What happened to the lander portion of Mars Pathfinder? Options

[Guest_Geographer_*]

The large stationary part returned 16,000 images I saw somewhere. With its huge solar panels and presumably batteries, it should have been able to operate longer than the rover. What happened to it?

[djellison]

http://en.wikipedia.org/wiki/Mars_Pathfind..._of_the_mission

The lander and rover performed for much longer and better than expected, but eventually contact with the lander was lost on sol 83. The lander's silver-zinc battery was only capable of being recharged about 40 times, as a consequence after about 40 sols, the battery was not able to keep the lander warm at night. The exact reason for the final failure of the lander is not certain, but it was probably due to an electronics failure due to the very cold night-time temperatures that were experienced in the final weeks of the mission.

The rover was basically better at keeping itself warm, even though it had non-rechargable batteries - and while we don't know how much longer than the lander it worked for - HiRISE imagery certainly suggests that it moved a few metres of its own accord.

Doug

[Littlebit]

[/i]The rover was basically better at keeping itself warm, even though it had non-rechargable batteries - and while we don't know how much longer than the lander it worked for - HiRISE imagery certainly suggests that it moved a few metres of its own accord.

...must ... find ... alkaline...

[edstrick]

My understanding (based on fragmentary discussions I'd read) is that software to deal with total computer powerdown and morning rebooting was in final development but not ready when the batteries died. I *think* they lost clock reference and maybe the vehicle had to estimate time from sun angle or something. But the result was thought to be difficulty in having the high-gain antenna pointed at Earth at known times and getting commands into the vehicle and responses back without that software. The result was that there were spotty indications of communication for a few days, then nothing, more or less. (Plausibly due to further vehicle deteroriation due to thermal cycling)

The rover had isotope heater "buttons" and aerogel (I think) insulation. No power at night, but it didn't freeze it's <deleted's> off!

[MarsEngineer]

Hi Edstrick,

MPF (lander) did have software to wake in the morning from a cold boot (power off). There was a circuit that turned on the main electronics once the sun was high enough to supply current to a special solar cell dedicated to this. As Wikipedia says, once the lander's silver zinc battery stopped being chargeable (after about sol 40 or so - I forgot - Aug '97 sometime) the system had to be shut off (completely) at night.

Commands (sequences) were sent up at low data rate using the low gain antenna "in the blind" sometime after we thought the lander had woken (around 10 ish). I have to say that after a decade I have forgotten how we set the time in this situation, I think it was a pre-set guesstimated value that we placed in non-volitile memory for tomorrow's wake. I remember it being a pain.

One problem with our design was that we did not have heaters that ensured that the electronics stayed warm (Sojourner had RHUs to keep warm but the lander didn't). If we blew the morning's initialization and startup of th day's activities (including downlinking later in the day), nothing bad would happen, but then nothing WOULD happen which means no heat would be dissipated inside our warm electronics box by the computer and the transmitter which meant that we would be heading into a cold night without having gotten warmed up during the day! (We fixed this design flaw on MER.)

More than once that happened in late Aug and early Sept (mostly due to the challenge of timing the uplink) which meant that by the next morning the lander was very very cold (well below its flight allowable temperature). I think that these low temps eventually got us. (It even sort of happened once on my watch - I was flight director a lot that warm Aug.)

I need to save (and remember) some of these stories for a book. Someday.

-Rob Manning

PS Doug pls check your email. I have a question about the MSL FAQ.

[nprev]

Write the book, Rob; I'll buy it! Hell, a lot of grad schools would buy it as a text, for that matter. Wonderful, invaluable lesson in systems engineering from that anecdote alone, and told most cogently & entertainingly; such information needs to be preserved for both satisfaction of curiosity and further study.

[edstrick]

<waves at Rob> That explains a lot. Running on decade old poorly understood memories doesn't help me get facts right, either.