[X] My Assistant

[antoniseb]

Very soon, Mars will appear too close in the sky to the Sun for us to communicate very well to the MERs. Can someone say what the blackout dates will be, and especially when we start communicating again?

[CosmicRocker]

Yes, Diane, we did. Although they were not terribly interesting, it does seem that some data has trickled in. Tonight I went to JPL's solar system simulator and generated views of the sun as seen from Mars (woops, I mean as seen from Earth). I chose a field of view of 5 degrees, and watched Mars as it and Earth chased one another around the Sun.

The attached gif animation displays the Sun at the center of the 5 degree field of view, so there are 2.5 degrees on either side of the center of the Sun as Mars passes by. By October 31st, it would appear to have gone beyond the nominal 2 degrees of elongation officially quoted earlier, and well past the 0.5 degrees noted as communication limits also officially quoted for MRO, as mentioned by Rodolfo. I enjoyed taking out an old tool I haven't used since I had to draw contour maps by hand, my dividers. By Jove, they still work well as a navigation aid. As far as I can tell from the 5 degree simulator images, these simulator images agree reasonably well with the ephemeris numbers posted by Dave in post #15. An added bonus is a glimpse of Venus and the Messenger spacecraft passing through the scene.

It's also apparent that Mars' orbit as seen from Earth only grazes the edge of the Sun, and isn't totally covered by it. So, what is the story regarding the blackout period for the various Mars missions? I am measuring something like a 5 degree elongation for the November 8-10 dates.