I believe that they had to shut down some heaters (including the Mini TES) during the first winter to stop a negative power budget caused by the defective arm joint heater . The Mini TES survived so the design must have a decent fudge factor.

Hello,

To follow CosmicRocker, this is an animation who show the last month of Themis data about the storm :
Click to view attachment
(I've added Spirit and Oppy's location)

Beautiful work, Ant...clearly illustrates that Oppy got it first & worst.


(OT here, but it appears that we have a bit of a Matt Groening-inspired avatar party going on this thread!)

Another update on Opportunity here . Things may be getting a little worse.
Keep you fingers crossed

That's just a repost of yesterday's press release.

--Emily

I thought it read kind of like a re-hash . But it seemed to have some new stuff....Oh well.
Your Blog is at The Planetary Society is way more interesting and informative.

Thanks Emily.

New sol 1250 Oppy pancams up on exploratorium. I guess this means that today's expected communication session was a success, and Oppy hasn't yet dropped into low power fault mode. I wonder what the array levels are...

Re-reading this quote from John Callas on the fine Planetary Society blog (which I was not checking daily until reading this thread, despite being a member -- an omission I have now corrected) I had a small & rare positive thought:


"...If there is not sufficient energy, Opportunity will stay asleep. Depending on the weather conditions, Opportunity could stay asleep for days, weeks or even months, all the while trying to charge her batteries with whatever available sunlight there might be."

( http://www.planetary.org/blog/article/00001055/ )

So I'm thinking ahead, say, 40 Sols. Suppose the worst happens -- the heaters trip, the batteries discharge and boom, it's lights out, goodnight Vienna, right? Ah but wait... suppose the panels are covered by a thin layer of dust fallout. As luck would have it, this gets puffed off by a passing not-a-dust-devil... the batteries begin to trickle charge once more and a few days later (as the old sailor's song goes...) "Wa-hey, up she rises"

So the question is, how long do you carry on looking for a signal? More to the point, how long do the actual JPL team carry on looking for a signal? Actually, that now starts to look like a rather less positive scenario - Oppy clings to life, bravely recovers, calls home - and is ignored...




[quick edit: argh-confounded-pseudo-tags!]

I think Pathfinder is a good basis on which to guestimate that... several weeks of daily efforts. Then a few weeks of less-regular efforts, and then a occasional, perhaps once a week, efforts for a couple of months.

Doug

Oh no no no no no no no.... I couldn't go through those dark "Earth to Beagle, Beagle come in please..." days again...

(This topic gets the award for 'Most Depressing For A Long Time" I reckon...)

Yep, and already over 41000 hits in less than a month. I guess it's a record, isn't it ?

Hi all

I remember those pathfinder days of watching and waiting, imagining that Sojourner was driving round and round the Sagan memorial station in the hope of getting a signal.
These days of waiting out this storm are bad but not as bad as back then .......yet

Watching and waiting with you lot

Roy

In this case, you'd have to be more active than just looking for a signal. You would likely have to send commands to get the rover to transmit.


How long and how hard you try is directly related to how futile you think your efforts are. In the case of Pathfinder, after a week or two they were pretty convinced it was futile. In the outlined scenario, there is good reason for hope for as long as there is limited light. Once you've had a few weeks with what appears from orbit to be good sunlight, then you'll start thinking futility. Even then, you might figure that you're just waiting for that wind gust to clear off the panels.

The other constraint on how long you try is money. Commanding every day can be made relatively cheap by having the procedure be completely routine. One mission controller could send commands and listen for a beep every sol, or every few sols. One other person on the project could have a small additional duty to generate the Earth times at which to do that and schedule the mission controller shifts and DSN antennas. The project will be funded for about year after the end of mission anyway for data analysis and archiving, so a little commanding every now and then to search for a lost rover would probably be considered worthwhile.

Of course, this is all hypothetical. Naturally the rovers will come out of this storm fully operational. They're tough little buggers.

Mark

Thank you Mark for that upbeat note. As a taxpayer who advocates for continued funding of these kinds of projects that's the attitude I like to hear. You guys and your project is money well spent.

Thanks for the insights, Mark.

A bit of humour on Lemmon's site:Some numbers too. Oppy still at 4.7 (1250), Spirit down to 3.9 (1271).

This is totally OT, but those words are one of my favorite verses from an ancient Moody Blues song. They were particularly poignant to me in these dark times.

My sentiments, exactly. Thanks for noting that.

...and those appear to be pancam Tau measurements, not estimates based on panel output. I'm trying to correlate these numbers to the published Themis images, which we seem to get earlier than the every-three-days Oppy data. I'll go way out on a limb and say Opportunity will see some improvement on sol 1251, but that's as far as I'll guess.

Another bit of humor from the good doctor's site was, "Never planned this to be a long list ... ."

Don't worry.
Be happy.

"They're tough little buggers." Damn tough, in my opinion...

I'm very impressed by the quite well thought-out recovery procedures, both on the ground & aloft; pretty robust systems engineering for a 90-day mission!

Mark, silly question: How much voltage is required to hold the flash memory, and is there a little teeny backup battery dedicated to this function?

Flash memory requires no power at all to retain its contents.

Updated

Really! Good news, thank you...gotta research this. Wondering right now why we even bother with FPGAs, then, unless this is a related technology and/or flash is rad-vulnerable.

Doug, thanks for the update...not great news, but guess it could definitely be worse.

I'm wondering why the turning on of the emergency heaters would be so bad? Is it so that they cannot be otherwise turned on, except automatically when the low temperature limit is reached? Is there a particular reason to run other electronics instead of the heaters, which I would think would be most efficient in warming the WEB?

For high logic element density, SRAM-based FPGA's have advantage over non-volatile FPGA such as anti-fuse. SRAM-based FPGA's are typically configured from a separate flash device so you can power off your board and the FPGA will reconfigure from the flash after power is restored. Over the last few years, lower density FPGA's have been introduced with an integrated flash to store the FPGA configuration. These are typically targeted at replacing larger CPLD's.

For rad-hard, anti-fuse based FPGA's are sometimes or even usually used. The disadvantage is you only get to burn one configuration. You need a new part if you want a new configuration. With SRAM-based FPGA's, you can change the configuration up to 100,000 times by reprogramming the flash.

I remember reading somewhere that the rover had small Uranium heaters installed at critical position in the rover to keep them at an acceptable temperature. Does anyone know what good these heaters can do in these dire straits?

There are 8 of them as I understand it - 6 on the battery, 2 on the REM. They each chuck out abotu 1W of heat. They've been doing so since the day they landed - and - except for decay - will carry on doing so for some time to come. Essentially they're there making a bad situation slightly less bad than it might be. they wont keep an entirely dead rover warm enough for survival - they just shave a bit off the heating requirements.

Here are both HST July observations (July 23 and 27).

Uranium heaters? Pardon me for being ignorant here, but what isotope would that be? U-233, 235 and 238 all have very low specific heat output as I remember.

Plutonium. From this press release:Eight watts over 24 hours gives 192 Whrs per sol. If most of that heat is useful rather than waste, that's actually a very significant addition to the array output these sols!

Yep, that sounds about right. Plutonium-238 dioxide, the same stuff as commonly used in RTGs.

It all comes down to how much heat you need versus how much heat you can afford. Consider the following analogy: If your room temperature in winter is 11 C, and the minimum you can personally tolerate is 13 C, you may be able to reach 13 C by just leaving your computer and CRTs on for longer periods. Switching on a heater will bring the room up to a much more comfortable 18 C, but at a hefty cost.

Continuing your analogy, why not use the heater to bring it up to 13 degrees C if that's all you need? Which is really my question, don't they have control over the heaters except for the emergency situation triggered by the low temperature? I would think using the heaters would be more efficient in heating the WEB than eg. running the processor.

From a thermodynamic point of view all of the means of heating would be the same since all of the energy gets dissipated as heat eventually (assuming we're talking about stuff happning within the WEB at any rate).

Given that, it would seem (to me) to be better to use the electronics systems to heat themselves where possible as the heat in question would be distributed directly through the thing you most want to heat up and you get the benefit of the other work at the same time.

The survival heaters are thermostatically controlled - you can't bring them on until they reach the critical low, and turning them off would require Deep Sleep mode (something that's not possible during the day).

Oh, they do more than just shave a bit off the heating requirements. It's a sobering thought to consider that without the RHUs, the rovers wouldn't even have been able to last 90 Sols due to depleted batteries.

Hey who took our Mars and put this imposter in its place? It looks like a cue ball
That storm is amazing. Although tthe rovers are struggling, I think we are garnering much new information by having 'ground-truth' on this.

I'm avoiding to visit this thread since its beggining, call it a defensive procedure, but I must agree with you, this possiblity of gathering local knowledge about martian storms by the rovers is another jewel to the crown of glory of this mission.

Oh, no doubt about it; this storm may well prove to be the primary engineering/environmental data acquistion triumph of the MERs with respect to future lander mission designs, at least the solar-powered ones.

Of couse, as the dust settles it will be clinically interesting to see if it affects any other systems, particularly moving parts...though I suspect there won't be any effects since the MER team hasn't missed a beat yet with respect to contingency planning & design. (You guys are just unbelievable! )

If there was any doubt that this is a global dust event, then it should be gone now. Both images show an extremely dusty atmosphere; yet, the second one clearly shows that the intensity of the storm has maintained and spread considerably further over the entire planet within 4 or 5 days. There are only a few spots relatively dust free now. And relative is a pretty inaccurate term here...like basically maybe the pole! Yet even the pole seems slightly obscured in the 27 July image.

I wouldn't go that far. It isn't the same face of the planet, and the south polar cap isn't properly aligned with the south pole, so it may simply be closer to the limb.

Yes, amazing resilience, so far anyway!

I think it's interesting that the widely-quoted minimum power requirements of 280-ish Whr is clearly *not* the minimum, and that the engineering team don't seem particularly surprised by that(?) (In this 2004 post by Helvick the 280Whr figure is attributed to Steve Squyres.)

BTW -- this will be old news for the experts here, but I just came across this interesting doc from a JPL "MER Thermal Design workshop" in 2002, which shows the heaters alone as requiring 172 Whr/day (page 22.)

But minimum survival power should depend on environmental conditions, which vary. It'd be greatest for Spirit in the winter, when temperatures are coldest. It'd be considerably less in the summer. And it'd be least of all (fortunately!) during a dust storm, when nighttime temperatures are moderated by all the dust in the atmosphere. So I think that any quoted minimum power requirement (or power draw by the survival heaters) has to be considered in the context of the conditions on Mars at the time.

I'd be interested to know what the temperature of the electronics box would stabalise at at this time of the Mars season with no heaters on at all.


http://www.lanl.gov/news/index.php/fuseact...y/story_id/4763


The radioisotope heater units provide about 200wh of heat /day. In the worst case it may be best to let the electronics boxes just stay cold for a few days if its not too much below -40Deg C. The heating and cooling cycle must surely put more strain on them than if they just cool down once.

Quite a bit of activity planned for the upcoming sol B1254 - even some pancam colour! Got to keep those electronics warm.



P.S. I don't know how long they have been there, or if it has been mentioned here before in my absence, but I noticed some long range planning in the database.



James

Sol 4216! I like the sound of that!

Seriously, there's a new themis map. If I'm oriented correctly, it appears to show considerable clearing over Oppy! However, I've been meaning to ask - am I interpretting these images correctly, that the upper map of the pair that I linked to is an interpolation based on the individual measurements shown in the lower map? If so, the sampling is pretty sparse, which has got to add a lot of uncertainty unless we happen to sample right on top of Oppy.

Woohoo! I guess they have some power to burn thanks to Oppy's latest, probably transient, clearer skies. The storm is still not showing any signs of waning.

fredk: I am sure the upper map is an interpolation of the lower data set. That kind of data interpolation will always be a bit of an art.

This is another take of a sequence already shot on sol 1234. It would be interesting to see the differences.

A few new figures from Mark.

Doug

Phoenix will land on Oppy Sol ~ 1557
MSL will land on Oppy Sol ~ 2350-2400
and Sol 4216 will be by end of july 2015 ...

It looks like the trend is broken at last!

Hope there isn't still latent a longer one.

Berries on the move.



Click to get full res (5.2Mb) from my website. (First update in 6 months!)

James

There is little movement of the blueberries in the undisturbed area. Disturbed blueberries do move considerably. But there is one undisturbed place where something strange is going on. It looks like the soil is pushed up from an underground fissure.
Click to view attachment