[X] My Assistant

[fredk]

Spirit shot the night sky again on sol 632, but this time no sign of Phobos or Deimos.

This shot shows Orion. It's upside-down, for northern-hemisphere earthlings at least, but more fascinating is that the star trail direction differs markedly from what you see (anywhere!) on Earth, since Earth's and Mars' axes are well from parallel. It really is jarring to see, if you've ever shot star trails of Orion before!

This shot shows a patch of Gemini, though it's harder to recognize. That's Castor, brightest star along the bottom edge, halfway from centre to right edge. Pollux is just out of frame.

Any ideas what the goal is here, if not just to drain off some excess power?

Would it be feasible to do a real circumpolar-style star shot, showing arcs around an alien celestial pole? For spirit, it'd be Mars' south celestial pole, 15 or so degrees above the southern horizon. A navcam shot could be quite dramatic, with the ghostly outline of McCool/Ramon hills and the south rim of Gusev underneath the alien startrails.

I guess time is the problem - you'd need several minutes exposure at least to show arcs. But perhaps a series of 30 second shots, which could easily be combined digitally? Wishful thinking, perhaps, but then again if there's extra power to drain...

[Bill Harris]

Does anyone know if the navcams are unfiltered, like L1? What is the focal ratio for the navcams?

Here is an overview of the Rover instruments from the Cornell site:

http://athena.cornell.edu/the_mission/instruments.html

--Bill

[fredk]

Here is an overview of the Rover instruments from the Cornell site:

http://athena.cornell.edu/the_mission/instruments.html

--Bill

Thanks for the link, but no info on navcam there, which I guess is not considered an "instrument". I've had no luck googling.

[Tom Tamlyn]

There are a number of scholarly papers discussing the Rover instruments and engineering design, including the papers published in Journal of Geophysical Research special section "Mars Exploration Rover Mission and Landing Sites," vol. 108, no. 12, 2003. See http://anserver1.eprsl.wustl.edu/anteam/mera/mer_jgrref.htm for a table of contents for that issue.

The article you're looking for is probably Maki, J. N., et al., Mars Exploration Rover Engineering Cameras, J. Geophys. Res., 108(E12), 8071, doi:10.1029/2003JE002077, 2003. The abstract is [/URL]here. You can download the article from AGU for $9.00.

I've had the issue in my hand; I can't remember where, but it was probably in the Astronomy Dep't library at Columbia (I live nearby).

At one point in early 2004 I was able to track down quite a few of those pre-landing papers on the web for free, but I didn't save them all, and the ones I have are scattered around. (I'll check for the Maki paper.) The best single source was the syllabus page for a course in planetary geology taught at ASU by Professor Greeley, but that link is dead.

[google, google]

Look at this. It's a page with a live link to a 2001 paper on the engineering cameras.

[google, google]

Eureka! I found a live link to the Maki paper on Michael Lyle's Mars Rover Imagery page. http://www.lyle.org/~markoff/methods.html The same page also has a live link to the lead article from the December 11 special issue, Squyres, S. W., et al., Athena Mars rover science investigation, J. Geophys. Res., 108(E12), 8062, doi:10.1029/2003JE002121, 2003, and other interesting material.

Cheers,

TTT

Thanks for the link, but no info on navcam there, which I guess is not considered an "instrument".  I've had no luck googling.

[fredk]

Eureka!  I found a live link to the Maki paper on Michael Lyle's Mars Rover Imagery page.  http://www.lyle.org/~markoff/methods.html  The same page also has a live link to the lead article from the December 11 special issue, Squyres, S. W., et al., Athena Mars rover science investigation, J. Geophys. Res., 108(E12), 8062, doi:10.1029/2003JE002121, 2003, and other interesting material.

Cheers,

TTT

Thanks for the link! That paper indicates that in addition to the colour filters, the navcams use a 1.3 neutral density filter, which cuts the overall intensity by over 4 stops. This is fine for daytime imaging, but makes for a very slow astro-cam, as the sol 632 navcam shots show.

It seems that L1 pancam is our best shot, and we'll have to ID meteors based on trail length, brightness, and perhaps intensity profile along trail.