[X] My Assistant

[djellison]

Expect a quiet few sols - http://www.lpl.arizona.edu/~lemmon/mars-tau-b.html
SOL TAU
5097 0.65
5098 0.64
5099 0.67
5100 0.64
5101 0.60
5102 0.60
5103 0.61
5104 1.55
5105 ****
5106 2.12

[Don1]

I did try to estimate the illumination based on the solar panel output, and I was puzzled by why that was coming out so differently from the estimate based on tau. What bothers me about the 22 Watt-hr quoted for the solar panel production is that seems way too much to just run a clock. Are we certain that number is accurate?

Also, if there was a break in the storm the rover might have gotten half an hour of sun which would charge the battery a little. We don't know how much the panels were producing at the time the tau was measured.

On a different topic, the 8 RHUs are providing 192 Watt-hours of energy in the form of heat. If I remember correctly, sunny day production from the panels is about 600 Watt-hours of electricity. So a big chunk of the energy budget of this "solar" powered rover is actually from nuclear sources, even when it is sunny. That surprised me when I worked out the numbers.

[mcaplinger]

What bothers me about the 22 Watt-hr quoted for the solar panel production is that seems way too much to just run a clock. Are we certain that number is accurate?

No, and it was a bit of an off-the-cuff answer, but barring some additional information from the project it's all we have to go on, and it's not implausible given what details of the design we do know. For example, some types of Q-Tech oscillators really do draw 40 mA just for the oscillator, and then for a complete clock there has to be a counter and maybe some other stuff -- the fault protection paper references a "mission clock FPGA".

I also don't fully understand how the scheduling of transmission and reception periods happens if the mission clock is lost. This seemed to introduce a lot of complexity into the attempted recovery process for Spirit. Presumably without the mission clock there's no way for the rover to figure when 11 LST is (in theory it could do with from solar power production but that would vary a lot based on tau, tilt, dust on the panels, etc.); AFAIK this scenario isn't described in the fault protection paper.

[MahFL]

No, and it was a bit of an off-the-cuff answer, but barring some additional information from the project it's all we have to go on, and it's not implausible given what details of the design we do know. For example, some types of Q-Tech oscillators really do draw 40 mA just for the oscillator, and then for a complete clock there has to be a counter and maybe some other stuff -- the fault protection paper references a "mission clock FPGA".

I also don't fully understand how the scheduling of transmission and reception periods happens if the mission clock is lost. This seemed to introduce a lot of complexity into the attempted recovery process for Spirit. Presumably without the mission clock there's no way for the rover to figure when 11 LST is (in theory it could do with from solar power production but that would vary a lot based on tau, tilt, dust on the panels, etc.); AFAIK this scenario isn't described in the fault protection paper.

The rover transmits roughly around midday on Mars, so the orbiters listen then. Once the signal is received they can send commands to the rover, which listens periodically, eventually getting back into sync with Earth.

[mcaplinger]

The rover transmits roughly around midday on Mars...

As noted before, if it was that easy, then how do you explain the need for the "sweep&beep" campaign done for months with Spirit?