[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?

[fredk]

In that Oppy shot looking into Endurance I'd guess the sun is somewhat higher than 10 degrees - local time was only around 4:30pm (the rover may be on a significant slope itself). I'd guess 20 to 25 degrees for the solar elevation.

The sky gradient is a combination of lens vignetting and a real gradient. To see the true sky gradient, look at the MRD image on this page:
http://an.rsl.wustl.edu/mer/merbrowser/pro...FF3352P1214L0M1
This image has been corrected (flat-fielded) for lens vignetting etc. You can see that the opposition surge and sky gradient are reduced, but are still visible.

The direct link to the corrected image is:
http://an.rsl.wustl.edu/mer/merbrowser/pro...RD3352P1214L0M1

[Paul Fjeld]

I'd guess 20 to 25 degrees for the solar elevation.
...
To see the true sky gradient, look at the MRD image on this page:
http://an.rsl.wustl.edu/mer/merbrowser/pro...FF3352P1214L0M1
This image has been corrected (flat-fielded) for lens vignetting etc. You can see that the opposition surge and sky gradient are reduced, but are still visible.

Thanks!

I wonder how much that vignetting would be apparent in color and, more importantly, to the eye. I'm sorry that the MER shot has such a high solar elevation after all. I'd like to guess that the gradient effect is even more pronounced at low sun, but I've never seen any pic from Mars with that, other than the hazcam shot.

Paul

[fredk]

I wonder how much that vignetting would be apparent in color and, more importantly, to the eye.

The vignetting part of the gradient is purely a camera effect - you wouldn't see it by eye. The corrected image I linked to should be close to what the eye would see in terms of sky gradient.