Phoenix - spring images, HiRISE views of Phoenix after the long, long winter Options

[Phil Stooke]

Doug just said in another thread that he was looking for Phoenix in the new images and couldn't find it. Well, I love a challenge. So here it is:

Close-up:

(REMOVED - SEE LATER POST)

Context:

(REMOVED - SEE LATER POST)

Note that map-projected HiRISE images at this latitude are in polar stereographic projection, not a cylindrical projection. North is at the left.

You might not believe this, but by blinking layers like Clyde Tombaugh I think I can match numerous points, not just the hardware.

EDIT: I was a bit off. Correct locations are shown below.

Phil

[hendric]

The other thing to think about is that the 18th is the earliest an optimist would expect a reponse. Phoenix stopped transmitting at about the same sun angle, on the way to winter, which means that it's batteries were supplying power and probably extended the time she could send. On the way out of winter, the batteries are going to be dead, and so will not be supplying any extra juice to get her signal out. I'm sure her power management hardware actively controls the battery charging, but I'm not sure how much control the software has over that coming up from a completely dead state, ie the power manager circuit might start trickle charging the battery to raise the voltage well before the CPU comes out of reset. In some cases, such as mobile phones, a charged battery is required for the transmitter to work, since the transmitter uses much more instantaneous power than the wall charger can provide. If you read his description, he does state that the lander waits 19 hours between 2 hour listening windows, for Lazarus mode to cycle the listening window across the whole day because the on-board clock would be reset. For that, the batteries do need a charge. So, my expectation is that the lander will need to wait significantly past the Jan. 18th minimum sol altitude to charge up the batteries enough to last through the night.

[mcaplinger]

Phoenix stopped transmitting at about the same sun angle, on the way to winter, which means that it's batteries were supplying power and probably extended the time she could send.

I'm not convinced of that since the accounts suggest the batteries were dead at wakeup from running heaters overnight. At any rate, the batteries are very likely to be useless from being frozen at zero charge -- http://www.edn.com/blog/1470000147/post/510028451.html -- so I think we will probably not be able to use them. I think PHX can transmit with a dead battery. One could look at when the ODY overflights are relative to when one would expect max power on the panels to figure out what the most likely recovery time would be.

[Deimos]

The 2008 use of "Lazarus mode" started when the batteries fully depleted overnight. If the batteries had retained charge through the night thereafter, the 19 hour cycle would have worked--but the batteries depleted repeatedly, resetting the clock, and making all known wake-ups occur in the mid- to late-morning (worst time for UHF overflights). Any spring mission without batteries would start with the same problem; but once (IF) Earth regains control, one can imagine a sequence keeping it awake through mid-afternoon. There would be no overnight data storage: data would be taken prior to a pass and sent in the afternoon, and anything after the last pass would be forgotten. And a functioning spacecraft might not have functioning instruments--surviving a couple likely failure modes does not imply surviving all. (Not too mention my take on the HiRISE images, especially August, does not lead to optimism.)

Still, best case is that there could be some repetitive imaging and MET data, and that would be quite cool. If it comes back, I'd expect (my guesses only) that an especially close late morning overflight might see the first signal; that it would take effort to get a sequence loaded, but another favorable overflight would do it; that science content for the sequence would follow later, and would be repetitive. While trying to gain control, each sol's odds would be bad--but time would be on our side, when it was against us in 2008. Also, the lander would be generating a huge amount of engineering data as it tries to wake up each sol, browns out, and then repeats many times until power is sufficient. But the data would not accumulate over sols.