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800Whrs+ Staying Up Late ideas
Deimos
post Jul 7 2009, 02:44 PM
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Airglow and discharges have been discussed a few times. One problem with these is that it is generally incumbent on the proponents to do some calculations showing that the cameras could see them. If you take the observation and see nothing, you'd like to at least have an interesting upper limit, as opposed to saying there could have been a full-blown aurora but we're just not that sensitive. That said, we've obviously done speculative and multi-purpose observation, and some airglow & discharge hunting has snuck in. Let's just say I'm not yet aware of any papers underway...

I like time sequences (aka "movies"), as you might guess. Some have been up to 90 minutes long, but if you strung them together at 25 fps you'd get about 1 sec. That's a fundamental issue. Much below 1 bpp, we'd have a movie of compression artifact variation. At full frame, that's 25 Mb for 1 sec of animation. We have lot's of energy available, but downlink has not gone up proportionately. We'd love to use the energy for AM downlinks, but have frequently been unable to. So, 20-70 Mb for a soll is typical. For things like dust devil movies, we need several bpp. so, we've cut the movie down to 1024x256; use low priority for most frames, so they can be deleted if there is nothing (or use the WATCH feature); and limit times we do it to when flash is emptying or at least there's not something big going on later that sol. (Although if anyone can make the sol 1931 anti-sunset twilight movie--p2663--that accidentally looked at home plate--interesting, I might start to buy the argument that any movie would be interesting.)

One part of the data volume argument is that there is no multi-frame compression (eg, MPEG) on the rovers. MSL will have video cameras with video compression.
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climber
post Jul 7 2009, 03:34 PM
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Mark, regarding downlink as well as "20-70 Mb for a sol is typical", now that we're close to sol 2000, could you tell us the total amount of data sent back by Spirit? Opportunity? Is 100 Gb each a good assessment?


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Deimos
post Jul 8 2009, 01:25 AM
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For image data, I've got 125 Gb from Spirit and 129 Gb from Opportunity. That's the lion's share of bits, but MTES is still significant and non-imaging engineering data adds up, too. But I don't have those handy.
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nprev
post Jul 8 2009, 03:33 AM
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QUOTE (Deimos @ Jul 7 2009, 07:44 AM) *
That said, we've obviously done speculative and multi-purpose observation, and some airglow & discharge hunting has snuck in. Let's just say I'm not yet aware of any papers underway...


smile.gif Clearly, I gotta get goofier! Okay, show that in work...


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Astro0
post Jul 8 2009, 04:17 AM
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Deimos said: Although if anyone can make the sol 1931 anti-sunset twilight movie--p2663--that accidentally looked at home plate--interesting, I might start to buy the argument that any movie would be interesting.

I see what you mean. Left eye then right eye animation.
Attached File  Sol1931.wmv ( 513.3K ) Number of downloads: 525

Although, it does look like there were seperate filters used and with stereo pairs and some trickery there could be a nice 3D-synth-colour movie. Any takers?

Of course, we could also add tons of 'lens flares'........hey it worked for JJ Abrams on Star Trek wink.gif
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Stu
post Jul 8 2009, 05:46 AM
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QUOTE (Astro0 @ Jul 8 2009, 05:17 AM) *
Of course, we could also add tons of 'lens flares'........hey it worked for JJ Abrams on Star Trek wink.gif


Well, you can never have too many lens flares... laugh.gif


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CosmicRocker
post Jul 14 2009, 06:06 AM
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I see superres imagery coming down. Who'd have thunk it? We really should have been able to come up with a fat burner like that, or did I miss someone making that suggestion?


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RobertEB
post Oct 2 2009, 02:01 PM
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I am betting the dust devils create static discharges. I seem to recall there was some evidence of this.

It would be neat to capture a night dust devil giving of static discharges. Would it look like lightning? Could spirit see such a thing?


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ElkGroveDan
post Oct 2 2009, 02:22 PM
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....more importantly, do dust devils even blow at night? I think not. The earthly analogs are created by rising air caused by the sun heating the ground all day. In the American Southwest you can even pinpoint a time window a couple of hours before sunset (depending on the time of year). I suspect there is a similar afternoon time range on Mars for the ones we have observed.


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Deimos
post Oct 2 2009, 03:33 PM
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Yes, the Sun plays a big role in dust devils. Orbiter images have shown that globally, dust devil season fallows the sub-Solar latitude around. Dust devils are seen far from those latitudes, for instance in the far northern summer. But there, the Sun never sets; and at least the Phoenix-observed dust devils were much weaker (looking) than their MER counterparts. Back at the Spirit site, dust devils seem confined to 10 am - 4 pm even in the height of summer--and even when trying to control for the observation bias that responds to the same conditions that favor dust devils (solar powered, best to operate when it is warm enough to not need heaters). I imagine the diurnal effect to be quite important, since you need a big temperature gradient just above the ground to get dust devils from a process anything like on Earth. And for the other side of the coin, mini-TES and all models have shown the boundary layer to be super-stable at night.

There were attempts to look for lightning in some night images. They were hampered by a lack of good predictions--could Pancam even see lightning? So, a non-detection is meaningless. The best idea I've heard for seeing it is looking down at the opening for Ma-adim Valles, relying on cooling + gravity to produce winds that stir things up in the jumbled up terrain. Doesn't work now, but there were times...
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mwolff
post Oct 2 2009, 03:58 PM
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QUOTE (Deimos @ Oct 2 2009, 09:33 AM) *
There were attempts to look for lightning in some night images. They were hampered by a lack of good predictions--could Pancam even see lightning? So, a non-detection is meaningless. The best idea I've heard for seeing it is looking down at the opening for Ma-adim Valles, relying on cooling + gravity to produce winds that stir things up in the jumbled up terrain. Doesn't work now, but there were times...


For people interested in lightening from charge exchange in dust events, there is also the possibility of imaging on the nightside by MARCI. However, using the numbers provided by researchers in such things (like John Clarke and collaborators), one was not able to construct a convincing argument for detectability given the large pixel footprints (~1km for visible bands; 8km for UV bands). MARCI does take a set of "dark" images for instrument calibration purposes once a month (or so).

On the issue of the boundary layer, one can actually see the growth of the convective boundary during the morning hours through the point at which it becomes higher than the useful vertical range of the Mini-TES temperature profiles, ~3 km. This point typically occurs by late morning...
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RobertEB
post Oct 2 2009, 05:03 PM
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QUOTE (ElkGroveDan @ Oct 2 2009, 09:22 AM) *
....more importantly, do dust devils even blow at night?


Didn't Spirit have a cleaning event at night?


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Deimos
post Oct 2 2009, 06:35 PM
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And that's good evidence 'cleaning event' does not equal 'dust devil'. You might be able to find just a little discussion of that in the archives. Sitting on a ridge with straight line winds vibrating the panels, cleaning can happen. Hey, here in Texas, I've seen straight line winds that left a damage pattern I'd have thought was a small tornado. Back to Gusev, it is very windy there, day and night, and the winds don't need to go in circles to do interesting things. That could include lightning for all I know, but there is little evidence there's an observable effect.
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