Printable Version of Topic

Posted by: djellison Feb 6 2006, 03:39 PM

I've been looking at the new entries at the PDS for WHR quotes, to compile as good a list of actual quoted Whr values as I can......so if you find one, add it to this thread and I'll update this post with figures....any source as long as it's an actual figure and an actual sol.


B0515 - 418 Whrs
B0522 - 462 Whrs

Posted by: helvick Feb 16 2006, 09:42 PM

These are all the power generation numbers I have from the Rover updates:
http://marsrovers.jpl.nasa.gov/mission/status_spiritAll.html
http://marsrovers.jpl.nasa.gov/mission/status_opportunityAll.html

Most of these are specific references but some are not absolutely specific e.g. for the Spirit Sol 219 to 231 update the power level is quoted as "Power is always a major concern as available energy fluctuates between 300 and 400 watt-hours per sol" so I've taken that somewhat arbitrarily as 300whr on Sol 219 and 400whr on Sol231.

Opportunity
Sol Whr
639 720
633 528
630 496
629 470
628 479
627 593
526 650
524 500
456 650
450 620
339 836
333 630
321 546
312 840
316 730
257 700
250 660
199 610
100 610

Spirit
Sol Whr
575 900
572 875
422 800
421 700
420 600
419 400
418 350
284 400
231 400
219 300
204 288
203 370
80 700

Posted by: helvick Feb 16 2006, 09:59 PM

New Scientist Rover Updates.
All of these are a bit approximate in terms of dates and exact power levels.

http://www.newscientistspace.com/article.ns?id=dn8730
Opportunity
Sol 734 600whr
Spirit
Sol 754 450 whr
Sol 704 550whr

http://www.newscientist.com/article.ns?id=dn6824
Opportunity
~Sol 310 "over 900 whr".
Spirit
~Sol 330 600 whr

http://www.newscientist.com/article.ns?id=mg18424710.400
Opportunity
June 2004(~Sol 126 to Sol 155) "dropped to 500-600 whr"
Mid September 2004 (~Sol 230) 700whr

Posted by: helvick Feb 16 2006, 10:13 PM

Steve Squyres http://athena1.cornell.edu/news/mubss/
Jan 3 2006
Spirit
Sol 711 500whr

August 31 2005
Spirit
Sol 581 956whr

April 17 2005:
Spirit
Sol 457 "Over 800 whr"

And I found this in the April 17 2005 update - "We think that the rovers can't survive at power levels much lower than 280 watt-hours". That's where the minimum power level reference comes from.

Posted by: helvick Feb 16 2006, 11:02 PM

The Planetary Society Rover updates.
There are quite a few power numbers quoted but only a handful are specific.

http://www.planetary.org/news/2005/1130_Mars_Exploration_Rovers_Update_Spirit.html
Opportunity
Sol 638 720 whr

http://www.planetary.org/news/2005/1027_Mars_Exploration_Rovers_Update_As_Mars.html
Spirit
~ Sol 645 "High 700's"
Opportunity
~ Sol 625 "High 600's"

http://www.planetary.org/news/2005/0922_Mars_Exploration_Rovers_Update_Spirit.html
Spirit
~Sol 621 885whr
Opportunity
~ Sol 601 630whr

http://www.planetary.org/news/2005/0728_Spirit_Hikes_to_Husband_Hill_Summit_as.html
Spirit
~Sol 557 600-650 whr
Opportunity
~Sol 537 600-650 whr

http://www.planetary.org/news/2005/0605_Mars_Exploration_Rovers_Update.html
Opportunity
Sol 463 620whr
Sol 476 650whr

http://www.planetary.org/news/2005/0325_Mars_Exploration_Rovers_Update_Spirit.html
Spirit
~Sol 435 860whr
~Sol 421 800whr
Opportunity
~Sol 401 "the 600's"
There is also a note that Spirit hit a minimum of 550 "for a while"

http://www.planetary.org/news/2004/1209_Mars_Exploration_Rovers_Update_Spirit.html
Opportunity
~Sol 310 "800-900 whr"

http://www.planetary.org/news/2004/1022_Mars_Exploration_Rovers_Update_Spirit.html
Spirit
~Sol 176 ~400whr
~Sol 236 - Sol 285 "400 - 500whr"
Opportunity
~Sol 126 - Sol 215 "500 - 600whr"
~Sol 216 - Sol 235 "averaging 660whr"
~Sol 236 - "than 700whr"

http://www.planetary.org/news/2004/0819_Mars_Exploration_Rovers_Update_Spirit.html
Spirit
~Sol 223 400whr
Opportunity
~Sol 202 550-600whr

http://www.planetary.org/news/2004/0603_Mars_Exploration_Rovers_Update_Spirit.html
Opportunity
~Sol 128 ~500whr
Note This mentions that Deep Sleep saves Opportunity ~170 whr per sol.

Posted by: djellison Mar 9 2006, 08:12 PM

Just got word from JB

"Spirit is down to about 360-370 Whr and Opportunity is down to about
540-55 Whr"

Doug

Posted by: Bob Shaw Mar 9 2006, 08:35 PM

Time for a graph. anyone?

Bob Shaw

Posted by: helvick Mar 9 2006, 09:12 PM

Here ya go
Spirit


Power is down significantly compared to my prediction at the last check point. My previous estimate had it at 416whr for Sol 774. At this rate it would drop below 300 whr on Sol 829 and below 280 on Sol 849. If a more hospitable environment isn't ound she would drop to 245whr between sol 923 and 938

Opportunity


Opportunity is also down somewhat - I had anticipated it would be at 571 whr at this point . At this rate the minimume power level looks to be 405whr between Sol 902 and 924.

The lower power levels for both rovers might indicate that dust levels are up (which would be unexpected I think) or it might just be unfavourable orientation.

Posted by: Nirgal Mar 9 2006, 10:03 PM

Opportunity

Opportunity is also down somewhat - I had anticipated it would be at 571 whr at this point . At this rate the minimume power level looks to be 405whr between Sol 902 and 924.

[/quote]

So the Trek to Victoria could become a race against the time. If this trend (dust-induced power loss dropps more rapidly than predicted/expected) then we will hit the "operational limit" in significantly less than 100 Sols.
So in order to rech the Victoria slopes in time we should be really making not much less than 20 meters per Sol of driving *on average* which seems pretty fast IMO

Any guesses about the average meters per day Oppy could realistically make in the terrain towards Victoria ?

And, ehr yes: keep up praying for those cleaning events

Posted by: helvick Mar 9 2006, 10:43 PM

At the moment I still don't think that Opportunity will fall below a level at which it can still drive for at least an hour a day but if it is dust deposition that is causing this rather than orientation or an increase in Tau then who knows.

Depends on the type and density of dunes and we don't really know what's ahead yet. On a good pavement she should be able to cover 20-40m even when power drops to 400whr. Around Sol 320/325 she covered 60-80m on sols when she was generating not much more power than she is now (540-600whr)

Oh yes.

Posted by: alan Jun 23 2006, 04:02 PM

From the laest update

Helvick , does your projection account for Spirits current tilt?

Posted by: helvick Jun 24 2006, 01:27 PM

No. My estimates are based on a horizontal orientation and have never taken tilt into account which is a major flaw that I never got round to fixing. Spirit's current tilt adds around 15% extra power to those numbers so the current estimated value from my last chart of around 270whr would go up to around 310whr which agrees pretty well with the reported value. The minimum values from Sol 923-938 will be around 285whr which is very low but higher than the worst that was seen in the climb up Husband Hill.

Posted by: dilo Jun 24 2006, 02:54 PM

Helvick, is your estimated output for sol 923-938 considering also further dust deposition?
If not, I'm a little worried...

Posted by: helvick Jun 24 2006, 03:01 PM

All of my "projections" include a 0.18% cumulative degradation in performance per sol to account for dust deposition so a minimum of around 285whr/sol give or take a couple of watts should be right unless she goes and falls off that rock.

Posted by: dilo Jun 24 2006, 03:27 PM

thanks!

Posted by: RNeuhaus Jun 24 2006, 08:34 PM

Now, how about is the power level of Oppy. I see that latelly, Oppy is only permited to drive around 30 minutes per sol. However, up to know, Oppy still have not posed to tilt to north facing. I seems that Oppy has enough solar energy to rover for some days. Then , when do you believe that Oppy will not be allowed to traverse further?

Rodolfo

Posted by: dot.dk Jun 24 2006, 08:45 PM

Where do you get that 30 min drive time from? And couldn't the reason be that they could drive for longer, but they don't want to? Unknown terrain etc.

Posted by: helvick Jun 24 2006, 09:38 PM

Opportunity current (Sol 856): ~ 382whr
Minimum: 339whr from Sol 937 to Sol 965.

~280whr is (according to SS) the minimum required for basic survival. So we have around 100whr/sol to play with right now and that will drop to 60 or so at the minimum. The rovers burn about ~100w when driving but there are all the other things that have to be done (enabling the gyros\accelerometers, uplink\downlink relay, taking the end of drive images, Sun\Tau measurements) which probably add up to around 20-30whr. So we've got about an hour's driving capability at most right now and it will be dropping to 30 minutes or so as SH winter insolation hits its minimum.

Posted by: RNeuhaus Jun 25 2006, 01:46 AM

The duration of transverse done by Oppy lately was around 30 minutes according tot he calculations which I have made. The Oppy's average speed is around 3.5 cms/sec, that is about 62.5 meters / 30 minutes. Hence, I deduct that Oppy is taking about 30 minutes of driving knowing that Oppy stops every 45 seconds to perform any navigation analysis related for 15 seconds before to resume again the drive. That is the driving distance would be 30*3/4 a little more than 22 minutes to cover a distance of 46 meters.

On the other hand, I was acquainted by the JPL Marsrovers news that they were planning to drive the Oppy toward VC between 30 minutes to 2 hours depending to the energy reserve level.

Hope I have cleared to your inquiry!

Helvick, Thanks of your input!

Rodolfo

Posted by: alan Jun 30 2006, 11:41 PM

http://marsrovers.nasa.gov/mission/status_spiritAll.html#sol874

No mention of how much power this requires. I wonder how it affects the amount of science that can be done.

Posted by: Bob Shaw Jul 1 2006, 01:09 AM

Alan:

Think of the effect if the heaters *didn't* get turned on: EOM.

Bob Shaw

Posted by: Tom Tamlyn Jul 10 2006, 06:51 AM

>For the first time on either rover, Spirit's battery heaters turned on at
>8:15 a.m. local solar time on Mars on Sol 865 (June 9, 2006).
>The heaters activate automatically when local temperatures drop to
>about minus 19 degrees Celsius (minus 2 degrees Fahrenheit).

In "Roving Mars," SS notes (at p. 341) that Opportunity survived at temperatures as low as -46 C (as measured in Mini-TES) the first time they tested Deep Sleep, in May 2004.

In light of this, I'm confused by the recent status report which suggests that this is the first time either Rover has experienced temperature as low as -19 C. Or is the point that the temperatures had never fallen so law during daytime? Or maybe Mini-TES is colder because it's up in the mast?

TTT (puzzled in NYC)

Posted by: djellison Jul 10 2006, 07:11 AM

There's a difference.

That -49 was the temperature of the lens inside Mini TES.

The -19 is the temperature of the battery.

They're both inside the WEB, but the battery does more work, more of the time, so stays warmer for longer - it's the 'hot spot' of the entire WEB I would imagine.

Doug

Posted by: bigdipper Jul 15 2006, 12:50 PM

From 14 July Spirit Update: sol 897-904 Solar array input down to 280 whrs

Hang in there buddy.

Posted by: helvick Jul 15 2006, 02:23 PM

I've noted http://www.unmannedspaceflight.com/index.php?showtopic=2610&st=465# that spirit appears to be losing power generating capacity at a slightly faster rate than I expected when assuming a constant rate of power loss due to dust of 0.18% per Sol.

This latest reported whr number seems to indicate that we might be seeing the effect of local winds picking up and increasing the rate at which dust is being deposited on the panels but it could also be that Tau is increasing earlier this year than last.

From Sol 811 to Sol 853 panel efficiency decreased by ~0.08% per sol.
From Sol 853 to Sol 877 panel efficiency decreased by ~0.10% per sol.
From Sol 877 to Sol 891 panel efficiency decreased by ~0.33% per sol.
From Sol 892 to Sol 899 panel efficiency decreased by ~0.41% per sol.

If that rate continues then Spirit will be in a very bad way. After mid winter insolation increases at less than 0.4% per Sol and power generation capacity would just continue to decline rather than picking up again as summer rolls in.

Posted by: centsworth_II Jul 15 2006, 03:13 PM

I wonder if the computer trouble that Spirtit had in the first days of its mission, which lead to a near complete discharge of the battery, reduced the battery life.

I also wonder if plans are in the works for an attempt at repositioning Spirit to get a better angle to the sun, or if it has been decided to let Spirit live or die as it sits. The danger of repositioning is that it could unintentionally lead to a worse and perhaps deadly power situation.

Posted by: helvick Jul 15 2006, 03:46 PM

It may have but I think we've established that the Lithion batteries used by the MER's should be good for a few thousand Sols unless temperatures drop so far that they actually get damaged. The couple of weeks of trouble at the start probably didn't do Spirit's any good but I don't think they damaged it either.


Spirit has already been manoeuvred into a position with one wheel perched on a rock giving her a very favourable northerly tilt that has increased the power she generates by about 20%. Without that tilt she would currently be generating only 220-230 whr or so per sol. An ideal tilt could increase the power gain by a further 10% or so but it would be an incredibly risky exercise. I don't think anyone would try it now, if they got it wrong and she ended up horizontal it might be impossible to recover from.

Posted by: centsworth_II Jul 15 2006, 05:13 PM

So it looks like the die is cast. Spirit is in the orientation that she is in. The dust buildup is what it will be. And a cleaning event (frost congealing of dust?) will happen or not.

On the bright side, is a large part of the minimum power requirement for life due to heating needs? Will those needs decrease as spring approaches so that even if power levels continue to decrease, the minimum power requirement for life will also decrease as rising night temperatures reduce heating needs?

Posted by: helvick Jul 15 2006, 09:05 PM

There have been requests (well a request) for an update of my power estimate charts. To better illustrate my comments above I've reworked the presentation a bit in an attempt to illustrate the current power situation. So far I've only sone this for Spirit but I'll post one for Opportunity as soon as I can.

The critically important line is the solid red one. The future estimate (the portion of all of the line to the right of the dashed purple vertical line) is based on the current power level and the solar panel's effective efficiency today extrapolated out using the actual Tau and my own estimate of the dust deposition rate from precisely 1 martian year earlier. The basic conclusion in this is that without any cleaning she's not going anywhere.

So I also made a much more optimistic version that includes the effect of similar cleaning events to those seen last year at the same time as they occured just to see what effect those would have.


Max-Power is the theoretical maximum that the panels could generate at a given point in time given the known Tau values and assuming that the panel is flat and there is no dust on it. It should be accurate to within about 5% or so. This is in Watt hours (left axis)
Est Power is my interpolated estimate of the actual power generated at any given point. As far as the historical data is concerned this line agrees with JPL's published Solar Panel Efficiency chart to within +-1.5% which I'm quite happy with. This is in Watt hours (left axis)
Dust Loss is my own estimate of the actual rate of dust deposition at various points in time. I derived this by testing various values for each period in order to make my estimated power line approach the reported power number for each published power value except in cases where we know there was a cleaning event. This is a percentage per Sol and uses the right axis (it's generally ~0.2% but has peaked over 1% on occassion)
Tau is an average Tau value for each Sol taken from the published Tau charts. Uses the right axis.
Today and Last Year. I put in these two vertical indicator lines for today and 1 martian year ago to give folks some sort of visual guide to put the other chart lines into context.

Posted by: bigdipper Jul 18 2006, 12:15 AM

If I read the dust loss plot correctly the _rate_ of loss is plotted as opposed to the cumulative loss due to dust, right?

Trying to add/subract the curves didnt' quite work. Looking at sols +/-830-851 noticed ~0 dust loss (but not 0 loss due to dust).

BTW: 570+ downloads of the HPC excel zip file means you have more than one adoring fan.

Posted by: helvick Jul 18 2006, 06:40 AM

You're correct - the Dust Loss number is a rate not an absolute value - it's an estimate of the rate of change in efficiency of the power generating system from Sol to Sol. ie the power is reduced by that percentage each Sol.

To take an example period the Dust Loss [Rate] is 0.03 from Sol 853 to 882.
On Sol 855 the relative efficiency of the panels compared to Sol 1 is 53.6106%.
On sol 856 it is 53.5945%.
The Sol 856 number is 99.97% of the Sol 855 number. You don't add the values directly, you reduce them by that percentage so you get an exponential decay type curve eventually rather than a straight line, or would be if it lasted long enough and was constant.

Posted by: Nirgal Jul 19 2006, 09:52 AM

Hi helvick,

do you also have the dust accumulation loss rate estimates for Opportunity ?

(and what's the current WHR generated by Oppy right now (must be around 400 Whr, right ?)

I'm concerned by your observation that even with spring season coming, the negative effect of the dust loss rate seems to "overtake" the positive effect of increasing solar insolation

If for Oppy it's similar to the spirit figures (0.1-0.3 % per Sol) then this could limit the remaining
lifetime to less than 100 Sols ... just barely sufficient to reach Victoria at all and then
leaving not much time for doing the science there
( of course we could hope for future cleaning events but, unfortunately we can not rely on that to actually happen ...)

Posted by: jamescanvin Jul 20 2006, 02:37 AM

Helvick.

One thing that struck me last night. The amount of incident sunlight absorbed by dust on the panels must be quite inclination dependent. (Think of the size of the shadow of a dust grain, or the path length through a thin dust film as the the angle varies) Maybe this is the reason for the power falling off faster than expected?

If this is the case then as we appoach the solstice the rate of change of this effect should decrease and even better, give more power than expected as spring arrives.

Does this make any sense?

James

Posted by: helvick Jul 20 2006, 06:11 AM

Interesting idea - this certainly would make sense for beam insolation. The assumption that I made was that the "loss" in power due to dust could be described by a simple efficiency percentage as that seemed to be what the mission planners had thought. Now that I think about it it doesn't make a lot of sense to think it could be so simple.

I think I need to try to model this to see how it might effect power throughout the day and as the Sun's altitude changes from Sol to Sol.

Diffuse light (which accounts for around 30% of power generated at the moment) is definitely not affected in the same way - by definition it comes from all incident angles after all.

Posted by: Nirgal Jul 20 2006, 10:26 AM

Hi Helvick,

do you also have current dust accumulation loss rate estimates for Opportunity ?

(see also my former posting above)

Posted by: helvick Jul 20 2006, 02:55 PM

I haven't carried out the same exercise for Oppy yet - I'll try and post it later this evening.

Posted by: RJG Jul 20 2006, 09:52 PM

I'd agree that it is not affected in quite the same way -but the effect will also will affect diffuse light. That element of diffuse light arriving vertically will be affected less than the element of the diffuse light arriving obliquely.

I'll leave you to model it!

Rob

Posted by: helvick Jul 21 2006, 08:49 PM

Aargh! True there is an effect and it will change the distribution of light on the panel but I have a gut feeling that it will generally cancel itself out. Reflection will play a fairly significant part in it too. Hmmh, some more thinking is in order.

Anyway quick back of the envelope calculations for the beam case show that for the best case situation (midday sun directly overhead) a 33% physical covering of dust would cause a performance degradation of ~45-50%. Exactly the same amount of dust in mid winter (with a maximum solar elevation around 63deg) would cause a degradation of 70-75%.

However that also assumes completely non reflecting dust grains. If they reflect anything (which they do) then a significant percentage of the reflected light will end up becoming available to the panel which could even increase the efficiency of the panel at low solar angles if the dust was quite reflective. Not a simple task to model well I think.

Interesting. Got to think about this more and do some real digging into last years data to see if I can spot any trends.

Posted by: helvick Jul 21 2006, 10:37 PM

Just found some great news from the folks at JPL - they definitely disagree with my guess that dust deposition rates were high and getting worse. From todays Spirit update

For that to be true the dust deposition rate at the moment would need to be very low (~0.05% per sol). Clearly that's good news.
So to celebrate I've effectively trashed my earlier attempt at the power chart and mapped out a possible version using the above data, a much more friendly dust loss rate from the published table for Spirits panel efficiency for her first year, and including two cleaning events (corresponding to the sol 421 and 520 events).

That would allow for quite a bit of activity (ie like trying to move) from around Sol 1100.

Even without any cleaning events under these conditions she would have enough juice to survive fairly easily and be able to keep up the current programme of long term observation while waiting for a bit of a clean.

Posted by: helvick Jul 22 2006, 12:16 PM

The problem with Opportunity is that there is very little data - the last update I can find that mentions power was the 400whr number at the end of May.
Using the same assumptions as for Spirit above I get the following for Opportunity at the moment. Power has just about hit its lowest level for this winter (~370) and will stay around there for a while (say around Sol 925\930) and then will slowly creep up to ~420 at around Sol 1080 and then begin to decline back to 300 whr as Tau increases with SH Spring\Summer. Any cleaning events will significantly change that of course.

Posted by: Nirgal Jul 22 2006, 06:33 PM

Thanks Helvick !

It's encouraging, that even with your conservative estimate and even without cleaning events,
there seems to be sufficient power for Oppy until at least around Sol 1150

BTW.: I really love those excellent diagrams of yours

Posted by: helvick Jul 30 2006, 06:05 PM

More good news on the power front, this time for Oppy - from todays JPL update:

So Oppy is in very good shape and getting better. The following chart shows that even without any further cleaning Opportunity should have enough power generating capability to last through to next winter.


I think I'm going to break out the Laphroaig and have a wee dram to celebrate.

Spirit hasn't been so lucky (yet) but they have confirmed that her power generating capability is not expected to fall below 275 watt hours which is very good news.

Posted by: Nirgal Jul 30 2006, 06:22 PM

Yippie !!

this is very good news !
Thanks Helick, for the prompt power chart update ...

Posted by: ElkGroveDan Jul 30 2006, 10:04 PM

I see you like to celebrate in style.

Posted by: dilo Jul 30 2006, 10:51 PM

Great news, helvick. I think we definitively need another mission extention, something like another earth year (up to sol 1350). This would allow Opportunity to complete Victoria Crater exploration and, hopefully, Spirit will be able to climb the Mc Cool hill (but probably we need a cleaning event too!).

Posted by: Nirgal Jul 31 2006, 06:56 AM

yes: comleting Victoria exploration and Mc Cool Summit - that would be the absolute dream of the perfect mission !


so let's just pray that the hardware will last long enough ...
<sol 1350 vision>
Oppy is dragging its broken IDD on 3 wheels accross the bottm of Victoria while Spirit finishes a one-eyed McCool Summit Panorama after having creeped to the top at a pace of 2-meters-per day
</sol 1350 vision>

Posted by: helvick Aug 1 2006, 10:37 PM

:-) The Islay single malts are ideal for special events - Laphroaig in particular really is a delightful mix of heaven and hell that I can only ever drink slowly and in small quantities so there's no fear of ending up with a hangover afterwords which is definitely a good thing since a Laphroaig hangover would probably be an awful thing indeed.

Posted by: RNeuhaus Aug 1 2006, 11:07 PM

About Oppy news are very good and what about the news about Spirit. It is matter of crossing fingers or not? Just withstand for few days until after August 8. Will Spirit survive that time?

About Nirgal's comment, how bad will be the both girls, they will end like pirates, limping on the roads.

Rodolfo

Posted by: bigdipper Aug 5 2006, 08:33 PM

From the August 4, 2006 mission status for sols 915-921

"Spirit is collecting about 280 watt-hours of electrical power each sol from the rover's solar array"

http://marsrovers.jpl.nasa.gov/mission/status.html

Posted by: bigdipper Aug 12 2006, 02:54 AM

From the August 11, 2006 mission status for sols 922-928

"Spirit continues to collect about 280 watt-hours of electrical power each sol from the rover's solar array"

http://marsrovers.jpl.nasa.gov/mission/status.html

The winter solstice has passed (Aug 8, 2006).

Posted by: bigdipper Aug 19 2006, 07:23 PM

From the August 18, 2006 mission status for sols 929-932

"Spirit is collecting about 280 watt-hours of electrical power each sol from the rover's solar array"

http://marsrovers.jpl.nasa.gov/mission/status.html

280 going once, 280 going twice, do I hear 300?

Posted by: helvick Aug 19 2006, 10:04 PM

I think she'll be hovering around this number for at least another three weeks unless we get a cleaning event but it is very good to see that the number has not fallen below 280whr at all - that definitely confirms that dust accumulation on the panels remains very low.

Posted by: bigdipper Sep 9 2006, 05:17 PM

Three weeks later... still at 280 whrs.


Even though spirit is not doing much, she's active beyond "wake up, beep okay, go to sleep" so there's still some power margin.

The good news is that following the 8/8 solstice the sun is up a little higher every day. Sun vs dust accumulation, sun wins - right?

I figure spirit will be out and about around the third anniversary of her landing for sure. Hopefully sooner.

Posted by: Jeff7 Sep 10 2006, 03:16 PM

I assume that there's no chance of this, as it hasn't been done yet, but I'll ask anyway:
Couldn't they use the deployment motors to change the angle of some of the panels, namely the rear flap and one of the wing arrays? Or are those motors one-time use things, or incapable of moving in an "undeploy" direction?

Posted by: djellison Sep 10 2006, 04:43 PM

It's technically possible...but to quote Theisinger..

"I would not do that"

Better to have low power than an array stuck in an upright position, and consider the power cables that have experienced almost 1000 100 degreeC swings - they'll be brittle and potentially breakable when performing a stunt like that.

Doug

Posted by: Tom Tamlyn Sep 15 2006, 05:43 PM

According to the http://marsrovers.jpl.nasa.gov/mission/status_spiritAll.html#sol957, Spirit's solar power has finally started to tick upwards, to 287 watt-hours, from a low of 277 on sol 944 (August 29).

TTT

Posted by: helvick Sep 16 2006, 04:31 PM

Nice to see that the power situation is slowly but surely tracking back upwards. I think we can expect a couple of months of this slow but steady rise in power provided we don't have any early storms.

Time for some updated power charts and my predictions for those who want to see when Spirit is likely to be able to make a move from here.
Right now power looks like it will rise to somewhere around 340whr/sol by the time dust becomes an issue again (~Sol 1034). That's plenty of power to remain safe and healthy while staying put but a bad early dust storm could still cause trouble and the risk of one of those rises significantly as we head into the lead into the back end of SH winter at the end of November\start of December. Even if we do have some local storms the overall power situation is unlikely to drop back to dangerously low levels again this winter, at least for any significant length of time.
It is important to point out that these charts include the ~15% benefit from Spirit's current favourable tilt and without that extra boost she will be back in trouble and will remain effectively unable to move anywhere until she gets a good cleaning. My guess is that she will need to be able to generate 400whr/sol under current conditions (with tilt) or around 340 whr/sol (without tilt) before they make a serious attempt at moving any distance. A minor change in orientation is currently on the cards but that is going to be a very delicate manoeuvre as they will want to maintain that tilt power benefit.

Chart without any cleaning events.

Were we to see similar events to last year then the peak power output would rise to around 600whr/sol from around Sol 1090 (end of Jan 2007). That would certainly make a dash for Home Plate very possible. Here's hoping.
Chart with cleaning events as per last year.

Posted by: centsworth_II Sep 16 2006, 07:33 PM

Storm season is also cleaning season. Last season as I recall, the positive effect of cleaning events outweighed the negative impact of dust buildup. I wonder if that would generally be the case or if it was luck and there could just as easily be a season where cleaning events were no match for the dust buildup. I guess all bets would be off in a months-long global dust storm. I hope we go another season without one of those!

Posted by: helvick Sep 17 2006, 10:07 PM

That could be the case but the long term average net deposition rate must be extremely low or else the entire planet would be just dust. The big problem for the rovers is that the very fine stuff sticks to the panels and that requires some event to kick free (either the "clumping" theory and\or high wind gusts). It will certainly be interesting to see if the pattern of cleaning that we've seen repeats this year and thats experimental data that Spirit can gather without doing much at all.


Likewise. A global storm that pushed Tau up into the 3-5 range would drop Spirit's power generating capacity down to below 50 whr/sol. She might be able to sleep through it as night time temperatures could remain relatively high but I suspect that a long storm would be terminal.

Posted by: bigdipper Sep 30 2006, 01:31 PM

"SPIRIT UPDATE: Solar Power Is on the Rise as Spirit 'Follows the Water' - sol 970-976, September 29, 2006:


Solar power levels on Spirit are slowly beginning to rise again following a winter low of 275 watt-hours on Martian day, or sol, 933 (Aug. 18, 2006). One hundred watt-hours is the amount of electricity needed to light one 100-watt bulb for one hour. This week, the rover's power levels rose to about 296 watt-hours."

--latest Spirit Update

When do we roll? 300? 400? I can hardly wait.

Posted by: helvick Oct 1 2006, 11:16 PM

This is higher than I'd expected at this stage. Either the atmospheric dust loading levels have dropped significantly or the recent evidence we've seen of wind gusts in the area have begun to clean her up a bit.

The team have said they will nudge her around clockwise when she hits 300whr/sol but now they will also wait until after conjunction so it will be the start of November I think.

Posted by: RNeuhaus Oct 2 2006, 02:10 AM

The peak of solar conjunction is at October 23. The total duration of conjuntion is about 2-3 weeks. So, the communications between Earth and Mars start to be restricted by October 16, and will end after November 1. You are right that by the 1st week of november, all Martian robots (MER-A,B, MRO, EX, ODY, & MGS) will start to communicate with the Earth.

Rodolfo.

Posted by: edstrick Oct 2 2006, 10:13 AM

Martian and Venusian conjunctions last longest, as the planet's moving along the ecliptic with a speed that's a significant fraction of the Sun's speed. For the outer planets, they crawl along the ecliptic slow enough that their motion doesn't really extend the conjunction period much at all.

Posted by: RNeuhaus Oct 2 2006, 06:59 PM

Interesting view!

In the other words, the Mercury orbit is closer to the solar planar orbit and Neptune's planar orbit is somewhat lower than the inner planets due to the Sun's path direction. The Sun gravity is pulling the rest of planets in somewhat lagging distance. The longer distance, wider is the gap.

Caution , All of these above words are only formulated by logical toughts.

Rodolfo

Posted by: edstrick Oct 3 2006, 08:52 AM

If you had near-earth asteroids in 1.05 and 0.95 AU orbits, IGNORING that the orbits would be unstable after at most a few close approaches to Earth, their synodic periods would be very long, and oppositions and conjunctions would take months.

And of course, NOT ignoring the effects of Earth's gravity.. Objects at 1.02 AU or so, in the Earth-Sun L2 point, are permenently near opposition, while SOHO, at the L1 point, is permanently in conjunction.

Posted by: hendric Oct 6 2006, 04:54 AM

Dumb question, but which end of the link suffers the most from conjunction? Would it be possible to continue uploading software, or downloading pictures, during a conjunction without responses going the other way until the end of conjunction?

Also, what's the "effective radio radius" of the Sun? Visually, it's about 1/2 a degree, but I'm thinking it must be between 5 and 10 degrees, with the effect of Mars moving behind it in the same direction the Sun is from Earth extending the blackout.

Posted by: helvick Oct 13 2006, 09:20 PM

http://marsrovers.jpl.nasa.gov/mission/status_spiritAll.html#sol977

Posted by: edstrick Oct 14 2006, 11:55 AM

The amount of link degradation decreases with decreasing wavelength/increasing frequency.

A big recurring experiment has been solar corona studies, starting with early interplanetary pioneers, probably, then the Vikings and Voyagers, etc. The more wavelengths the more science you can get as the scintillation's different at different wavelengths.

I don't think there's an effective "radius" for the sun at short radio wavelengths, it's just the signal's cruddied up too much. At longer wavelengths.. Probably MHz and especially kHz, you get refraction and scattering and REFLECTION so strong (ionosphere type) that the solar diameter does go up.

Posted by: bigdipper Oct 25 2006, 01:58 AM

SPIRIT sol 982-987 Oct 16 update
"Solar power is currently about 300 watt-hours"

http://marsrovers.jpl.nasa.gov/mission/status_spiritAll.html#sol982

Posted by: helvick Oct 31 2006, 04:15 PM

From the http://www.planetary.org/news/2006/1030_Mars_Exploration_Rovers_Update__New.html. Powers' definitely on the up.

Posted by: helvick Nov 14 2006, 03:07 PM

http://marsrovers.jpl.nasa.gov/mission/status_spiritAll.html#sol1013 puts power at 320 whr/sol.

Posted by: helvick Jan 1 2007, 01:07 AM

A.J.S. Rayl's Dec 31st update on the Rovers has some worrying news for Spirit. Tau has jumped to 0.9 over the past couple of Sols and power has dropped accordingly to 267whr. I think we're about to find out whether she can survive for long when power drops significantly below 280whr/sol.

Posted by: djellison Jan 1 2007, 01:10 AM

Given the way the first martian year and beginning of the second martian year of Tau figures match so well - this big jump was expected....and ouch - it's going to hurt.

Doug

Posted by: helvick Jan 1 2007, 01:23 AM

Yeah the rise in Tau was definitely on the cards - http://www.unmannedspaceflight.com/index.php?act=Attach&type=post&id=7462has the spike predicted as happening around sol 1045 so we got a couple of weeks grace. Hopefully it wont follow the pattern from last year where it stayed above 0.9 most of the time for around 50 sols. On the positive side potential power is rising very rapidly now too.

Posted by: alan Jan 1 2007, 05:09 AM

Helvick, how many sols is your predicted power offset from the previous year? It looks to me that you have it offset by 685 sols. IIRC there are ~670 sols in a martian year.

Posted by: helvick Jan 1 2007, 12:52 PM

You're right Alan - there are http://en.wikipedia.org/wiki/Timekeeping_on_Marsand I seem to have something wrong with my offset - it varies between ~685 and 666 Sols for the items that I am carrying forward from the last martian year (like Tau and dust loss). I'd better go and investigate how that happened. Oops my bad - good catch though.

Posted by: Tesheiner Jan 19 2007, 08:56 PM

Good news for Spirit on the http://marsrovers.jpl.nasa.gov/mission/status.html:

Posted by: alan Apr 1 2007, 03:42 PM

From the Planetary Society's MER update:

Posted by: Tesheiner May 25 2007, 12:05 PM

http://marsrovers.jpl.nasa.gov/mission/status_opportunityAll.html#sol1164

Opportunity's electrical supply returned to levels not seen since the rover first arrived on Mars. Peak electrical current from the rover's solar arrays climbed above 4.0 amps and remained there for most of the week as a result of three recent dust-cleaning events. The last time electrical current reached similar levels was on sol 18 (Feb. 10, 2004)!

Posted by: CosmicRocker May 26 2007, 04:32 AM

That is really great news for Opportunity, but poor Spirit can't seem to catch a breeze.

I wonder why they started providing measurements of current when all previous announcements told us what energy the rover collected per sol. I don't know what the system voltage is, nor how to weight the incident energy distribution over a sol. Can anyone put this into perspective?

If Opportunity was apparently able to serendipitously take advantage of better winds at a different physical location, Spirit may be able to perform the same feat. Do you think Spirit is capable of moving to a location with higher wind speeds, if it needs energy?

Posted by: alan May 26 2007, 04:40 AM

They probably are using current in this case instead of the usual watt-hours so they can compare between sols with different lengths of daylight.

Posted by: dvandorn May 26 2007, 07:15 AM

I know I heard someone somewhere (most likely in the Opportunity subforum) say that the power is up to roughly 800+Wh, which would make our girl as clean as the day she landed.

-the other Doug

Posted by: helvick May 26 2007, 08:07 AM

Adjusted daily surface insolation (accounting for solar position and atmospheric losses) was approximately 16% higher on Sol 1164 versus Sol 18. My best estimate for sol 18 was that it generated 775 watt hours.

At the same time last year (~23 Sols before Midsummer) panel output was about 620 watt hours per sol. It had peaked about 50 sols earlier at ~720watt hours per sol.

If the 800 watt hours number is true then she is very close to the initial power levels on Sol 1 ~820 watt hours. Sol 1170 insolation is around 13% higher than Sol 1.

Posted by: CosmicRocker May 27 2007, 05:19 AM

Thanks, helvick. You are Really amazing. That is great news for the Oppster. She will probably need to duck in and out of shadows after entering Victoria. What do you people think can be done to improve Spirit's dismal condition? I think they would be able to shake some of the dust off.

Posted by: helvick May 27 2007, 10:30 AM

Poor old Spirit will be in serious trouble once we pass mid summer if she doesn't get cleaned. Right now she's at <400 whr compared to the same time last year when she was perched atop Husband Hill and heading past 900whr per sol.

Posted by: centsworth_II May 27 2007, 03:29 PM

A stepped slope to roll down could do it. But what if some critical
connection gets jarred loose? Could end up worse off.

Posted by: alan Jun 19 2007, 04:51 AM

http://marsrovers.jpl.nasa.gov/mission/status_spiritAll.html#sol1219

A 120 Watt-hour increase to 600 Watt-hours would mean that before the cleaning event power was at 480 Watt-hours. that is significantly higher than Helvick's prediction in this post

http://www.unmannedspaceflight.com/index.php?s=&showtopic=2195&view=findpost&p=68095

I wonder why it was higher?

Did we miss a cleaning event? Did dust clumping clear enough of the panels to boost power? Is the atmosphere less dusty than last year?

Edit: thought of another possibility: less dust settling on Spirit than Helvick's model assumes.

Posted by: helvick Jun 19 2007, 08:48 AM

Alan

It would appear that I was quite significantly off in my estimate of Spirit's power levels prior to this. I think you are right about my dust deposition model but I really will have to rebuild the charts correctly to see if that can explain it all. I suspect that the atmosphere\insolation model I'm using (based on a pre pathfinder paper by Geoffry Landis and Joseph Applebaum) is also slightly inaccurate or (much more likely) I've made some errors in it's implementation.

Time to re do rework and recheck it with all of the newer data to see what comes out.

The good news though is that the baseline before cleaning was much higher than I expected so she has a lot more life left than i had feared.

Posted by: helvick Jun 30 2007, 09:55 PM

Quick question for anyone who knows...

Do we have site by site orientation data for the rovers? Specifically I'm looking for x,y,z rotation data for the main rover body. The Analyst notebook has xyz positional data for Spirit and xy data for Opportunity for the first 700 or so sols but I can't find anything that gives any information on the tilt\rotation.

Posted by: slinted Jul 1 2007, 06:10 PM

Helvick,

I think you'll be able to find that information in the PDS tag of any image from a given position. There is a section called ROVER_COORDINATE_SYSTEM which has a tag called ORIGIN_ROTATION_QUATERNION which relates the ROVER_COORDINATE_SYSTEM (level to the rover deck) to the SITE_FRAME. I could be mistaken about this, but I believe that each SITE_FRAME coordinate system is oriented to true north and level, so the ORIGIN_ROTATION_QUATERNION will provide you the rover's tilt and rotation.

http://pds-geosciences.wustl.edu/geodata/mer2-m-pancam-2-edr-sci-v1/mer2pc_0xxx/document/coordinate_systems.pdf and http://pds-geosciences.wustl.edu/geodata/mer2-m-pancam-2-edr-sci-v1/mer2pc_0xxx/document/mer_pppcs_excerpts.pdf have more information.

Posted by: djellison Apr 16 2008, 11:36 AM

http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/40575/1/07-3234.pdf

Awesome WHR graph for Opportunity in there - including the dust storm drop. Before the storm, the previous low for Opportunity had been about 350 on sol 850ish - and the storm took it to 120.whrs.

D

Posted by: jamescanvin Jun 27 2008, 09:51 AM

Lots of juicy power related figures in the latest Midwinter http://marsrovers.jpl.nasa.gov/mission/status_spiritAll.html#sol1574.

Plus as a bonus a breakdown of what is using the power:

MiniTES heater: 55Whr
Battery Heater: 29Whr
Everything else: 140Whr

Posted by: climber Oct 9 2008, 09:16 PM

May be not the right place to ask since it has to deal with gain instead of Whr.
My question is : as the dust accumulates on solar panels, I guess it accumulates on HGA; so, does the dust lower down communication power when settled on the HGA?
Thanks

Posted by: climber Nov 1 2008, 09:52 PM

Another question here.
Doug has explained in the past why the dust cannot be removed from the panel by wind using the TV screen analogy.
Now the situation is getting worse and I think that may be the dust is no longer accumulating on the panels but on the dust (that already touch the panel) instead.
Question is : can this later dust be blown by the wind easier than the one directly on the panels?
In this case we could hope for a kind of maximum accumulation (pending cleaning events) instead of a growing one.

Posted by: Nirgal Nov 15 2008, 04:54 PM

Probably I missed something ... ( couldn't find the reference in one of the posts or status reports yet )

What is the current WHR situation (and trend estimates) for Opportunity ?

(... now that she is on her long way)

Posted by: ElkGroveDan Nov 15 2008, 05:22 PM

Can the IDD reach any portion of the panels? I wonder what would happen if the rat brush were placed just above a spot on the panel and run for some period of time. I understand how thin the ambient air is, but I can't help but wonder if it might create a weak electrostatic vortex above the panel which would draw off some particles.

Posted by: Nirgal Nov 16 2008, 02:22 PM

Interesting Idea: could be worth a try at Earth in the sandbox under simulated Mars conditions ?

Posted by: climber Nov 16 2008, 09:23 PM

Better idea than mine a few months ago where I proposed to brush the accecible part of the panels

Posted by: dilo Nov 25 2008, 10:09 PM

I think this plot of daily Whr for Spirit (green) and Oppy (red) can be useful. Recent drop to 89 Whrs is even more impressive!