Isn't temperature cycling on external hardware (like the Pancams and Navcams) still an issue? As far as I know, Pancam has no survival heater, only a warmup heater for nighttime operations. Surviving 2000 sols' worth of deep temperature cycles is proving to be a little bit of a challenge for our MSL instruments. (Up on the mast we can't get any of that nice RTG waste heat to keep us warm at night.) Maybe the margins for the MER cameras were really large, or maybe our solder joint lifetime models are just way too conservative.

Hi Mike,

Maybe I should have said "dust accumulations on the solar arrays (and motor brush wear) were our PRIMARY “life limiters”." You are right of course. The diurnal temperature cycles also limit life on bonds and solder joints, but in the MER design phase, we figured that dust and brush wear would most likely beat out Arrhenius-like thermal cycling failures (although we had to prove it). At this point I would have to agree that thermal cycling is a looming threat to the rovers.

And yes there are no survival hearter on the Pancam and Navcams. However MER's survival heaters were not intended to help the thermal cycling problem, they were intended to prevent the instrument temperature from going below the flight allowable temperature (or worse, going below the qual temp). They were meant to keep the hardware from breaking under extreme low temperature conditions. The energy needed to run heaters to reduce cycles would likely be a lot higher than for surival heaters.

The issue of thermal cycling is critical for any Mars lander that has to be designed to last on the Mars surface. The hard part is proving that it will last. It is hard enough to "prove" that the design works and survives for 90 sols (with margin), let alone a Mars year. It is a tough one.

Good luck!

-Rob

I just noticed that Spirit hit 900 Sols last night. I know of no one on MER who believed in 10x the design life. No way. I guess we will have to begin to imagine that they could keep on going for some time.

very cool.
Thank to you all for your support and interest in the excitement of Mars Exploration.


-Rob Manning
Ex-MER FS system engineering manager

Just thinking - 83ish Sols for Pathfinder, with Sojourner still going strong could be considered nearly a 12x 'shelf-life exceed'. I desperately hope that MRO might catch some tiny hint of where Sojourner is compared to it's last know location back in 1997.

Thinking of the MSL mast thermal issues - has there been any thought of a solar absorber ( as there was with Beagle 2 ) designed to just warm up during the day and dump it out over night...or is the risk then that during heavy useage, the entire lot ( and there's quite a bit of kit up there I guess ) would get too warm.

Doug

Hi Rob,

Congratulations !!

to you and the whole team and please see that I did make note of Spirit hitting 900 Sols earlier today in the Spirit thread listed below. 10 x design lifetime is such a fantastic milestone that I felt it deserved a special mention.

http://www.unmannedspaceflight.com/index.php?showtopic=2961

ken

Thanks Ken. Very much appreciated (I just noticed your thread). This milestone just creeped up on us.

hi
Doug,
It would be cool to find Sojourner but I fear that it might be too small even for HiRISE. Worth a try though. I have been wrong before.

I do not know much about the absorber that Beagle II used. I know about phase change material that stores the days thermal energy. We tended to find that turning the solar insolation into storable electricuty was more practical for us, but I am sure that for some landers there are good reasons to aviod the complexity of solar arrays, battery chargers, shunts, and batteries.

-Rob

Stu:

There are a lot of great scientific and technical contributors to UMSF. But your lyricism and thought-provoking topic starters are unique. You said it all perfectly, for all of us. Thanks!




john_s:

That states it all so succinctly. My wife appreciates some of the pretty pictures the rovers send back. But she doesn't really "get it". We do.

David

Rob, just want to say how much I appreciate you guys and girls at the JPL bringing the cosmos closer to us. Your work is technical, but the effects are emotional: explosions of joy in the hearts of space geeks around the world.

I remember getting up at 4.30 in the morning in Copenhagen, Denmark, for the EDL of both rovers. Going to the baker around the corner to buy milk and breakfast buns, and then hunkering down in front of the small intermittent video feed from the JPL control room. I shared in your total happiness, and silently praised the dedication and ressourcefulness of a country (the US) and an organisation (NASA/JPL) that would give me such an experience. A highpoint in human exploration, truly expanding the envelope of our knowledge.

I believed back then that the rovers would last about 3,000 sols, and am quite disappointed that they already seem to be reaching the end of their lifetime now. NOT!!!

I am looking forward very much to the Mars Science Laboratory. The skycrane and bridle wil make for a very scary encore of the rovers landings. I hope there'll be two MSL's, but let's see. Couldn't Warren Buffett or Bill Gates cough up some money for a second one? - Write them an email...

What did I expect...

I guess I didn't think about it too much; but if you asked me I would've hoped for about about a year aggregate between the two rovers... I thought going for the hills was very optimistic for Spirit, but she got there, climbed them and came safe down the other side too. I thought Oppy would get to Endurance and finish her time on Mars there. At the time there was mention of a distant crater that was a wildly speculative target requiring ridiculous longevity and survival, dismissed instantly by more practical souls. It was of couse Victoria.

It's been a hell of a hayride. Now the optimism cork is out, we're almost expecting one of the rovers to be still communicating and semi-mobile by the time MSL arrives. However if you asked me now... I might expect another eighteen months, aggregate, between the two rovers. I'm kind of expecting Spirit to make it through at least another few months, and Opportunity to drive around Victoria's rim. And given that we've already had about 5 years between them, that is just incredible performance.

As long as, every day, we can ask "where are we going to go tomorrow, and what are we going to do when we get there," the MER adventure continues.

It's just getting really painful to think of the day when we can no longer ask that question, for either of the girls.

-the other Doug

For me, I was just hoping Sprit could crawl to the base of the hills, and that Opportunity would amble over to Endurance for a look down into the crater. What a freakin' amazing pair of adventures the engineers and scientists on The Team have taken us on. I, and my better half watched each of the EDLs in nearly real time on NASA TV, and I can assure all that we were almost as elated as the crews in the control room when each ended nominally Until the MER missions laid down some serious boot prints on another world, it hadn't ever gotten this good.
I wasn't going to comment in this thread, since all of the good points had already been made, and many quite eloquently. Thanks for capturing a couple of them for reconsideration.

How true. It is really painful to consider the eventual "End of Mission" that we all realize will be upon us one day, and possibly when we may least suspect it. It will be doubly painful, since we have two beloved and intrepid explorers to care about. With some luck, one or both will survive in some capacity until we have a new focus on Mars. Survival until MRO is piping home data is almost assured. If I've got the timeline right, Phoenix will be next, and then MSL. ??

The good news lately is that more are "getting it" every day.

For the entire team, thanks Oerted! I was our privilege.

I doubt that Buffett or Gates have an interest in space exploration, but I am very happy that they have chosen to invest so generously into their Philanthropies. They will make a big difference.

We are working hard to make MSL a success, even with only one rover. It is a challenge; they all are.

Thanks for your support and enthusiasm.

Fellow Mars geek,
Rob

I second David's statement -- thanks, Stu! (BTW - are you the David Finrock of meteorological fame in Texas?! )

My hopes were much more wild than my expectations for the MER campaign, but from my very limited knowledge of the landing sites, I expected Spirit to land in something that resembled a desert flood plain. Rounded boulders, sorted gravels, etc... When the first results came back as everything very basaltic, then I transferred those expectations to Bonneville crater. That crater will show this was a floodplain buried in lava... so after that humble pie, I hoped Spirit would make it to the Columbia Hills and see obvious signs of either a flood or lake. So from that perspective, Spirit has failed to meet my expectations , but the the experience of following this mission in "real" time has surpassed my expectations.

Opportunity I thought would be a mission only a geologist would love: a "boring", endless expanse of sand and small stones. Instead, the evaporite layers were even beyond my expectations at Gusev, since there is evidence of liquid water that persisted over long periods of time, and not a fleeting flood. I cannot imagine any description of Mars geology now being complete without a reference to Meridiani, so from that standpoint, Oppy is a landmark mission.

What did I expect at the beginning...?

Well, I remember the same discussion of prior expectations about the Vikings away back in 1976, when a friend and I concluded that one would work and one would crash like the Russian landers. We were stunned and amazed when Viking turned up 2 for 2, and awe-struck by the first photo of footpad, sand and little pebbles. And the sky was blue for a few days, until NASA re-calibrated against the spacecraft-mounted color chart!

So my advance thoughts on the 2 MERs reflected the initial Viking caution rather than the actual out-turn. I thought Spirit would work OK for a few months, and that Opportunity would be able to send photos but wouldn't get off the lander (or vice versa). Once they were both safely down, I thought Spirit was finsihed when the system crashed in the early days, and thereafter the progress to the rocky rim of Bonneville was so painfully slow that my best hope was to see into the crater. I couldn't imagine reaching the hills.

Once Oppy was down, and we later got those first enticing views out of Eagle from near the Blueberry Patch, I just wanted to see the aeroshell remains and Endurance. I couldn't imagine going further !

The whole thing since has been so extraordinary - geology, astronomy, meteorology and artistic photography. It has absolutely entranced me and I log in every day.

Kenny

I don't know how much fame is involved. But yes, I have been doing the weather for the NBC station in Dallas-Fort Worth for 30 years now.

I had hoped for a career in meteorological research, perhaps in Antarctica, and in my wildest dreams, Mars. (I graduated from Texas A&M about the time of the Viking landings.) But sometimes life throws you a curve, and I have wound up spending my entire career in forecasting for a television station.

David