[meteorite-list] C/2013 A1, Mars and spacecraft/rover operation

From: Matson, Robert D. <ROBERT.D.MATSON_at_meteoritecentral.com>
Date: Mon, 4 Mar 2013 11:51:16 -0800
Message-ID: <7C640E28081AEE4B952F008D1E913F17071CE0AB_at_0461-its-exmb04.us.saic.com>

Hi Graham/Jeff/All,

> New data puts it so strike likelihood increasing.

>
http://spaceobs.org/en/2013/02/27/new-data-concerning-the-close-approach
-of-comet-c2013-a1-to-mars/

This is a rapidly evolving situation. Pre-recovery observations of
C/2013 A1 were
reported late last week that were made by Pan-STARRS 1 at Haleakala in
early October,
extending the observational arc by an additional two months. The nominal
closest
approach distance that NASA/JPL is now predicting is 53500 km. (The
maximum distance
of closest approach is ~317,000 km, giving an indication of the
uncertainty that
still remains.) While an impact is not yet ruled out, the trend is
moving in that
direction. If the five observations with the highest residuals are
excluded from
the computation, the nominal miss distance increases to 73700 km.

> If not an impact this means the planet will pass through the comet's
coma. Lots
> of dust and gas. Meteor showers at the surface and all the hardware we
have put
> there will be at risk.

I think the rovers on the surface will be fine; the question is how well
the
three (and eventually four) spacecraft orbiting Mars will hold up
passing
through C/2013 A1's coma. Past interplanetary spacecraft have survived
closer encounters with comets (Giotto, STARDUST), but they were designed
for that mission (and nevertheless sustained damage and sensor
failures).
Mars Odyssey, Mars Express and the Mars Reconnaissance Orbiter may not
do
as well. MAVEN doesn't launch until November of December of this year,
but
coincidentally would arrive at Mars less than a month prior to the
comet.

Dr. Chris McKay at NASA-Ames is on the Curiosity team, and in his
opinion
the coma density would not be sufficient to have much effect on any of
the
orbiting spacecraft. But he emphasized that this was just his opinion,
and
it was made at a time when the nominal closest approach was 105,000 km.

Should MRO suffer a failure, Curiosity will lose its fastest link with
earth (2 megabits/second). It would still have a 256 kilobit/sec link
via Odyssey. If both spacecraft should fail, Curiosity can communicate
directly with earth through its X-band transceiver, but only at 32
kbits/s.

--Rob
Received on Mon 04 Mar 2013 02:51:16 PM PST