM

For a Mars calendar/clock, I like Mars24:

http://www.giss.nasa.gov/tools/mars24/

--Greg

Posted by: elakdawalla Jul 13 2007, 11:23 PM

And here's a table showing some past and future Mars seasonal dates. I have always intended to add some past ones going back to Mariner days, but never got around to sitting down with Mars24 and plugging dates in to find all the solstices and equinoxes.

http://planetary.org/explore/topics/mars/calendar.html

The Mars dust storm season begins just after perihelion at around Ls = 260°, wich is 10° (that is, 1/36 of a year or 1/3 "month", whatever that means for Mars) before the summer solstice.

--Emily

Posted by: MarsIsImportant Jul 14 2007, 01:18 AM

Look at those drastic differences in the tracks after the new drive!

http://qt.exploratorium.edu/mars/opportunity/pancam/2007-07-13/1P237557300EFF85RZP2571L2M1.JPG

That's amazing. Does anyone know which days those tracks are from? I know the clear ones were just made.

Posted by: fredk Jul 14 2007, 03:19 PM

QUOTE (helvick @ Jul 10 2007, 10:12 PM) *
That 255 whr figure for Sol 1225 is bugging me (Sorry Astr0 - feel free to object right back smile.gif )

I calculate that at a Tau of 4.1 on Sol 1225 for Opportunity she should have generated around 310Whr.
Some updated numbers in http://marsrovers.jpl.nasa.gov/mission/status_opportunityAll.html#sol1220
QUOTE
The tau measurement as of sol 1225 is 4.12, resulting in a mere 280 watt-hours of array energy.
Also, some more details to add to the confusion about how much power Oppy needs to survive:
QUOTE
A tau measurement of 5.0 would result in approximately 150 watt-hours. If tau begins to approach 5.0, the team will have to begin deleting communications windows in order to conserve energy and keep from draining the batteries.

Posted by: mhoward Jul 14 2007, 04:53 PM

QUOTE (fredk @ Jul 14 2007, 03:19 PM) *
Some updated numbers in [url=http://marsrovers.jpl.nasa.gov/mission/status_opportunityAll.html#sol1220]the latest Oppy update


Before anyone worries unduly, we should remind everyone that the news updates usually lag behind. Sol 1225 was the peak tau (as far as we've been told). It's now early on sol 1234 (heh, neat), and the tau is lower than that, unless it's spiked back up in the last two sols.

Posted by: OWW Jul 14 2007, 05:00 PM

Actually....from mark lemmon's site:

Sol 1233B: Opacity B1233 was 3.8 but it got above 4 during the sol.

Continues to rise for both Oppy and Spirit. Unfortunately.

Posted by: mhoward Jul 14 2007, 05:14 PM

D'oh. Okay, I guess it has spiked back up. How unfortunate.

Posted by: fredk Jul 14 2007, 05:26 PM

Yeah, mhoward, I could have said "some updated old numbers".

Speaking of http://www.lpl.arizona.edu/~lemmon/mer_dd.html he also writes:

QUOTE
New sol 1233B: Special guest appearance by the first of several fast dust devil movies at Meridiani to characterize lifting near and beyond the crater rim.
What the heck does he mean by "lifting"? Lifting of dust as the storm subsides? It's not exactly subsiding! He says "fast dd movies" - does that mean they're looking for short time scale phenomena? Gusts of wind perhaps?? Any other ideas?

Posted by: CosmicRocker Jul 15 2007, 06:07 AM

Yeah, I saw those frames come down today and wondered, "are they doing DD movies at Meridiani?" I suspect all of the frames are not down, but some looked to be fast, and others were many seconds apart. We at least seem to have parts of two movies so far.

I thought I noticed some subtle, local brightness variations in the sky among the available raw navcams. Maybe some of our "above the horizon" image magicians can find evidence of dust being lifted from the ground. That's what I think was meant by lifting.

The storm is certainly not subsiding yet. Meridiani and Gusev are experiencing new peaks. Searching for some good news, it sounds as if the rovers have plans for tau values around 5,

Posted by: djellison Jul 15 2007, 09:33 PM

New record for Opportunity on B1234 of 4.2. Much kudos to Mark for keeping the figures updated despite being involved in a Phoenix ORT.

Doug

 

Posted by: nprev Jul 16 2007, 03:51 AM

Oh my...not good. unsure.gif I searched in vain for the latest amateur Mars obs of this storm...anybody have any updates? This data suggests regional enrichment.

Posted by: djellison Jul 16 2007, 07:14 AM

Damian Peach has put a few up at the BAA website ( www.britastro.org )

Doug

Posted by: OWW Jul 16 2007, 09:08 AM

I also found this site:

http://elvis.rowan.edu/marswatch/news.php

Click on images on the left.

Posted by: OWW Jul 16 2007, 09:30 AM

Some new info on the HiRise blog. From July 11th:

http://hirise.lpl.arizona.edu/HiBlog/?p=92#more-92

Some HiLights:

At this point, the storm is considered a "hemispherical event," meaning it's mainly affecting "only" half of the planet (the southern hemisphere, in this case). We have our fingers crossed that this will not expand and become a global event like the 2001 dust storm.

The CRISM instrument can measure the composition of the dust, for example, so we've helped them acquire extra images by canceling a number of our own images that would have been obstructed by the dust anyway.

While we wait to see what the dust does, our Targeting Specialists are scrambling to cancel observations and figure out where to take a chance and try imaging.

Posted by: Sunspot Jul 16 2007, 08:32 PM

From New Scientist: http://space.newscientist.com/article/dn12276-martian-dust-storm-continues-to-affect-rovers.html

QUOTE
Squyres points out that the dust clouds do appear to have a silver lining. "One side benefit of the high winds that have caused this dust storm is that they have done a wonderful job of removing dust from the solar arrays on both rovers," he says. Opportunity's solar arrays are cleaner now than they have been since its 25th day on Mars – nearly 3.5 years ago, he explains.

Posted by: ngunn Jul 16 2007, 09:35 PM

I'm still a bit worried. As I said before it all has to fall down and it won't be any less opaque when it does. If it's 'hemispheric' as opposed to regional then there is no escape from the debris. We will need a fortuitous late gust at the end of the storm to do the cleaning.

Posted by: alan Jul 17 2007, 12:25 AM

Hopefully it will all fall in the northern hemisphere

Posted by: fredk Jul 17 2007, 04:04 PM

The distant horizon is fading from view. Compare this sequence from sols 1225, 1233, and 1235, taken near the same local time:
http://marsrovers.jpl.nasa.gov/gallery/all/1/p/1225/1P236931207EFF85R9P2629L6M1.JPG
http://marsrovers.jpl.nasa.gov/gallery/all/1/p/1233/1P237639549EFF85W0P2688L6M1.JPG
http://marsrovers.jpl.nasa.gov/gallery/all/1/p/1235/1P237817092EFF85W0P2689L6M1.JPG

Still no word on tau for 1235, but tau was a bit higher on 1225 than 1233. Yet the horizon is hazier on 1233. This seems to suggest that the atmosphere was dustier at low altitudes on 1233, but a bit clearer overall. Is this due to dust settling? Or to new dust being kicked up from the surface?

Posted by: Pando Jul 17 2007, 06:17 PM

Things aren't pretty right now, my sources tell me that tau is about 5 and increasing.
Let's all hope Oppy survives this...

Posted by: climber Jul 17 2007, 07:36 PM

QUOTE (fredk @ Jul 17 2007, 06:04 PM) *
The distant horizon is fading from view.

So it is at Spirit's on sol 1255 as well...

Posted by: djellison Jul 17 2007, 07:41 PM

More than 5! NIGHTMARE.



I'll have to change the scale of the Y axis on my graph!!!

Posted by: imipak Jul 17 2007, 08:08 PM

QUOTE
More than 5! NIGHTMARE.

I'll have to change the scale of the Y axis on my graph!!!


It's much worse than that -- it also means I have to sit here hitting ^r on an innocent Dust Devil page when I should be looking after someone's network security...

I've been rather distracted since seeing your last Tau chart heading back upwards for the last few days.

Could anyone enlighten me as to the typical timescale (if there are such things with such a small sample set to work from) for a regional or hemispheral storm to develop into a global storm, if it decides to do so? Or even how long the Viking and 2001 global storms took to develop from this stage to their full extent?

fredk already quoted this from the last status update, but it bears repeating:

QUOTE
A tau measurement of 5.0 would result in approximately 150 watt-hours.


>8.

Posted by: ugordan Jul 17 2007, 09:10 PM

Ouch... What's the bare minimum of whrs Opportunity needs to survive and can it survive with less than that for a short period of time? 150 whrs? How about 100?

Posted by: ElkGroveDan Jul 17 2007, 09:12 PM

QUOTE (imipak @ Jul 17 2007, 12:08 PM) *
Could anyone enlighten me as to the typical timescale (if there are such things with such a small sample set to work from) for a regional or hemispheral storm to develop into a global storm, if it decides to do so?

The storm encountered by Mariner 9 in 1971 began in late September and didn't fully subside until December. So it wouldn't be unreasonable to think in terms of two months. Though we have no way of knowing what portion of that storm had tau of 5 or greater. Still, it could be bad and it could be long.

Posted by: Ant103 Jul 17 2007, 09:35 PM

Fuzy horizon, dark ground, too red skies,
I request for clearer days.


 

Posted by: alan Jul 17 2007, 09:59 PM

Damn, the winds must be really picking up. ohmy.gif

Posted by: MarsIsImportant Jul 17 2007, 10:01 PM

This is bad...very, very bad. The worst part about it is the wait for information.

This is like having a family member in the hospital and not knowing whether they are going to make it.

Posted by: OWW Jul 17 2007, 10:15 PM

http://www.unmannedspaceflight.com/index.php?showtopic=821

Funny then. Not funny in THIS situation IMHO. sad.gif

Posted by: Sunspot Jul 17 2007, 10:52 PM

These could be the last pictures Opportunity transmits:

http://qt.exploratorium.edu/mars/opportunity/navcam/2007-07-17/1N237728274ESF85W0P1569L0M1.JPG

Posted by: djellison Jul 17 2007, 11:07 PM

I have a fair ammount of confidence that even with a couple of weeks of <200whrs essentially out of touch all together - the vehicle would be recoverable once the tau gets back to <3. It's summer, it's warmer at night, perhaps the MiniTES lens will go (but it hasn't with some very cold nights so far) - but I'm quietly confident.

Doug

Posted by: ElkGroveDan Jul 17 2007, 11:20 PM

Speaking of lenses, I wonder what all this particle movement is doing to the hazcams. It's not uncommon in the US desert Southwest regions for autmobile windshields to become buffed and pitted in sandstorms. The MI has a cover, and the pancam can be pointed downward but those hazcams just have to sit and take it.

Posted by: djellison Jul 17 2007, 11:23 PM

Spirit's FHAZ's are filthy right now, that much is obvious.

Doug

Posted by: belleraphon1 Jul 18 2007, 12:31 AM

Tau 5! very scary.

I remember Mariner 9....... was just out of High School and wandering the hippie havens of the University of Akron.

That 1971 dust storm actually helped dispel the notion that Mars was just a larger version of cratered Luna but with a wisp of atmosphere. I will never forget seeing the "spots" materialize out of the settling dust...
which turned out to be the summits of the Tharsis volcanoes..... the dust storm of 71 helped to highlight those features. And a revolution in our understanding of Mars.

Now, 36 years later, we are seeing the effects of one of these storms from the ground. I cannot help but find this fascinating as well as scary.

But....

Hang in there, Little Rovers....

Craig

Posted by: fredk Jul 18 2007, 03:19 AM

From Lemmon's site, Oppy's at 5.0-5.2 (sol 1236), "estimate based on array energy due to a no-activity plan, and last data for a couple sols".

Hang in there, indeed.

Posted by: alan Jul 18 2007, 04:18 AM

Also from Lemmon's site

QUOTE
Roughly speaking, array energy scales with exp(-0.09 * tau - 0.05 * tau^2), ignoring dust on the arrays and Sun-Mars distance. That's model-based, but is consistent with Opportunity results.


edit: used the above to produce power estimates for Oppy, not sure how accurate they are.


Posted by: CosmicRocker Jul 18 2007, 04:29 AM

I'd be lying if I said I am not concerned, but I am not terribly worried at this point, either. Oppy has felt she had enough power to take some images through sol 1236, even though the images have decreased in number. Furthermore, she has transmitted tens of images, including those "dust lifting" movies taken on sols 1233-4 as recently as today (sol 1237), two sols into tau5 conditions.

They have apparently suspended imaging as of sol 1237 and are not planning activities for a while, I am guessing as a precautionary measure.

One thing that we all can feel happy about is that both rovers look to be as clean as whistles, and so are able to absorb as many photons as are able to penetrate the gloom. Being a die hard optimist, I was looking for other good news, and this is the best I could come up with. There has been a bit of a correlation between tau, as recently measured by Spirit, and that measured by Opportunity. Just look at Doug's graph. According to Dr. Lemmon's site Spirit has seen a slight decrease from it's recent peak tau, from 3.8 to 3.6. That was tosol. We might not, but then again we just might, see dust levels on this side of the planet do something similar. Let us pray that it doesn't get much worse.

Posted by: Tesheiner Jul 18 2007, 07:03 AM

Just as an example of how the current low power situation affects the rover activities, sol 1235 was initially planned to be a driving sol but only a few imaging sequences were executed, driving was cancelled. Imaging started around 10:54 local time and finished at 11:35; just 40 minutes of activities. sad.gif

If we compare that with, let's say, sol 1203, the difference is significant. That sol imaging activities started at 09:41am, followed by a 60m drive lasting from 12:35 to 14:04, and finished at 16:31; that means a rover alive and kicking during almost seven hours!

Hang in there girls.

QUOTE (CosmicRocker @ Jul 18 2007, 06:29 AM) *
Oppy has felt she had enough power to take some images through sol 1236, even though the images have decreased in number.
...
They have apparently suspended imaging as of sol 1237 and are not planning activities for a while, I am guessing as a precautionary measure.


Imaging during sol 1236 have been apparently cancelled too.

Posted by: djellison Jul 18 2007, 07:32 AM

yikes.

 

Posted by: Reckless Jul 18 2007, 08:30 AM

Yikes indeed

And I think it would look even worse with the figures for the previous month in, a nice flat line at first and then it would sky rocket.

It would not be a good idea to put a trend line on that curve as it would be too depressing. ohmy.gif

Roy

Posted by: Tesheiner Jul 18 2007, 08:35 AM

Think positive, we have a clean rover and summer temperatures. Things could be much worse with dirty solar panels and during winter times.

Posted by: OWW Jul 18 2007, 09:09 AM

I'm worried about the fact that the last 5.2 value is based on array energy only. Look at these images from Horton:

http://www.flickr.com/photos/hortonheardawho/831774782/

I get the impression there's more dust on the deck on sol 1235. What if the power is dropping because there's more and more dust deposition? unsure.gif

Posted by: Tman Jul 18 2007, 09:42 AM

From this image, I tend rather torward more dust coming along with the wind than from above. Anyway we will need "back side" wind after the clouds of dust are over, I think.

Rather such dust stroms on Mars than one from Earth http://tagesschau.sf.tv/sfvideo/view/173120/1 (click "Breitband (450 kbit/s)")

Posted by: jvandriel Jul 18 2007, 10:44 AM

Here is the development of the
Duststorm seen through the eye of Spirit.
Views taken with the L5 Pancam between
Sol 1216 and Sol 1255

jvandriel

 

Posted by: jaredGalen Jul 18 2007, 01:42 PM

Wow, that's pretty scary.
Saw it mentioned that summer temps might be kind to the rovers, but what is the primary part that, if failed, would stop a rover waking up in the morning.

Is it the WEB cooling down too much?

Posted by: djellison Jul 18 2007, 02:50 PM

5.2-5.5 guestimated from array power on Marks latest update.

Doug

Posted by: Tesheiner Jul 18 2007, 03:21 PM

Bad news. ohmy.gif

Posted by: djellison Jul 18 2007, 03:22 PM

Well - good news in so far as the vehicle is healthy enough to tell us the solar array output from which the figure has been derived.

Doug

Posted by: fredk Jul 18 2007, 03:26 PM

And, for those of you not reloading Lemmon's page every five minutes, also this:

QUOTE
The 2007 global dust event has been intense for both rovers. In addition to global dust, a small storm is parked on the Opportunity site. Spirit may or may not see a different regional storm.

Posted by: lyford Jul 18 2007, 05:20 PM

Pardon my ignorance, but if they do a deep sleep during the day to save power - would the batteries still charge? Or is that an automatic hardwired function?

Just wondering if they would even want to do that to conserver power to ride out the worst... unsure.gif

Posted by: Stu Jul 18 2007, 05:29 PM

It would be ironic and cruel beyond words if Oppy succumbed to this dust storm after all she's survived to get here. What an adventure she's had so far... Surviving technical difficulties and deadlines on Earth before launch, then surviving the fiery plunge thru Mars' atmosphere, the boing-boing of landing and the "hole in one" bounce into Eagle Crater... countless long treks across the Meridiani desert... getting stuck in Purgatory Dune... the loooooong drive south the Victoria... and now, just when she was days away from entering the crater, and fulfilling what many see as her destiny - to explore the interior of the huge martian crater - the Great Ghoul of Mars, that has claimed so many other probes, finally turns its gaze on little Oppy and stops her in her tracks...



Hang in there Oppy, don't look at the sky... ohmy.gif

Posted by: climber Jul 18 2007, 05:53 PM

Trying to think positive smile.gif
I'm wondering if, once the Storm will have receded, it'll be worth trying to re-image all the others landers (V1, V2, MPF) to see if we can see any clean-ups as we see on Spirit & Oppy. I'm not sure the differences in albedo will show up but it could be an idea to submit to MRO's team. Any thoughts ?

Posted by: Del Palmer Jul 18 2007, 06:14 PM

QUOTE (lyford @ Jul 18 2007, 05:20 PM) *
Pardon my ignorance, but if they do a deep sleep during the day to save power - would the batteries still charge? Or is that an automatic hardwired function?

Just wondering if they would even want to do that to conserver power to ride out the worst... :unsure:


The batteries are disconnected from the main power bus (electrically isolated) from the solar arrays during Deep Sleep. It is like pulling the plug out of the wall. You don't want to do that during the day, otherwise the batteries will not be charged. And assuming you decided to do such a thing, you would have to wait until solar array wake-up the next morning to come out of Deep Sleep...

Posted by: lyford Jul 18 2007, 07:08 PM

Thanks Del Palmer, that's what I was afraid of... unsure.gif

Posted by: Ant103 Jul 18 2007, 08:53 PM

I become te be more and more anxious about the rovers and especially for Oppy. sad.gif
I have the very bad sensation that the storm will not dicrease so quickly and will during a few month...

I have lots of feelings for the rovers and this could be a shock to broke definitly contact with them sad.gif

I want to say in french : tempęte, je commence ŕ en avoir ma claque, tu dégages de lŕ!!

Posted by: jamescanvin Jul 18 2007, 09:38 PM

QUOTE (Del Palmer @ Jul 18 2007, 07:14 PM) *
The batteries are disconnected from the main power bus (electrically isolated) from the solar arrays during Deep Sleep.


Ah, I'm glad sombody knows this. I've only ever been able to find reference that all *loads* are removed from the battery. As clearly something of the solar array power gets to the BCB* (as it is this power that tells the BCB to reconnect the battery in the morning) I was never sure if the battery could be charged while in deep sleep.

QUOTE (Del Palmer @ Jul 18 2007, 07:14 PM) *
You don't want to do that during the day, otherwise the batteries will not be charged.


Well unless the array power was less than the minimum 'do nothing loads', particuarly with the sholder heater, in which case the battery is not going to charge anyway. The issue is: do you want to conserve power in the battery or do you use every drop trying to stay alive...

QUOTE (Ant103 @ Jul 18 2007, 09:53 PM) *
I become te be more and more anxious about the rovers and especially for Oppy. sad.gif


Me too, only in the last few hours have I started to really worry, tau > 5 wow! sad.gif

James

* BCB = Battery Control Board

Posted by: MarsIsImportant Jul 18 2007, 09:52 PM

Well, we definitely don't want a dead battery while in deep sleep. If that happens, then I'm afraid it would be R.I.P. for the rover.

Posted by: jamescanvin Jul 18 2007, 10:00 PM

Actually, after thinking and reading more about this, I'm not sure it's actually possible to deep sleep during the day (unless day is like night, not impossible at the moment!) as deep sleep works by disconnecting the BCB and ends when the BCB is naturally repowered by the solar arrays at dawn (when ~0.2 Amps is generated), ending deep sleep whether you want it to or not.

James

Posted by: fredk Jul 18 2007, 10:08 PM

There are so many questions I could ask here - eg, if the batteries are receiving little or no charge from the arrays, but are fully charged to begin with, how long will they retain their charge? I'm also curious whether they've had any sort of "action plan" in place for this kind of scenario. More than anything, I'd like to hear the level of confidence that the folks in control are expressing at this time. The last we heard from Squyres a few days ago was pretty confident.

BTW, welcome back James!

Posted by: djellison Jul 18 2007, 10:10 PM

But - iirc - that heater only comes on if it's cold.

I was thinking that actually the situation might arise when it's better to leave the battery cut off because even at noon, the array output wouldn't be high enough to power the heater - BUT - citing Encyclopedia Roveranica (Roving Mars ) -

"It kicked in half an hour before midnight Mars time, and it didn't go away until about 1000 the next morning. And whatever was responsible, it sucked more than 170 watt-hours of energy out of the batteries overnight"

Given that it's summer, and warm because of the dust - the arm heater might not kick in at all.

I don't know the specifics of the PCB, but is it intelligent enough to be preprogrammed for an expected wake up array voltage of X volts (when X is a lower number right now ) - which could be estimated to be 11am - then the master sequence for the day is sleep all day, wake up for the earliest Odyssey pass at which point you both uplink for the next day and downlink for that day, and then enter deep sleep till 19 hours later.

Doug

Posted by: helvick Jul 18 2007, 10:19 PM

QUOTE
Well unless the array power was less than the minimum 'do nothing loads', particuarly with the sholder heater, in which case the battery is not going to charge anyway. The issue is: do you want to conserve power in the battery or do you use every drop trying to stay alive..

This is close to happening. IIRC the stuck heater draws 15 watts unless she is in Deep Sleep mode. With Tau between 5.2 and 5.5 she's would generate ~ 120-150 Watt hours over the entire 12 hours of sunlight with a peak output around 18-22 watts. That doesn't leave much to go around for basic housekeeping, let alone to top off the batteries, take images and phone home.

Edited to add: Just noticed Doug's comment re the heater. Doh!, I'd forgotten that and it is quite likely that the temperature is high enough around the middle of the day to keep it off so that's a relief.
Also with reference to James Canvins comment regarding the wakeup current - I thought that wake up current was 2.0 amps which would keep it asleep until quite late in the day. I don't know what the panel output voltage range is but assuming it is only 10v then it would only just rise above 2A at the moment.

Posted by: imipak Jul 18 2007, 10:41 PM

QUOTE (Stu @ Jul 18 2007, 06:29 PM) *
...the Great Ghoul of Mars, that has claimed so many other probes, finally turns its gaze on little Oppy and stops her in her tracks...



HELLO, UMSF.COM.

LONG TIME LURKER, FIRST TIME POSTER...



With apologies to Terry Pratchett.

Posted by: elakdawalla Jul 19 2007, 01:42 AM

I'm doing some research to write about the storm and just thought I'd share some now-comical quotes from http://www.planetary.org/news/2007/0131_Mars_Exploration_Rovers_Update_Spirit.html regarding tau values measured by Spirit:

QUOTE
When the tau levels rise to 1, it limits the activities the rovers can perform and values of 2 or greater can be fatal. During most of Spirit's mission on Mars, tau values have ranged anywhere between 0 and 1. Not surprisingly then, there was real concern over the holiday weekend about whether or not Spirit was going to make it to its anniversary when the tau suddenly rose to .9 and then tipped to 1 at the end of December, and the rover's power levels began dropping....On Sol 1066 (New Year's Day 2007), the tau rose to 1.136 causing the rover's solar array energy to drop to a low 276 watt-hours, a level it had experienced briefly before in the depths of winter at Low Ridge....Once the engineers at JPL reanalyzed Spirit's power situation, they realized the rover could survive on less power now that spring was moving in. "For this time of year -- when temperatures are getting warmer and it's not getting super cold at night -- the amount of power that Spirit needs for survival is considerably less than it was in the wintertime. What the rover needs to survive in winter is something between 200 and 250 watt-hours, whereas now we can survive on something less than 200 watt-hours, so even with relatively low power numbers we're able to safely operate the vehicle and get lots done," Squyres explained.

How naive we were...I'm thinking of you, Opportunity, hunkered down under storm-darkened skies...

--Emily

Posted by: Del Palmer Jul 19 2007, 01:44 AM

QUOTE (fredk @ Jul 18 2007, 11:08 PM) *
There are so many questions I could ask here - eg, if the batteries are receiving little or no charge from the arrays, but are fully charged to begin with, how long will they retain their charge?

The self-discharge rate for the batteries is <5% per month - not something the MER team should be concerned about. smile.gif

Posted by: Del Palmer Jul 19 2007, 01:55 AM

QUOTE (djellison @ Jul 18 2007, 11:10 PM) *
I don't know the specifics of the PCB, but is it intelligent enough to be preprogrammed for an expected wake up array voltage of X volts (when X is a lower number right now ) - which could be estimated to be 11am - then the master sequence for the day is sleep all day, wake up for the earliest Odyssey pass at which point you both uplink for the next day and downlink for that day, and then enter deep sleep till 19 hours later.


Yes, the BCB is like the PRAM in a Mac - a self-contained programmable computer with non-volatile storage. You could change the wake-up voltage, however, it would be easier to use the master clock/timer to wake-up at a certain time instead of using solar array wake-up.

Posted by: Del Palmer Jul 19 2007, 02:01 AM

QUOTE (helvick @ Jul 18 2007, 11:19 PM) *
Edited to add: Just noticed Doug's comment re the heater. Doh!, I'd forgotten that and it is quite likely that the temperature is high enough around the middle of the day to keep it off so that's a relief.
Also with reference to James Canvins comment regarding the wakeup current - I thought that wake up current was 2.0 amps which would keep it asleep until quite late in the day. I don't know what the panel output voltage range is but assuming it is only 10v then it would only just rise above 2A at the moment.


You're both correct! Normally, the solar array wake-up current is 2 amps for 10 minutes. However, when waking from Deep Sleep, it is set to 0.2 amps.

Posted by: Del Palmer Jul 19 2007, 02:37 AM

QUOTE (jamescanvin @ Jul 18 2007, 10:38 PM) *
Ah, I'm glad sombody knows this. I've only ever been able to find reference that all *loads* are removed from the battery. As clearly something of the solar array power gets to the BCB* (as it is this power that tells the BCB to reconnect the battery in the morning) I was never sure if the battery could be charged while in deep sleep.

You're thinking of the BCB during normal operation. Just to clarify: the BCB is also off during Deep Sleep (only the master clock/timer are running), hence no recharging can take place - a circuit that measures the reference cells tells the BCB to power-up - this is where the 0.2 amps solar array wake-up value comes from.

Posted by: alan Jul 19 2007, 06:01 AM

Latest update for Spirit: tau at 4.0

Posted by: climber Jul 19 2007, 06:14 AM

To add a little bit more to our stress : is there one of the two rovers in restricted sols at this time ?

Posted by: MarsIsImportant Jul 19 2007, 10:22 AM

I was searching for more information about the current status of the rovers, but found this video instead--Unfinished Business. Please excuse the distraction at the beginning before the video starts.

http://www.space.com/php/video/player.php?video_id=060707Rovers_end

I certainly hope this global storm does not signify the end. At least, I'm not willing to give up hope, even if communications stop. It's possible communications could still be reestablished again when the dust settles.

Posted by: Tesheiner Jul 19 2007, 01:27 PM

QUOTE (climber @ Jul 19 2007, 08:14 AM) *
To add a little bit more to our stress : is there one of the two rovers in restricted sols at this time ?

Spirit is on restricted sols, but given the current situation it's not a big deal: plan for solX = plan for solX+1 = plan for solX+2 = tau measurement.
QUOTE (jamescanvin @ Jul 18 2007, 11:38 PM) *
James

Welcome back, James.

Posted by: fredk Jul 19 2007, 02:45 PM

QUOTE (elakdawalla @ Jul 19 2007, 01:42 AM) *
I'm doing some research to write about the storm and just thought I'd share some now-comical quotes from http://www.planetary.org/news/2007/0131_Mars_Exploration_Rovers_Update_Spirit.html regarding tau values measured by Spirit:
...
How naive we were...I'm thinking of you, Opportunity, hunkered down under storm-darkened skies...
Remember that that was spring, and this is mid-summer, so we need less power to survive now, since temperatures are higher. Also the panels are much cleaner now! At the time that article was written we were only recently reawakened from our winter sleep, when we had barely enough power to survive, and so no doubt a tau of 2 would have been fatal!

Posted by: Tesheiner Jul 19 2007, 03:23 PM

Latest update on the tau values by Mark Lemmon for Opportunity is 4.6-4.8 for sol 1238.
We are back below 5.0. Uff!

Posted by: climber Jul 19 2007, 03:32 PM

QUOTE (Tesheiner @ Jul 19 2007, 03:27 PM) *
Spirit is on restricted sols, but given the current situation it's not a big deal: plan for solX = plan for solX+1 = plan for solX+2 = tau measurement.

I was thinking about communications. If we communicate directly, that's no big deal as you says but if we use Odyssey we'll have news only every second day.

Posted by: jamescanvin Jul 19 2007, 03:33 PM

I never thorght i'd be glad to see a Tau of 4.6-4.8!

That should give about 200Whr if my maths is right. That is probably just about enough, right?

James

Posted by: djellison Jul 19 2007, 03:44 PM

Keeping it up to date smile.gif

Even with 200 Whrs - all I'd want to do is charge the battery. Figure out the times of day when solar-array wattage > non-deep-sleeping rover wattage requirements and just power up for those times and then shut down again. Be 'on' when the potential is for power-positive operations, be 'off' the rest of the time. Because if this storm has taught us anything it's that it can get worse again faster than it gets better.

Doug

 

Posted by: Edward Schmitz Jul 19 2007, 03:46 PM

There are still down links every day. It's just not in time to do planning.

Posted by: djellison Jul 19 2007, 03:58 PM

Actually - they've started culling them. According to Mark, they tried an uplink on 1237 to tell the rover to NOT to that afternoon's Odyssey pass- but the uplink didn't go through

(my best guess - an atmosphere rammed full of ferric dust does things to radio waves)

Doug

Posted by: jamescanvin Jul 19 2007, 04:10 PM

QUOTE (djellison @ Jul 19 2007, 04:44 PM) *
Even with 200 Whrs - all I'd want to do is charge the battery.


Oh sure, I wasn't suggesting they should actually do anything, except stay alive with those 200. Save any precious spare Whr's in the battery for a rainy dusty day.

Posted by: djellison Jul 19 2007, 04:20 PM

Back of envelope maths...

A full battery is 600 Whrs.

Basic spirit ops during winter were 240 Whrs

Opportunity currently 150-200 Whrs ( let's say average of 175 )

Battery Out In End
600 240 175 535
535 240 175 470
470 240 175 405
405 240 175 340
340 240 175 275
275 240 175 210
210 240 175 145
145 240 175 80
80 240 175 15
15 240 175 -50


etc etc


Doug

Posted by: climber Jul 19 2007, 04:27 PM

A few questions :
Do we know if there's a day/night effect on the storm? If yes, can this explain tau ups & downs?
Did we see this with Viking?
Are storms able to increase Tau at Phoenix landing latitude ?

Posted by: Ant103 Jul 19 2007, 06:35 PM

Spirit atmospheric observations following upadated with the Sol 1254, where we "see" Grissom Hill faintly :
http://astrosurf.com/merimages/Images_de_spirit-2007.html#atmopacite

And in addition, an animation showing Grissom Hill "immersion" through the thickness of the dust storm :



An other color picture, taken on Sol 1255 :
http://astrosurf.com/merimages/Spirit/Images_en_couleur/Tempete-Sol1255.JPG
In expecting that it wouldn't be the last color pic...

Posted by: deglr6328 Jul 19 2007, 06:56 PM

A full NEW battery is 600 W-hrs. These batteries are ~5 years old and have gone through >1200 discharge cycles. We're probably looking at more like 400 W-hrs max capacity now given that the cells show a ~30% charge capacity loss after 1000 cycles. That cuts a few days off the run-down-to-dead calculations. http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/38847/1/04-2590.pdf

Posted by: djellison Jul 19 2007, 07:31 PM

To be fair - it's more like 10.2 Ahrs down to about 8 Ahrs - so from 600 Whrs to 470 Whrs at the very worst - but given that it's not had 1000+ FULL cycles - but partial cycles, and in good power states, probably less than 1/3rd cycle per sol - I would argue for >500Whrs of battery capacity.

Doug

Posted by: jamescanvin Jul 19 2007, 09:07 PM

But the question is not how much charge the batteries can hold but how much they actually have right now. I doubt the batteries are fully charged at the moment!

Also I was under the impression that Oppy could get away with quite a bit thess than 240Whr during these warm summer nights?

So all in all I don't think we can make any guesses about how long a rover can hold out under these conditions, not to mention how quickly these conditions change. We just need to hope, each sol they survive is one sol closer to the end of the storm...

James

Posted by: fredk Jul 19 2007, 11:09 PM

QUOTE (Ant103 @ Jul 19 2007, 06:35 PM) *
In expecting that it wouldn't be the last color pic...
Indeed it wasn't the last colour pic - they've reshot that view on 1258, and the farthest hills are now http://marsrovers.jpl.nasa.gov/gallery/all/2/p/1258/2P238039046EFFAUCMP2688L7M1.JPG This is under tau = 4.0 skies.

Posted by: Oren Iishi Jul 19 2007, 11:50 PM

Would moving Oppy to a more advantageous tilt and direction to the sun help at all in this situation? I know it worked well for Spirit last winter but that was not under these kinds of elevated dust levels. I'm thinking this lilypadding technique might give Oppy just a few more watts and it could be just enough to get her though the storm. Any thoughts on this idea?

Posted by: elakdawalla Jul 19 2007, 11:52 PM

MARCI images of the storm, including many over Opportunity:

http://www.msss.com/msss_images/2007/07/19/

EDIT: Arg. I was going to make an animation of the nine-frame image at the bottom but their little white circle showing Opportunity isn't quite steady on the map -- it's going to take a little doctoring to make it look right, which I don't have time for right now...maybe tomorrow...or maybe one of you will beat me to it smile.gif

--Emily

Posted by: helvick Jul 20 2007, 12:32 AM

QUOTE (Oren Iishi @ Jul 20 2007, 12:50 AM) *
Would moving Oppy to a more advantageous tilt and direction to the sun help at all in this situation?

The quick answer is absolutely not.

The slightly longer answer is that once Tau rises past about 3 almost all of the solar energy (>95%) comes from diffuse light and that number passes 99% when Tau rises over 5. That means that the panels' orientation is irrelevant under these condtions - they could be turned upside down and pointed directly away from the sun and it would make almost no difference to the amount of power they generate.
Here's an example chart for Sol 1237 (Tau = 5.2 , Dust loading = ~15% power loss). Bear in mind that this is based on my version of the Applebaum and Landis version of the Pollack martian insolation model and I think that my model overestimates actual power levels by about 25% when Tau is at ~5. The very faint almost flat blue line at the bottom is the power generated by the direct beam insolation, the green line is the total diffuse insolation and the red line is the "theoretical max" that would be available if there were no atmosphere or storm interfering. The y axis is in (instantaneous) watts.

Posted by: Astro0 Jul 20 2007, 01:03 AM

None of the images in that sequence nor the circles are aligned properly.
Line up the circles and the background jumps. Line up the background and the circle jumps.
However, if you just animate them anyway, you get the idea of just how bad this storm has been.
A very big dust cloud sweeps around Oppy's location from left to right, then a big cloud comes from the south and seems to land of top before everything is obscured from view.

Astro0

EDIT: I've updated the image to blend out the missing data. Not perfect but it gives you an idea of what's happening.


File:750k

Posted by: elakdawalla Jul 20 2007, 03:03 AM

The baby gave me a little more time to work after all, so here's my version. I found that only one of the circles was seriously badly aligned, so I fudged that one and aligned all the images on craters as long as I could see them (none visible in the last image!) I also replaced the black gores with a slightly less distracting color.



This is reduced in size from the original. I'll get the original uploaded tomorrow when I try to put together a story on the storm. I've been in communication with various people and while people certainly are concerned about the rovers and the storm, honestly no one seems actually to be worried about their survival. I'd say that Opportunity's condition is "serious" but not "critical," in hospital parlance.

Gotta go rest the typing fingers now...

--Emily

Posted by: CosmicRocker Jul 20 2007, 04:17 AM

Wow, Astro0! I can't believe what I am seeing.

Posted by: edstrick Jul 20 2007, 06:13 AM

"...farthest hills are now almost completely invisible. This is under tau = 4.0 skies..."

Though the analysis of data will be more complicated than for sun images and for skylight data, the view of the hills gives an independent measure of dust opacity along a NEAR SURFACE line of sight, instead of integrated through the vertical height of the atmosphere. They are not necessarily the same.

Posted by: Astro0 Jul 20 2007, 06:17 AM

Here's another stretched version of the storm to show up more of the lower cloud detail.
Astro0


WARNING: File: 952k

Posted by: ugordan Jul 20 2007, 07:42 AM

What's with the wave-like effects that appear to correspond to MARCI's imaging strips and propagate to the east? I presume those are just imaging artifacts though they do look a bit like surface illumination effects?

Posted by: djellison Jul 20 2007, 08:12 AM

Remember - this isn't a snapshot of the whole planet at one time - it's slices of planet at 3pm local - and thus you get lighting effects from one side of each stripe to the other.

Doug

Posted by: ugordan Jul 20 2007, 08:24 AM

I'm aware of the slices, but I forgot to take into account the wide FOV the instrument has that encompasses a range of local times, not just 3 PM. Shame, the "waves" distract from the dust clouds visible in the animations Astr0 and Emily posted and almost give a feeling of wave nature to the storm. In case of the dust storm there's probably an additional factor of optical depth of the atmosphere when looking way off nadir.

Posted by: jamescanvin Jul 20 2007, 09:03 AM

Gusev remained at Tau = 4.0 for 1259, for those few not watching Mark's page closely.

Posted by: AndyG Jul 20 2007, 09:49 AM

Pre-storm, I was wondering whether the decision to go with a nuclear-powered MSL was wise in the light of the MER's solar-electric longevity.

I have no doubts now.

Andy

Posted by: helvick Jul 20 2007, 10:02 AM

QUOTE (edstrick @ Jul 20 2007, 07:13 AM) *
Though the analysis of data will be more complicated than for sun images and for skylight data, the view of the hills gives an independent measure of dust opacity along a NEAR SURFACE line of sight, instead of integrated through the vertical height of the atmosphere. They are not necessarily the same.

The standard Tau measurements are carried out at various times and adjusted to account for the transit through the additional air mass resulting from off zenith pointing e.g. take this extract from Spirit's published tau data
CODE
Product_ID                   ,   L_s, R_au,      Sol,    AM,     Flux,    TAU, Rel_err
"2P134460532ESF2700P2600L8M1",  15.1, 1.594,  90.703,  3.790, 179.723,  0.523,   0.003
"2P134522131ESF2700P2678L8M1",  15.5, 1.595,  91.397,  1.355, 576.685,  0.600,   0.011
"2P134525203ESF2700P2600L8M1",  15.5, 1.595,  91.431,  1.184, 647.670,  0.589,   0.009

The fractional part of the Sol field indicates the local time (4:52pm , 9:32am, 10:20am) at the time the measurement was taken, AM is the http://en.wikipedia.org/wiki/Airmasss approximately the secant of the Zenith angle at that time. The tau measurement is made by accounting for the additional air-mass and the expected Flux reading given the effective solar constant (derived from the R_au measurement - the distance from the sun).

As you say though this becomes increasingly tricky when tau is high and the senith angle is high - ie with nearly horizontal views to the horizon.

Posted by: Mongo Jul 20 2007, 01:25 PM

QUOTE (AndyG @ Jul 20 2007, 09:49 AM) *
Pre-storm, I was wondering whether the decision to go with a nuclear-powered MSL was wise in the light of the MER's solar-electric longevity.

I have no doubts now.

Andy

The reason that dust storms are so deadly at high tau is because critical parts of the rover get too cold, right? The lack of power is not a problem in itself, as the rover can hibernate.

So why not go with solar-electric power, plus insulation and a small radioisotope heat generator to keep the main body warm? Things like arms, that are not warmed by the heat generator but still need to be kept warm, would have the same system of heaters that the MERs do -- the difference being that those heaters would be the only electrical load during hibernation. I believe that even the worst dust storms should allow enough energy to keep those heaters going -- especially given the lower-atmosphere heating observed during dust storms.

The advantages of such a system would be lower total power-system mass (I think), lower development costs, and possibly a longer lifetime (going by the MER experiences) if, as I seem to recall, the reactor only has a several years lifetime.

Bill

Posted by: djellison Jul 20 2007, 01:27 PM

QUOTE (Mongo @ Jul 20 2007, 02:25 PM) *
the reactor only has a several years lifetime.


A couple of decades.

Doug

Posted by: MarsIsImportant Jul 20 2007, 02:44 PM

Another advantage of a nuclear powered MSL is that it can work at night. Dust storms would not slow progress, and continuous night studies could be a very significant development. The MSL could operate basically 24/7 if need be.

I do think there could be some additional advantages if a combined approach could be developed for future missions. Also, maybe a soft brush could be included to manually sweep clean any solar arrays. I also hope that better wheels are developed. I would think something could fairly easily be developed to last a few thousand miles worth of surface travel. The problem might be staying within weight constraints.

Posted by: akuo Jul 20 2007, 02:51 PM

QUOTE (MarsIsImportant @ Jul 20 2007, 02:44 PM) *
The MSL could operate basically 24/7 if need be.

I was wondering about this, and that's why I asked the MSL experts this question. http://www.unmannedspaceflight.com/index.php?s=&showtopic=4251&view=findpost&p=91425 tells us that it won't have the capability to operate 24h a day, because the batteries still need to be charged by the RTG. 7 hours each sol adds up to significantly more what the MERs do, though.

Posted by: MarsIsImportant Jul 20 2007, 03:00 PM

That's why a combined approach might be useful. It might be too late to change the MSL design; but I don't think it will be the last rover. Also, 7 hours per Sol is an average. If the batteries are fully charged, then I believe that it could operate longer.

With a combined approach, then closer to continuous 24/7 could be achieved. However, the batteries might not last as long. So there are multiple trade offs.

I just think it would be a waste to completely throw away the advantages of solar power. The MER proves the application of the technology. I just want a brush so that we don't have to wait for the wind to blow.

Posted by: djellison Jul 20 2007, 03:19 PM

Get rid of the brush, get rid of the arrays use an RTG and you've fine. And remember - there is another short-link in the chain. People. You can't have a rover that operates 24/7 - not least of all because you'd have to take floodlights with you - but also because you need downtime for the operations team to design the next sols sequence based on the results of the previous sequence. The downtime inbetween can be used a little like the rover's nights have been from time to time - APXS/Mossbauer integrations ( in the case of MSL - APXS integrations and the SAM suite )

You want to add arrays, a big arm with a brush ( which is more mass, more volume, more money )
That RTG is going to be producing X Watts, every hour of every sol, and that figure is more than is required to operate the vehicle. There isn't any sense in adding a further power source when you could spend the mass, volume and money elsewhere (like, a slightly larger RTG for instance). The very point of the RTG is that it gives a perfectly predictable, reliable power source for as long as you need it (over a primary mission of a martian year) - it's eliminates every down-side of the solar arrays in one - excuse the pun - sweep.
Doug

Posted by: maycm Jul 20 2007, 03:33 PM

I always wondered why they couldn't emulate a good strong gust of wind by drawing in some Martian "air" and using a method of blowing off the dust.

Locate a nozzle in the centre of the array in such a way that as it spins as it blows and you could cover a large percentage of the array. Likely only needs to be pretty small and lightweight too.

Posted by: MarsIsImportant Jul 20 2007, 04:00 PM

You don't need floodlights. You just use infrared sensors. There is a whole host of instruments that you don't need lights for. It all depends upon what kind of science you want the rovers to do. You are correct that only certain things can be done during the day. Yet, valuable measurements could easily be done at night with the right instrument package.

The trade off because of human limitations is a valid point. Yet, team shift management can solve a lot of those problems. The real problem with approaching 24/7 is a commitment of time and money. It could be done and, in my opinion, would be worth it. But getting funding for such a program would be a problem.

Posted by: OWW Jul 20 2007, 04:10 PM

NASA Mars Rovers Braving Severe Dust Storms:

http://www.jpl.nasa.gov/news/news.cfm?release=2007-080

On Tuesday, July 17, the output from Opportunity's solar panels dropped to 148 watt hours, the lowest point for either rover. On Wednesday, Opportunity's solar-panel output dropped even lower, to 128 watt hours.

Engineers calculate that skipping communications sessions should lower daily energy use to less than 130 watt hours.

A possible outcome of this storm is that one or both rovers could be damaged permanently or even disabled. Engineers will assess the capability of each rover after the storm clears.

Gulp... Only 128 Watt! sad.gif

Posted by: Floyd Jul 20 2007, 04:12 PM

http://www.jpl.nasa.gov/news/news.cfm?release=2007-080.



"On Tuesday, July 17, the output from Opportunity's solar panels dropped to 148 watt hours, the lowest point for either rover. On Wednesday, Opportunity's solar-panel output dropped even lower, to 128 watt hours."


"To minimize further the amount of energy Opportunity is using, mission controllers sent commands on Wednesday, July 18, instructing the rover to refrain from communicating with Earth on Thursday and Friday. This is the first time either of the rovers has been told to skip communications for a day or more in order to conserve energy. Engineers calculate that skipping communications sessions should lower daily energy use to less than 130 watt hours"

Posted by: OWW Jul 20 2007, 04:23 PM

Interesting quote from Richard Zurek:
http://www.jpl.nasa.gov/multimedia/audioclips/mer-20070720/

"If you're at the rover, for instance, sitting on the surface, and you're looking up at the sky, you're not going to see the sun's disk, even during the day because the cloud, the dust haze, is thick enough that the sunlight has been either absorbed or scattered."

How can this be? Spirit can still see the sun in those Tau images:
From Sol 1259 ( Tau 4 ):

Posted by: Ant103 Jul 20 2007, 04:28 PM

Hum... That's explain the form of the Sun, a little stretched, by I longer exposure than a normal-tau day, due to Mars rotation during it? huh.gif

Posted by: akuo Jul 20 2007, 05:50 PM

"This is, I think, one of the most significant challenges we've faced over this entire mission," Squyres told http://www.space.com/news/070720_rover_dust.html today. "The nature of the risk is well understood, but the magnitude of the risk is not. We simply don't know what's going to happen next."
"Whatever we do, though, the problem is not going to get much better rapidly," he said. "I think that we have a good chance. If Mars really wants to kill these vehicles it can, but we have a lot of things working in our favor."

Posted by: Del Palmer Jul 20 2007, 06:08 PM

QUOTE (MarsIsImportant @ Jul 20 2007, 04:00 PM) *
I just think it would be a waste to completely throw away the advantages of solar power. The MER proves the application of the technology. I just want a brush so that we don't have to wait for the wind to blow.

Solar power will continue to be used by missions that cannot afford the price of RTG goodness. Certainly, no NASA Mars Scout mission can afford an RTG.

Brushes are so 20th Century, how about an electrodynamic dust shield instead? smile.gif
http://science.nasa.gov/headlines/y2006/19apr_dustbuster.htm

Posted by: djellison Jul 20 2007, 06:10 PM

I saw videos of that electrostatic mechanism at the IAC'06 in Valencia - it was brilliant. Far FAR better than any mechanical system.

Doug

Posted by: Edward Schmitz Jul 20 2007, 06:49 PM

QUOTE (Mongo @ Jul 20 2007, 06:25 AM) *
So why not go with solar-electric power, plus insulation and a small radioisotope heat generator to keep the main body warm?


They are insulated and they already have had problems with over heating.

Posted by: Edward Schmitz Jul 20 2007, 06:51 PM

QUOTE (akuo @ Jul 20 2007, 07:51 AM) *
I was wondering about this, and that's why I asked the MSL experts this question. http://www.unmannedspaceflight.com/index.php?s=&showtopic=4251&view=findpost&p=91425 tells us that it won't have the capability to operate 24h a day, because the batteries still need to be charged by the RTG. 7 hours each sol adds up to significantly more what the MERs do, though.

The real advantage is time of day independance.

Posted by: Edward Schmitz Jul 20 2007, 06:56 PM

QUOTE (maycm @ Jul 20 2007, 08:33 AM) *
I always wondered why they couldn't emulate a good strong gust of wind by drawing in some Martian "air" and using a method of blowing off the dust.

Locate a nozzle in the centre of the array in such a way that as it spins as it blows and you could cover a large percentage of the array. Likely only needs to be pretty small and lightweight too.

I know folks who are working on the next gen of martian solar arrays. They are using panel vibrators to shake the dust off. Their testing under simulated martian conditions are showing that it should be able to keep the panels clean.

Posted by: climber Jul 20 2007, 07:17 PM

Meanwhile, even if kind of OT we get 2500 sols total today... and Spirit is very close to 100.000 pictures. smile.gif

Posted by: OWW Jul 20 2007, 07:36 PM

AND Spirit is only 20 sols away from beating Viking 2!

Back OT. From the space.com article:
If Mars really wants to kill these vehicles it can, but we have a lot of things working in our favor.

Question: what things? huh.gif

Posted by: paxdan Jul 20 2007, 07:48 PM

QUOTE (OWW @ Jul 20 2007, 08:36 PM) *
Question: what things? huh.gif

Rocket scientists biggrin.gif

Posted by: Del Palmer Jul 20 2007, 08:07 PM

THEMIS dust maps:
http://themis.asu.edu/dustmaps/

Posted by: Mongo Jul 20 2007, 08:22 PM

QUOTE (djellison @ Jul 20 2007, 01:27 PM) *
A couple of decades.

Doug

Really? I looked at the project website, and they were saying that the RTG was designed to provide an operating lifespan of 'a full Martian year'. The MERs are already at twice that timespan.

Bill

Posted by: djellison Jul 20 2007, 08:55 PM

It'll last for years and years and years - like NH's or the Voyager ones.

Doug

Posted by: ToSeek Jul 20 2007, 09:18 PM

QUOTE (Mongo @ Jul 20 2007, 04:22 PM) *
Really? I looked at the project website, and they were saying that the RTG was designed to provide an operating lifespan of 'a full Martian year'. The MERs are already at twice that timespan.

Bill


MSL is being designed to last a full Martian year the same way the MERs were designed to last 90 sols.

Posted by: Tom Tamlyn Jul 20 2007, 09:56 PM

The http://mars.jpl.nasa.gov/msl/technology/tech_power.html describes the RTG power system as "giv[ing] the mission an operating lifespan on Mars' surface of a full Martian year (687 Earth days) or more." (my emphasis) All the page is saying is that the power system will work for a lengthy nominal mission. It's not discussing how much longer than the nominal mission the RTG can operate.

The prose could be a little more clear, but I think that mission designers are understandably wary of making comments that could be interpreted as predictions of exceptionally long lifespans for the equipment. The fact that the RTG will keep working for decades isn't very important unless lots of other systems are still working as well.

TTT

Posted by: elakdawalla Jul 20 2007, 10:26 PM

Phew! Story posted. This was a complex one and done in a bit of a rush so I'd appreciate an email if anyone finds any errors.

http://www.planetary.org/news/2007/0720_The_2007_Martian_Dust_Storm_Crisis_for.html

--Emily

Posted by: Pando Jul 20 2007, 11:24 PM

Thanks Emily, great article,

I'm still in awe looking at the http://www.planetary.org/image/Horizon_Survey_1205B_1235B.jpg image in there... blink.gif ohmy.gif

Posted by: djellison Jul 20 2007, 11:29 PM

The MCS stuff is great as well - really good to see what could be an outreach-challenging instrument get good airtime via TPS.

Doug

Posted by: elakdawalla Jul 21 2007, 12:02 AM

There's a lot more where that came from -- I only got those graphs an hour before I posted, so there's much more in there than I had time to explain. More from MCS next week -- that's the instrument that's REALLY designed to stuyd what's going on with the storm.

--Emily

Posted by: Tom Tamlyn Jul 21 2007, 12:54 AM

Emily,

Wonderful story; it's exactly what I was hoping for as a backgrounder on the storm.

Is MCL still unable to perform vertical profiles?

TTT

Posted by: Norm Hartnett Jul 21 2007, 01:51 AM

QUOTE (elakdawalla @ Jul 20 2007, 05:02 PM) *
There's a lot more where that came from -- I only got those graphs an hour before I posted, so there's much more in there than I had time to explain. More from MCS next week -- that's the instrument that's REALLY designed to stuyd what's going on with the storm.

--Emily


Really excellent article Emily, thanks.

If I might make a request? It would be very nice if you could post a follow up article in a day or two once we get comm back from Oppy that goes into more detail on the on going orbital results as well as Rover status.

BTW You really should get that article to some of the major National/International newspapers. It would make a great Sunday Science article.

Posted by: Aussie Jul 21 2007, 02:03 AM

Emily,
As always, your article provides a clear and concise explanation of the situation. The dimming horizons graphic is outstanding.

Posted by: brellis Jul 21 2007, 03:06 AM

Great work Emily, I always enjoy reading your articles!

Posted by: CosmicRocker Jul 21 2007, 06:44 AM

Yeah, I agree with everyone else. That was really a well done summary, Emily. I'm still hopeful the storm is subsiding, and that the rovers will survive, but if not, we will still learn something...

Posted by: vikingmars Jul 21 2007, 02:16 PM

wink.gif Here is a set of 3 pics (calibrated and all that sort of things...) showing the fading of the local horizon at Gusev starting from sol 1122 to sol 1197 and finally ending at sol 1254.
Enjoy it (on Earth, NOT on Mars) !


 

Posted by: tedstryk Jul 21 2007, 03:47 PM

QUOTE (vikingmars @ Jul 21 2007, 02:16 PM) *
wink.gif Here is a set of 3 pics (calibrated and all that sort of things...) showing the fading of the local horizon at Gusev starting from sol 1122 to sol 1197 and finally ending at sol 1254.
Enjoy it (on Earth, NOT on Mars) !


Where did you get truly raw data to calibrate?

Posted by: Ant103 Jul 21 2007, 04:03 PM

Yes, I have the same question : where?

Posted by: centsworth_II Jul 21 2007, 04:14 PM

QUOTE (OWW @ Jul 20 2007, 03:36 PM) *
"... things working in our favor."

Question: what things? huh.gif

Already mentioned in this thread:

Clean solar panels
Warmer temps
Relatively healthy craft
And I'm guessing the batteries are still fairly well charged since
they just now started severely cutting back on communication.

Posted by: OWW Jul 21 2007, 05:26 PM

From http://www.reuters.com/article/scienceNews/idUSN2035182320070720 :

The rovers have electric heaters to prevent vital core electronics from getting too cold. One concern is that absence of sunlight could make the rovers drain their batteries.
That worst-case scenario is still weeks off at a minimum, Callas added. He said that because it was now Martian summer for the rovers, there was a chance temperatures would not fall low enough to ruin the electronics even if the rovers were starved of power.


Sounds optimistic.

Posted by: WindyT Jul 21 2007, 09:52 PM

Idle question -- please consider me off my rocker, but I'm curious if anyone's anticipating the storm to warm some areas enough for a "water release event" in various crater walls.

Posted by: djellison Jul 21 2007, 10:12 PM

The phase diagram shows that the window for liquid water at these pressures is very small. It's quite likely that these conditions putting both the liquid AND solid phase out of the question for much of the day.

Doug

Posted by: vikingmars Jul 21 2007, 10:31 PM

QUOTE (Ant103 @ Jul 21 2007, 06:03 PM) *
Yes, I have the same question : where?

biggrin.gif Sorry my friends, but the the truth is not elsewhere and -unfortunately- I'm not working with secret "X-files" : the images are data from the Exploratorium and processed (+ rotated and cropped to show the same section of landscape) as usual... Anyway thanks for this kind interest of yours on my modest contribution to this nice "Storm" section... smile.gif

Posted by: nprev Jul 22 2007, 01:23 AM

CBS News radio in Los Angeles picked up the story (pretty doom & gloom... sad.gif ), had an interview with Robert Zubrin...was there a press conference today?

Posted by: Bill Harris Jul 22 2007, 02:25 AM

This may be viewing Mars through rose-colored glasses, but Our Intrepid Explorers have been though several tight situations and they've managed to survive. I'm sure they'll weather this dust event. And if not, it's ben a good ride...

--Bill

Posted by: Stu Jul 22 2007, 06:42 AM

Anyone unfamiliar with Vikingmars's work - or wondering "how he does it" should check out his stunning book "Visions of Mars", which is truly a thing of beauty. If "Roving Mars" is The Book for engineering types, then Olivier's book is The Book for all us romantics and frustrated artists out here. smile.gif

Posted by: Stu Jul 22 2007, 07:49 AM

Been working on this for a while, hope some of you like it... smile.gif

THE STORM

The Sun has almost gone now,
fading from my sight behind
a molasses-murky sky, and Earth’s
post-sunset sapphire spark
is just a distant memory.
I cannot move, and drooling over new Victorian vistas
must await until Sol’s golden glow
warms my frozen heart again for I am cold,
so cold, and feel ten thousand sols old
as I stand here, fearful that the dust I see
fouling the sky above me will fall suddenly,
smothering me, Mars murdering me
with her deadly pillow of particles
pushed down against my face –

But I am not dead yet, and although
I itch insanely, and would scratch myself
to wreckage if I had been built with hands
I shall stand here, sentinel-still, until
the sky begins to clear… or I hear
my stubborn heartbeat start to slow,
and then I’ll know my stay
on Meridiani’s rolling plains is at an end
and you, my faithful friends Out There,
must promise not to mourn for me,
but celebrate my life and all the wondrous sights
we saw together. Never think
of me with sadness, but be glad
we walked this world hand in hand,
cresting wind-carved dunes, swooning
at the sight of sunlight painting
Endurance’s epic walls,
falling to our knees in awe as
Victoria’s rippled floor opened up before us..!

But trust me, while a single warming spark
sputters on inside my shivering heart
I will prevail, and as the dust clouds sail
across my sky I shall just close my eyes
against the wind and bide my time,
for Barsoom gloomiest, darkest day
is still a thing of beauty… And if I am to die
here I will still have lived a life
far longer than was planned in this land
of rock and stone. Meridiani is my home,
and if Victoria is to be my lonely
tomb then there is no view I would rather see,
as I drift into my final, well-earned sleep.

© Stuart Atkinson 2007

Posted by: MichaelT Jul 22 2007, 08:06 AM

QUOTE (centsworth_II @ Jul 21 2007, 04:14 PM) *
Warmer temps


I had a search for some Viking data of the great dust storm in 1977 to find out what happened to temperatures then. I found this interesting page by J.E. Tillman, which contains some interesting figures and links to viking data: http://www-k12.atmos.washington.edu/k12/resources/mars_data-information/temperature_overview.html

It also contains a figure with the temperature at the VL 1 site from the beginning of the dust storm:

(courtesy of NASA/JPL)

I do not know how representative such a temperature record is for a Martian dust storm, but, it shows that the daily average temperature does not increase. Rather, the diurnal temperature range is greatly reduced. he nightly minimum is higher, but, the daily maximum also much lower. That nights are warmer is certainly a good thing. What about the much lower daily maximum, though? Any ideas?

Michael

ps: Nice poem, Stu!

Posted by: djellison Jul 22 2007, 08:22 AM

As long as the rover is internally warm enough, then there shouldn't be any component failures - it doesn't really matter how hot it gets - as long as it's not too hot.

The challenge is this. Is combination of whatever energy they are using inside the WEB plus the 8w of RHU's (two on the rem, 6 on the bettery) enough to put enough heat into the WEB to keep the night min.temp. above whatever temperature would cause a failures?

Given that the use of deep sleep has been a regular thing - and that survival heaters were used only during the very coldest nights with Spirit - and that graph suggests 15-20 degrees warmer minimums - then I don't see it as a problem.

Posted by: vikingmars Jul 22 2007, 08:59 AM

[quote name='MichaelT' date='Jul 22 2007, 10:06 AM' post='95554']
I had a search for some Viking data of the great dust storm in 1977 to find out what happened to temperatures then. .../... I do not know how representative such a temperature record is for a Martian dust storm, but, it shows that the daily average temperature does not increase. Rather, the diurnal temperature range is greatly reduced. he nightly minimum is higher, but, the daily maximum also much lower. That nights are warmer is certainly a good thing. What about the much lower daily maximum, though? Any ideas?
Michael

smile.gif I confirm, Michael :
Here are your figures of temperatures (Celcius) during dust storms measured by VL1 and VL2 :
5:00 AM 2:00 PM
VL1 -83° -69°
VL2 -81° -71°

Yes : the rovers will suffer a lot ! sad.gif
Enjoy (if I may say..) wink.gif

Posted by: Astro0 Jul 22 2007, 12:05 PM

Stu... perfect words as always.
I've been working on a illustration for 'The Storm' and now you've created the words to accompany it.
Brilliant prose. I hope that other UMSF'ers appreciate it as well.

Cheers
Astro0

Posted by: tedstryk Jul 22 2007, 02:22 PM

Don Parker's new shots really show how bad it has gotten.

http://img515.imageshack.us/my.php?image=bdd4bj4.jpg

Posted by: diane Jul 22 2007, 04:33 PM

Playing what-if: What if the batteries go to zero, but the temperature doesn't go low enough to damage the electronics. Would it be possible to restart the rovers when power is available? If power goes to zero one or more times, would that in itself be damaging to the batteries?

Posted by: djellison Jul 22 2007, 04:36 PM

I don't think that's a damaging scenario - Li-Ion's don't have memory issues like some older technologies - but I think the tie in is that a little bit of battery activity is possibly required to keep them warm enough to avoid damage.

Doug

Posted by: Sunspot Jul 22 2007, 04:40 PM

Is the next planned communications session sometime today?

Posted by: djellison Jul 22 2007, 05:41 PM

http://trs-new.jpl.nasa.gov/dspace/handle/2014/39793

Very interesting stuff - well worth reading.

Doug

Posted by: Mark Adler Jul 22 2007, 08:29 PM

QUOTE (diane @ Jul 22 2007, 09:33 AM) *
Playing what-if: What if the batteries go to zero, but the temperature doesn't go low enough to damage the electronics. Would it be possible to restart the rovers when power is available?

Maybe.

The big problem there would be the loss of the mission clock, which of course runs off the batteries. (It's connected directly to the batteries, with no intervening switches.) Upon complete discharge and a subsequent recharging and reboot, the clock would be reset to a known value, but with no relation to the current time. All planned wakeups and communication windows which are specified by the value of that clock would then be lost. You would have to rely on solar array wakeup and and fault mode communication windows to get commands in to the X-band radio to try to set the clock and reboot.

It's never been done, but in theory it should work. It might take several sols, since you don't know when it will wake up, you don't know how graceful the last shutdown was (probably not very), and you don't know what fault mode(s) it might be in. The system wasn't really designed for this -- during development, the loss of the mission clock from a complete battery discharge was an accepted loss of mission failure mode. The probability of such a failure in the first 90 sols was considered very small. Still, there's isn't anything that I'm aware of that would prevent such a recovery.

The Spirit sol 18 reboot cycle was also an accepted loss of mission failure mode, but we had enough back doors to recover from that one anyway.

By the way, it's so dark currently at Meridiani, Opportunity isn't getting enough current from the solar panels at any time during the day to trigger a solar array wakeup. While the batteries can recharge at a low light level, it requires more light than that to wake up the rover sans alarm clock.

QUOTE
If power goes to zero one or more times, would that in itself be damaging to the batteries?

It would degrade the batteries slightly, decreasing their lifetime. You try to keep them above a 40% state of charge to maximize lifetime. (Full discharging doesn't help Li-ion batteries like it does for some other battery chemistries.) However these batteries have been doing so well, I suspect there would be little impact from a few 100% discharges.

Posted by: djellison Jul 22 2007, 09:27 PM

Thanks for the update Mark.

If the circuitry is such that it can charge even without an array wake up - will each sol be, technically, power positive?

Doug

Posted by: diane Jul 23 2007, 12:00 AM

Mark, thanks for a very informative answer!

Posted by: Mark Adler Jul 23 2007, 03:28 PM

QUOTE (djellison @ Jul 22 2007, 02:27 PM) *
If the circuitry is such that it can charge even without an array wake up - will each sol be, technically, power positive?

Yes, if there's enough energy to run the clock, the battery controller board, and whatever heaters want to come on (at the time they want to come on), then that sol will be power positive. Any excess energy will begin to bring the batteries up to charge.

If the mission clock is reset, then we will have to wait until somesol when the solar array current gets to two amps for at least 10 to 15 minutes, at which time there will be a solar array wake-up of the computer. The last peak array currents on Opportunity were around an amp.

One thing I don't know is how gracefully the battery controller board will turn on given a slow rise in bus voltage from the solar panels.

Posted by: djellison Jul 23 2007, 04:21 PM

Ahh - so actually - things are better than I thought they might be. Still a bit crap - but not quite as doom and gloom as I thought.

I'm going to plough through the JPL TRS search again and see if I can't understand and interpret this at a system level a little better - BUT - I think this may be the sort of flow of things as I understand them. I'm still not sure whever the cut-off of deep sleep is though.

Obviously ITAR has both hands firmly around the neck of any detailed info on this stuff - BUT - from here :
http://hobbiton.thisside.net/rovermanual/
specifically here
http://newport.eecs.uci.edu/impacct/d_research/d_presentation/JPL-PACC092600.ppt - very very out of date but I'm sure the figures are still roughly accurate
Suggests the 'battery charger board' ( I assume the battery controller board which you refer to) pulls 200mW - <5Whrs / sol.

Rovers are complicated. smile.gif

Doug

 

Posted by: ElkGroveDan Jul 23 2007, 04:51 PM

QUOTE (Mark Adler @ Jul 23 2007, 07:28 AM) *
One thing I don't know is how gracefully the battery controller board will turn on given a slow rise in bus voltage from the solar panels.


Mark, are these things you can test with the spare vehicles and equipment you have at JPL, so you'll know what to anticipate? Do you have a cold facility?

Posted by: Tom Tamlyn Jul 23 2007, 06:07 PM

Cautious optimism as reported in space.com (italics added)

http://www.space.com/scienceastronomy/070723_rovers_update.html


>Steve Squyres of Cornell University, the lead scientist for the Mars Exploration
>Rovers (MER) project, said that both Spirit and Opportunity are in
>"excellent shape" based on a radio transmission received this morning.
>
>"Both came through the weekend beautifully," Squyres said in a telephone interview.
>"They were both power positive over the weekend, meaning they were generating
>more power than they were consuming."
>
>The amount of sunlight penetrating the dust-choked martian atmosphere has
>increased slightly in recent days, and the batteries of both rovers are fully charged,
>said Michael Meyer, lead scientist for the Mars Explorations Program at NASA
>Headquarters in Washington, D.C.

***

>"At its worst, tau was a little over five [for Opportunity]," Meyers told SPACE.com. "
>It now has dropped down to a little less than four."
>
>The tau value for Spirit, hunkered down half a world away from its twin,
>has dropped slightly and is currently just less than four, Meyers added.

Of course the storm could get worse again, as the article mentions.

TTT

Posted by: jaredGalen Jul 23 2007, 06:20 PM

With a Tau of 5 and <1% of sunlight getting to the surface, how much worse could it get? What would it take to really knock down diffuse lighting worse then it has been and to a truly catastrophic level?

For solar reliant machines, these rovers really are marvels of modern engineering, coming out power positive after what was the worst of the storm to date. A credit to the people watching out for them.

Posted by: antoniseb Jul 23 2007, 08:24 PM

QUOTE (jaredGalen @ Jul 23 2007, 12:20 PM) *
how much worse could it get?

Suppose that the storm ends and the high air-born dust just falls with the wind dying down at the same time. How thick would the layer of dust be on the Rover's solar panels?

Posted by: akuo Jul 23 2007, 08:40 PM

QUOTE (Tom Tamlyn @ Jul 23 2007, 06:07 PM) *
>The amount of sunlight penetrating the dust-choked martian atmosphere has
>increased slightly in recent days, and the batteries of both rovers are fully charged,
>said Michael Meyer, lead scientist for the Mars Explorations Program at NASA
>Headquarters in Washington, D.C.

That's the most promising piece of information IMO :-). If they can keep batteries at full charge after these sort of conditions, it must take weeks of tau 5.5+ to really danger the rovers.

Posted by: djellison Jul 23 2007, 09:19 PM

Extraordinary. People have been asking me 'how long can they hibernate' - and under these sorts of conditions, it would seem the answer is basically however long they need to. The systems design - although never designed to - can handle this beautifully.

Doug

Posted by: helvick Jul 23 2007, 09:26 PM

Superb.

Posted by: mars loon Jul 23 2007, 10:14 PM

MarK, thank you for the fantastic info and insights.

its great to hear that the "line of death" is much lower and a indeed much more complicated than thought just a week ago!

and the rover teams accomplishments even more impressive !

Well, here is a NASA update from today July 23 with a few more details. next com session set for Thursday July 26

NASA Mars Rovers Braving Severe Dust Storms
July 20, 2007

Updated July 23, 2007


NASA's Mars Exploration Rover Opportunity sent signals Monday morning, July 23, indicating its power situation improved slightly during the days when it obeyed commands to refrain from communicating with Earth in order to conserve power.

Dust storms on Mars in recent weeks have darkened skies over both Opportunity and its twin, Spirit. The rovers rely on electricity that their solar panels generate from sunlight. By last week, output from Opportunity's solar panels had dropped by about 80 percent from a month earlier.

Rover controllers at NASA's Jet Propulsion Laboratory, Pasadena, Calif., commanded Opportunity last week to go into a very low-power state and to communicate only once every three days. The rover transmitted a small amount of information today. Next scheduled transmission will be Thursday, July 26, though controllers may command Opportunity to send information on Tuesday, July 24.

Meanwhile, communications from Spirit over the weekend indicated that the sky had cleared slightly at Spirit's location on the other side of Mars from Opportunity.

"The outlook for both Opportunity and Spirit depends on the weather, which makes it unpredictable," said JPL's John Callas, project manager for both rovers. "If the weather holds where it is now or gets better, the rovers will be OK. If it gets worse, the situation becomes more complex.

Posted by: nprev Jul 23 2007, 10:15 PM

The MERs continue to shine as examples of truly superior systems engineering, all right. If I wasn't so far along on my topic already, I'd change my thesis subject to them. Maybe one of my classmates who are still looking for an idea might be interested.

Posted by: belleraphon1 Jul 23 2007, 11:06 PM

Absolutely incredible machines, these little rovers. Blessed with a special genius.
I am in awe..... they are our Martian Voyagers... always striving to phone home........

Thanks Stu for the prose. Thanks Mark for the insight and updates.

Craig

Posted by: tedstryk Jul 24 2007, 01:48 AM

It would be really cool if Spirit (since its situation is a bit better) could take a 3 color panorama right now. It could be heavily binned, since the purpose would be to show the overall scene in the dust storm, not resolve fine details. But whether it was a partial or a 360 degree pan, it would be a really nice addition to the MER collection.

Posted by: CosmicRocker Jul 24 2007, 03:33 AM

I'm tempted to give in to a small sigh of relief, but the last time I did, the storm regained strength. If we do see yet another peak on the graph, I won't be nearly as worried as the last time. It's absolutely amazing that Opportunity was power positive through this last peak. smile.gif

I don't remember anyone posting a link to http://themis.asu.edu/dustmaps/ of the dust storm. I discovered it today while looking for news on the storm.

Posted by: djellison Jul 24 2007, 06:58 AM

Mark's updated the figures a little smile.gif

We're now at the point in the decay where during the last decay - we had another outburst.

Doug

 

Posted by: Stu Jul 24 2007, 07:44 AM

Best news for a long time! smile.gif

Anyone else noticed this "stain" in the centre of Oppy's tracks as seen on the new pancam shots..?



I know she's getting on a bit now, but I hope Oppy hasn't developed any incontinence problems... blink.gif

At least the sky looks a bit lighter tho... smile.gif


Posted by: djellison Jul 24 2007, 07:46 AM

Looks like the removal of a lighter coloured crust rather than any sort of staining to me. Some MI's would help.

The last horizon survey image ( which I think is the one you've posted there ) was actually from 1235, 8 sols ago - and is infact - when calibrated - the darkest slice of this cake
http://marsrovers.jpl.nasa.gov/gallery/press/opportunity/20070720a/Opportunity_horizon_br.jpg


Doug

Posted by: Stu Jul 24 2007, 07:51 AM

Was using the word "stain" v v loosely. Wasn't actually suggesting that Oppy had.. well, you know... wink.gif

The last horizon survey image ( which I think is the one you've posted there ) was actually from 1235, 8 sols ago - and is infact - when calibrated - the darkest slice of this cake

Really? Took it off the latest set of pancams released. Oh. B****r. I'll get me coat.

Posted by: djellison Jul 24 2007, 09:02 AM

Well - I think it is - what's the actual file name of any one of the three files involved? Somewhere out there ( and I can't find it now..grrr) is a website where you drop the file name in and it converts it to the information for you. That - or using MMB - will tell you when the image was taken.

Doug

Posted by: AndyG Jul 24 2007, 09:38 AM

QUOTE (djellison @ Jul 24 2007, 07:58 AM) *
We're now at the point in the decay where during the last decay - we had another outburst.

My bottle's half full, Doug. laugh.gif

The Mariner 9 dust storm took several weeks to clear - given that this storm isn't as intense, I wonder how long we'll have to wait until the high Tau conditions tail off. Any thoughts?

Andy

Posted by: OWW Jul 24 2007, 09:55 AM

http://www.tnni.net/~dustymars/Observing_Mars_6

Since 1971, the year of the "Great Dust Storm of Mars," the ALPO Mars Recorders have suspected that these disturbances came in pairs. We have seen that in 1971 a major dust storm occurred on 213° Ls, followed by a "planet encircling" dust storm on 259° Ls. Again, in 1973 a major storm began on 244° Ls and was followed by a "planet encircling" storm on 300° Ls and [Martin, 1974]. The Viking Lander recorded two "planet encircling" storms on 204° and 268° [Tillman, 1988]

This is only the first big storm this season. At present, it's 282° Ls. And the big 1971 storm began to dissipate by 314° Ls. Still a long way to go... smile.gif

Posted by: imipak Jul 24 2007, 10:26 AM

QUOTE (OWW @ Jul 24 2007, 10:55 AM) *
This is only the first big storm this season. At present, it's 282° Ls. And the big 1971 storm began to dissipate by 314° Ls. Still a long way to go... smile.gif


Almost entirely off-topic: http://www.lyricsmania.com/lyrics/james_dean_bradfield_lyrics_8864/the_great_western_lyrics_29107/still_a_long_way_to_go_lyrics_320075.html - an uncannily appropriate lyric.

It's truly extraordinary that both rovers are fully charged after the last couple of weeks. Unless the dustfall at the end of the storm covers the solar panels, it looks like MERs are virtually immortal - if they can survive this, even a prolonged, full-on global storm might be survivable.

Posted by: AndyG Jul 24 2007, 12:05 PM

Thanks for the info, OWW...

So now the question would be, once this storm's abated, do the Opportunity planners take a dip into Victoria, with the risk of getting caught somewhere less pleasant towards the end of a potential 50-60 day window, or sit still for two months with at least the potential for no more bad weather (is storm #2 chance or certainty?) and the risks that accompany an aging rover?

Andy, glad to not be decision-making.

Posted by: BrianL Jul 24 2007, 12:25 PM

QUOTE (AndyG @ Jul 24 2007, 06:05 AM) *
So now the question would be...

I'm not a MER mission planner, nor do I play one on TV, but I would not hesitate to get in there and get valuable science done as soon as conditions permit. A follow-up storm might or might not happen. I don't see them being that far in that they couldn't quickly retrace their steps and get back out unless a massive storm suddenly took hold right in this area. I haven't seen that kind of bad luck yet on this mission (touch wood).

Brian

Posted by: Edward Schmitz Jul 24 2007, 04:11 PM

Why would being in the crater be worse than being outside?

Posted by: djellison Jul 24 2007, 04:18 PM

Because being flat on the plain you get the maximum indirect illumination of the arrays by the dust. On a slope - that will drop off (which every direction the slope is)

With clear skies and 800 Whrs, it doesn't really matter given that the slope runs down to the East (better power in the morning, but lower power in the evening) but with almost all the power currently coming from the difuse route - you want to be flat as you can.

Doug

Posted by: lyford Jul 24 2007, 06:13 PM

Reading over the http://marsrovers.jpl.nasa.gov/mission/spacecraft_rover_energy.html, I found this chestnut:

QUOTE
Also, by the end of the 90-sol mission, the capability of the solar arrays to generate power will likely be reduced to about 50 watts of power due to anticipated dust coverage on the solar arrays (as seen on Sojourner/Mars Pathfinder), as well as the change in season.

How things have changed from then!
The bestest words I have heard this last week are not http://www.unmannedspaceflight.com/index.php?showtopic=4415&hl=- They are "Power Positive!" *




*Though it does sound like some cheesy self help course or weightlifter diet additive when you say it by itself.

Posted by: fredk Jul 24 2007, 06:15 PM

I expect it wouldn't have amounted to a great loss of power if Oppy had been on the planned ingress route to the white layer. Being inside the crater would mean that the apparent horizon as viewed from the rover would be higher than the true horizon, so less sky would be visible. But the white layer is only 4 metres or so vertically inside the crater. The nearest cliffs to the expected ingress route are on Cabo Verde, about 30 m away (recall that they don't plan to drive near any cliffs!). That means (allowing for the height of the solar panel deck above the ground) that only 6 or 7 degrees of the horizon towards Verde would be obscured. Similarly, because of the tilt of the crater slope, a "sliver" of sky very roughly 15 degrees maximum width at the near rim and tapering to zero width at the far rim would be obscured.

You could imagine working out this way what percentage of sky, or how many steradians, would be obscured at the expected white layer study sites. No doubt an accurate elevation model would help here. I very crudely estimate a fraction 0.13 of the sky would be obscured at the white layer.

But there are more factors than just solid angle obscured. The solar arrays are much less sensitive to sky illumination from near the horizon than from overhead, just because light from near the horizon strikes the arrays at a glancing angle. Thus to estimate the power loss you must multiply that 0.13 fraction by a small geometrical factor, which is going to be something like the sine of the typical altitudes of obscured sky - that works out to another factor or order 1/10. Also, from the latest pancam images the sky appears to grow darker near the horizon. Therefore you get down to the 1% order of magnitude for total loss of power at the white layer.

Of course, if levels are truly critical, then even a couple percent reduction (like from 100 Whrs to 98 Whrs) could conceivably be fatal. Still, this likely wouldn't have been very important. I could see us entering Victoria soon after power levels allow mobility.

Posted by: rogelio Jul 24 2007, 06:28 PM

But, when the storm(s) end, wouldn’t more dust settle on Oppie inside the sheltered crater than on the rim? And wouldn’t there be less wind down there to remove said dust?

Posted by: climber Jul 24 2007, 08:12 PM

QUOTE (fredk @ Jul 24 2007, 08:15 PM) *
That means (allowing for the height of the solar panel deck above the ground) that only 6 or 7 degrees of the horizon towards Verde would be obscured. Similarly, because of the tilt of the crater slope, a "sliver" of sky very roughly 15 degrees maximum width at the near rim and tapering to zero width at the far rim would be obscured.

This is interesting fredk. On a much lighter tone but using your idea, in the absolute, we can also demonstrate that having put solar cells under the solar panels could have brought some energy too! ...and even basicaly having put them anywhere on the rovers.

Posted by: Edward Schmitz Jul 24 2007, 11:22 PM

QUOTE (djellison @ Jul 24 2007, 09:18 AM) *
Because being flat on the plain you get the maximum indirect illumination of the arrays by the dust. On a slope - that will drop off (which every direction the slope is)

With clear skies and 800 Whrs, it doesn't really matter given that the slope runs down to the East (better power in the morning, but lower power in the evening) but with almost all the power currently coming from the difuse route - you want to be flat as you can.

Doug

Does anyone have quantifiable differences?

To the best of my understanding, the difference in power would amount to about 3.5% if it were all diffuse.

Updated: I didn't read Fredk's post prior to this response. It seems consistant with my estimations.

Posted by: edstrick Jul 25 2007, 04:55 AM

Months, not weeks...
The storm started in Aug or Sept 71. When Mariner arrived in November, most of the surface was hidden except for south polar cap and the top of the Tharsis volcanos and Olympus. Craters were visible as bright circular spots due to increased scatter from the deeper dustier atmosphere compared with adjacent higher terrain, as was Valles Marineris. After proving that their pre-planned mappign and observation sequences were near worthless, they replanned repetitive storm observation sequences and mapping tests to see how things were clearing. They finally started systematic mapping of the planet in January 72, starting with the least dusty high southern latitudes and progressively moving northwards.

Posted by: Edward Schmitz Jul 25 2007, 03:54 PM

Are they calling this a global event yet?

Posted by: CosmicRocker Jul 26 2007, 04:33 AM

I haven't heard that term used in public yet, Ed. This storm seems not to have engulfed the entire planet so far. It has, however, encircled the planet.

The http://themis.asu.edu/dustmaps/ has been updated with an atmospheric opacity map for July 22-24. Per the latest map, it appears that opacity has improved somewhat for both rovers. smile.gif But it's not obvious yet that the storm is dying as of Opportunity sols 1243-1244.

Posted by: edstrick Jul 26 2007, 05:47 AM

Big storms used to be called global, but Viking and later data showed that that was not strictly true as polar region dust levels are low enough the surface remains visible. Some papers <late 80's?> called the 1971 greatest-ever storm as truely global, while calling other storms as "globe encirclig"

Most pre-1971 storms were not observed well enough to make a clear distinction, and it's likely storms occured during perehelic solar conjunctions and the long periods when Mars is on the far side of the sun and until CCD imaging and advanced amateurs, was essentially not being observed at all.

The basic fact is that the historical record of storm statistics stinks.

Powered by Invision Power Board (http://www.invisionboard.com)
© Invision Power Services (http://www.invisionpower.com)