Sol 150+, Time marches on... Options

[Stu]

Sol 150 raws are up so this seems like a good time to start a new thread...

Hang on in there Phoenix...

[peter59]

No, that was just clean up.

Thanks Deimos, I had hope that my assumption is erroneous. I have great hope that now, after the completion of work by RA and TEGA, the Happy Pan will be continued.
Greetings to the whole team. Thank you for everything you have already done.

[01101001]

Yeah, getting grim.

JPL Phoenix Mission News: Phoenix Mission Status Report (October 30)

NASA'S Phoenix Mars Lander, with its solar-electric power shrinking due to shorter daylight hours and a dust storm, did not respond to an orbiter's attempt to communicate with it Wednesday night and Thursday morning.

Mission controllers judge the most likely situation to be that declining power has triggered a pre-set precautionary behavior of waking up for only about two hours per day to listen for an orbiter's hailing signal. If that is the case, the wake-sleep cycling would have begun at an unknown time when batteries became depleted.

"We will be coordinating with the orbiter teams to hail Phoenix as often as feasible to catch the time when it can respond," said Phoenix Project Manager Barry Goldstein at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "If we can reestablish communication, we can begin to get the spacecraft back in condition to resume science. In the best case, if weather cooperates, that would take the better part of a week."
[...]

[bgarlick]

> the wake-sleep cycling would have begun at an unknown time when batteries became depleted.

I find this surprising. As I recall, one of the reasons we lost contact [eventually forever] with Mars Pathfinder was because pathfinder's clock got off and earth had no idea when it was communicating. I believe there are other cases of lost space probes because out of out of sync clocks.

Not loosing track of time seems to be of utmost importance. A digital clock requires such miniscule amounts of power (think of those kid science kits where you power a digital clock by sticking wires into a potato) it seems like they would have had a separate power source for the clock for Phoenix (and all post Pathfinder missions). A single, tiny, buttoncell can power a digital clock for a decade!

If, instead, Phoenix still has a correct time reference, but the mode it has gone into was timed relative to when the 'batteries became depleted' that just seems like a silly software error. No matter when a fault happens, the space craft should always communicate at a deterministic time.

[mcaplinger]

No matter when a fault happens, the space craft should always communicate at a deterministic time.

It can only do this if it has power to do so. And remember that Phoenix can only communicate when an orbiter is going overhead, which only happens four times per day for a few minutes each time. So communicating at a deterministic (Earth) time is not something that makes much sense in this case, without the lander remembering a lot more stuff than it would be a good idea for it to rely on to remember (like exactly when the passes are predicted to occur for a long time into the future.)

If you do things based on an absolute clock, they had better not fail if that clock goes nuts. It's easier to rely on things you can directly observe.