Sol 150+, Time marches on... Options

[fredk]

Any idea what the terminal science mode sequence consists of ?

See Emily's blog for details.

[MahFL]

I think we are all suprised at how quick the power situation went downhill.

[helvick]

It was always going to be hard to figure out precisely when Phoenix was going to start to die but we did know that the power loss situation was going to start getting dramatically worse around now. I had estimated that, all thing being equal, she would have been operating at around 50% of initial solar panel power per sol around now and dropping dramatically towards zero. The sudden storm has thrown a wobble into that and I am certain that my estimates of available power tended to overestimate the power from the panels at low solar angles but even so I'm somewhat surprised that she's gone into near death mode this early - I had thought we'd be closer to Sol 200 (and ~25% of initial power levels) before she started to die from loss of power. Clearly though my original estimates were quite a bit out of kilter with reality.

[tedstryk]

The status updates mention that on the day they turned off the heater, they made their last use of TEGA. Was this completed? Also, are there any results from the now-defunct instruments still on board? I would think that downloading these would be a top priority now.

[Deimos]

I'm not aware of any recoverable science data still on board, other than maybe in the MET/Lidar flash. The Biblical Lazarus may have come back with memory intact, but Phoenix comes back thinking it is the day before launch (or some such) and wondering why the touchdown sensors indicate she has landed. And so, Phoenix realizes something has gone very wrong, and begins the Lazarus mode comm strategy.

It looks like the weather situation may have improved, but there is no science and little engineering data to directly confirm that. As Emily said, once there is a good comm session, JPL can regain control. If control is restored, getting into terminal mode science will probably take precedence over anything other than maintaining or improving control. Risks will be avoided due to the already precarious situation. The terminal mode would be very repetitive and would extend the period for which Phoenix returns weather info as long as possible. It is just not obvious Phoenix can handle more than that in Lazarus mode. In the best possible future, the lander's abilities are much diminished, and the ability to respond to conventional science commands is gone, so the commanding strategy is new. So beyond met-related data, expect maybe 30 or so repeated images per sol (sky & frost monitoring) from SSI, and maybe attempts with RAC and maybe attempts with MARDI. And frankly, even that will soon be overly ambitious.

I don't think the situation should be that big a surprise. Before landing, sol 150 was the conventional answer to "how long could the mission last". The power available hit the power needed curve at that time. Weather had been unseasonably favorable, so it looked like Phoenix could go longer before moving to desperation strategies like sacrificing instruments. When the weather turned, it was just to the seasonal pattern that should be in place by sol 150--cloudy and stormy. Sol 200 was never realistic, except maybe as the end of waking up in Lazarus mode for a month, in good circumstances. One factor, by the way, is that it is not just the low power, but also the cold. More power is needed to stay alive; much more was always needed compared to the rovers. Spirit has just set a new record low power level, but still maintained more activity compared to the previous low in winter. Why? It is warmer than in winter. And that is for a tropical location, with RHUs.

[fredk]

A few more details in a new New Scientist article, including

A last attempt to push the soil into the [MECA] cell with the lander's arm on 23 October seems to have failed, says wet chemistry lead scientist Sam Kounaves of Tufts University in Medford, Massachussetts.

[CosmicRocker]

I was looking for something that summarized the mission accomplishments versus the goals, and that NS article was helpful in that regard. Thanks, fredk. It appears as if Phoenix managed to perform many of the tasks that were assigned to it. It seems to have been a success, but who is keeping the scorecard?

[climber]

...but Phoenix comes back thinking it is the day before launch (or some such) and wondering why the touchdown sensors indicate she has landed. And so, Phoenix realizes something has gone very wrong, and begins the Lazarus mode comm strategy.

Forget me for a very innocent question.
Spirit was nearly lost because her flash memory was full of informations gathered before landing that she didn't need anymore at that time.
Now Phoenix is fooled by the touchdown sensors, an information that, in absolute, could have been deleted.
What are the rationales for keeping this on bord? Can "we" build on these exemples to change, in the future, the post landing strategies regarding these issues?

[elakdawalla]

I don't think Deimos meant that anything that Phoenix is doing is the result of some problem with the touchdown sensors. It's just that Phoenix' clock gets reset every time the power goes out, same as the clock on your microwave. "Lazarus mode" is designed to deal with this problem.

--Emily

[Deimos]

Now Phoenix is fooled by the touchdown sensors, an information that, in absolute, could have been deleted. What are the rationales for keeping this on bord?

My understanding is the physical touchdown sensor, not file clutter, is useful to Phoenix right now, to know that Lazarus mode is needed (as opposed to sitting and patiently waiting for launch or some other unproductive thing). This is not part of the problem, but of the solution.

[nprev]

I'm curious now. Assuming that somehow the available energy comes back up to a suitable level for basic operations, how would functionality be restored? Would the flash have to be purged & reloaded (which would presumably require several orbiter passes), or are the basic functions a sort of firmware & therefore immune from power glitches?

[mcaplinger]

...are the basic functions a sort of firmware...

Yes, of course. As far as I know there is no issue at all with the flash, the problem is that the spacecraft clock keeps getting reset to 0. The explanation about the spacecraft thinking it's before launch isn't what I would have expected (most missions have "mission phase bits" that are kept in a nearly-bulletproof type of non-volatile memory) but I don't think any of this has anything to do with the contents of flash.

[climber]

My understanding is the physical touchdown sensor, not file clutter, is useful to Phoenix right now, to know that Lazarus mode is needed (as opposed to sitting and patiently waiting for launch or some other unproductive thing). This is not part of the problem, but of the solution.

Thank you Mark & Emily. Very interesting to see how one (at least me ) could guess the oposite of the reality.