From: baalke@kelvin.jpl.nasa.gov (Ron Baalke)
Subject: Mars Observer Update - 08/18/92
Followup-To: sci.space
News-Software: VAX/VMS VNEWS 1.3-4   
Keywords:  Mars Observer, JPL, KSC
Reply-To: baalke@kelvin.jpl.nasa.gov
Organization: Jet Propulsion Laboratory
Date: Wed, 19 Aug 1992 07:35:12 GMT

Forwarded from Glenn Cunningham, Mars Observer Deputy Project Manager

                          MARS OBSERVER
                 DAILY ACTIVITIES STATUS REPORT
                            FROM THE
      KENNEDY SPACE CENTER/CAPE CANAVERAL AIR FORCE STATION

                      Launch Minus 29 Days

Date of report:     8-18-92        Time of report:     6:00 PM EDT


...And for another day, TOS (Transfer Orbit Stage) continues
their trouble shooting, looking for an elusive fault between their
signal return and chassis that shows the characteristics of a diode.
During their activities last night they disconnected the spacecraft
from the TOS at the connectors at the bolted joint on the payload
adapter (without our permission).  Fortunately this verified that the
spacecraft was not the cause of their problem, but did create a
significant issues test control and reverification of the circuits
(see below).  During the day today, TOS has been trying to get
started on a functional test of their system to verify that, even
though they cannot find the location of the anomaly, the system
still performs properly.  Late in the afternoon, another set of
zener diodes between the signal ground and the structure (such as
was identified in the LINS (Laser Inertial Navigation System)), in
their S-band transmitter, was located, and now is considered to be
the cause.  Testing is underway at this writing to confirm this
hypothesis.  A changeout of the S-band transmitter is being considered.

Encapsulation is now scheduled for tomorrow morning, assuming TOS
finds their problem, verifies their performance, and gets their
management approval before 8 AM.  Encapsulation tomorrow will
maintain the Launch Day Dress Rehearsal (LDDR) on schedule for
August 27-29.  Any further delay in encapsulation impacts the LDDR,
and makes the first day of the launch period problematic.

Because the TOS-to-spacecraft interface was opened, the question of
reverification of these circuits has been assessed.  TOS wanted to
run another mission interface test with the spacecraft which the
spacecraft cannot support because the RLE (Remote Launch Equipment)
is at the launch pad.  We wanted to run the mission test on the
launch pad rather than risk breaking the RLE configuration, but
TOS could not support the high risk of doing this test on the pad.
Therefore, we reached a position with acceptable risk which involves
having TOS run their mission test without the spacecraft, the spacecraft
checks all but TOS discrete signals with its GO/NO-GO test on the pad,
and the TOS discretes will not be specifically verified.  This position
is based on the fact that the signals are redundant, they are split
between two connector which will have all other circuit verified,
and used in a voting circuit which requires that two out of four
signals be present.

The RLE is at the pad being checked out.  After the usual daily
problems with the communications circuits, half of the functions
have been verified at this writing.  The special JPL verification
test of the command and clock waveforms has confirmed good
waveforms on half the critical circuits.  The rest will be
completed tomorrow morning.  The RLE will be returned to the PHSF
(Payload Hazardous Support Facility) for battery charging only if
encapsulation slips to Thursday or later.
     ___    _____     ___
    /_ /|  /____/ \  /_ /|     Ron Baalke         | baalke@kelvin.jpl.nasa.gov
    | | | |  __ \ /| | | |     Jet Propulsion Lab |
 ___| | | | |__) |/  | | |__   M/S 525-3684 Telos | Optimists live longer
/___| | | |  ___/    | |/__ /| Pasadena, CA 91109 | than pessimists.
|_____|/  |_|/       |_____|/                     |