Subject: LCROSS Status
From: adamod <[email-masked]>
Date: Sat, 05 Sep 2009 21:22:39 -0500

ATIG Members-

Many of you are already familiar with the Lunar CRater Observation and
Sensing Satellite (LCROSS) mission to impact a permanently shaded "cold
trap" near the Moon's south pole and detect any substantial water deposits
there.

http://www.nasa.gov/mission_pages/LCROSS/main/index.html

Two weeks ago, LCROSS declared a spacecraft emergency after attitude control
malfunctions expended nearly all the spacecraft's propulsion margin while
out of contact with NASA's Deep Space Network (DSN).  This incident occurred
at one of the mission's worst possible intervals, when LCROSS was far south
of the celestial equator and virtually invisible from two of the three DSN
sites (only the site near Canberra, Australia is in the southern
hemisphere).  After some heroics by operations personnel, LCROSS stood down
from emergency status on September 3.

Just before the Labor Day weekend, dedicated JPL personnel (in the FDO/TOPO
tradition) posted an LCROSS ephemeris update to their Horizons website
reflecting tracking into September 3.  Coasting from a terminal Horizons
state 431 sec beforehand, I infer a lunar impact on October 9 at 11:26:05
UTC near 67.9 deg S; 58.5 deg W.  If I coast from a September 4.0 Horizons
state, impact is 11:27:26 UTC near 69.6 deg S; 55.8 deg W.  From these two
coasts, it appears there are no future LCROSS maneuvers in Horizons, but it
won't take much propulsion to hit the target impact point when it's selected
on or about September 10.  I'm frankly amazed the attitude "control"
impulses 2 weeks ago didn't introduce more impact trajectory error.

Attached are a couple trajectory plots from the September 4.0 coast.  Feel
free to share these with colleagues if you wish.

-Dan