From: baalke@kelvin.jpl.nasa.gov (Ron Baalke)
Subject: Mars Observer Update - 09/27/92
Followup-To: sci.space
News-Software: VAX/VMS VNEWS 1.3-4   
Keywords:  Mars Observer, JPL
Reply-To: baalke@kelvin.jpl.nasa.gov
Organization: Jet Propulsion Laboratory
Date: Mon, 28 Sep 1992 03:50:03 GMT

Forwarded from:
PUBLIC INFORMATION OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011

                   MARS OBSERVER STATUS REPORT
                       September 27, 1992

          All systems are operating normally on the Mars Observer
spacecraft on the second day following launch.

          Mars Observer was launched at 1:05 p.m. Eastern
Daylight Time (10:05 a.m. Pacific Daylight Time) on Friday,
September 25, from Cape Canaveral Air Force Station, Florida.
Performance of the Titan III launch vehicle and Transfer Orbit
Stage (TOS) upper-stage booster appear to have been normal,
although telemetry was not received from the TOS during launch.

          Approximately 1 hour, 10 minutes after launch, the
spacecraft executed commands to deploy its solar array and high-
gain antenna in cruise positions.  Ground controllers did not
receive confirmation from microswitches onboard the spacecraft
that the high-gain antenna had latched in its cruise position
until 4:32 p.m. PDT, or about five hours later.  They believe
that the antenna probably deployed most of the way immediately
but did not latch into position until later.

          Other minor anomalies following launch have also been
resolved.  When the sun sensor on the solar array did not acquire
the sun, the spacecraft's fault-protection software switched to a
secondary sun sensor, which acquired the sun and is operating
normally.  Also during the first hours after launch, an unknown
torque on the spacecraft occurred which required action of
gyroscope-like reaction wheels to restabilize the spacecraft, but
this has not reoccurred.

          Also on the first day after launch, a series of star
calibrations failed which caused the spacecraft to switch from
its normal cruise mode, called "array normal spin," to a mode in
which the spacecraft revolves in relation to the sun.  Ground
controllers believe this may have been related to forces
introduced during the high-gain antenna deployment.  On Saturday,
September 26, controllers sent the spacecraft commands to return
to its normal cruise mode.  The spacecraft executed these
commands and has been operating normally since.

          At about 4:35 a.m. PDT today, ground controllers sent
the spacecraft its first regular command load.  Among other
tasks, these instruct Mars Observer to play back data recorded
onboard during the launch phase Friday.  This will help evaluate
performance of the TOS booster.

          The next major activity planned for Mars Observer is
deployment of booms for two of its science instruments, the gamma
ray spectrometer and the magnetometer.  Controllers will transmit
commands for these events on Monday and the deployments will take
place Tuesday.

          As of 12 noon PDT today, Mars Observer is approximately
700,000 kilometers (430,000 miles) from Earth, traveling at
13,000 kilometers per hour (8,060 miles per hour) with respect to
Earth, and 120,000 km/hr (74,400 mph) with respect to the sun.

                              #####
     ___    _____     ___
    /_ /|  /____/ \  /_ /|     Ron Baalke         | baalke@kelvin.jpl.nasa.gov
    | | | |  __ \ /| | | |     Jet Propulsion Lab |
 ___| | | | |__) |/  | | |__   M/S 525-3684 Telos | Quiet people aren't the
/___| | | |  ___/    | |/__ /| Pasadena, CA 91109 | only ones who don't say
|_____|/  |_|/       |_____|/                     | much.

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