[X] My Assistant

[jmknapp]

Here's a chart showing the elevation of the sun at noon and midnight at the Phoenix lander site for the next year or so:



During one of the press conferences it was mentioned that later this year the situation goes "energy negative" and it's lights out for the lander. What are the odds it could wake up next year when the sun returns? Also, when the sun is only up for a small portion of the day, is it possible to put the lander to sleep and just wake it up for brief periods to use whatever battery power it can get?

[helvick]

Another attempt at estimating the power generated by the solar panels. Mike's links clarified the cell efficiency and confirmed that the panel area is 4.2M^2 so it now appears that Phoenix started off generating almost 3.5 kWatt Hours per Sol. The only major variable I'm not accounting for is the conversion efficiency of the power management system which I'm assuming is 80% but that is just a guess.

I dropped in a variant of jmknapps solar elevation chart in aswell - I thought it was a nice way to see the link between the sun's change in elevation and the drop off in power.

Temperature would be a neat component to add now - anyone know of an easy way to approximate\estimate the change in surface temperature given that I have the overall rate of change in insolation? I'm having some trouble getting my head around thermal inertia so any pointers would be welcome.

[JRehling]

Temperature would be a neat component to add now - anyone know of an easy way to approximate\estimate the change in surface temperature given that I have the overall rate of change in insolation? I'm having some trouble getting my head around thermal inertia so any pointers would be welcome.

TES provided some "ground truthing" as did the Vikings and Pathfinder. Roughly speaking, you can assume a phase shift between insolation and temperature, and from Pathfinder, it looks like it's about 3 hours during daylight and 10 hours during the night.

A key factor is: Which temperature do we care about? Pathfinder showed a difference based upon very slight difference in altitude. We probably don't care if the footpads are at absolute zero but rather about the instrument deck, and with Pathfinder, the difference was small at night but about 6C in the afternoon. The actual instruments may experience a nanoclimate based upon the reflectance of the craft (as opposed to the Pathfinder sensors).

Basically, I think TES will hand you the answers. It was scanning a full line of longitude every day. This data ought to already be on the books. Pathfinder can let you map surface temperatures onto "1 meter" temperatures.

[Paul Fjeld]

(A Newbie's first post.. yay)

I'm doing a painting of Phoenix on the surface at midnight - the view will be from the Northwest looking Southeast, so a good bit of it will be looking nearly down-sun.

I was really hoping that we would have gotten the midnight "Holy Cow!" shot by now so there would be something to get a sense of what low sun, down-sun looks like on Mars. I have trolled the MER pancam shots but haven't found anything relevant yet, nor have I found that one picture I've seen (probably from a Haz Cam?) with the shadow of the rover extending far out in front. Is there a group that is interested in the low-sun/sunrise look of the surface? I have seen some cool stuff of what the sun looks like rising (from Viking as well as MER) but nothing looking the other way.

The sun elevation graph here is really helpful, which is why I'm posting to this thread. (This whole enterprise (UMSF) is incredibly useful and interesting!). I'll post a pic of my work when it is done if that's appropriate.

Thanks!

Paul

[fredk]

... nor have I found that one picture I've seen (probably from a Haz Cam?) with the shadow of the rover extending far out in front.

You may be thinking of this famous shot at Endurance:
http://marsrovers.jpl.nasa.gov/gallery/all...52P1214L0M1.JPG
There was also a similar shot from just inside Vicoria:
http://marsrovers.jpl.nasa.gov/gallery/all...00P1156L0M1.JPG
I can't think of any more looking-away-from-the-low-sun shots at the moment...

I'd love to see your result when it's done...