INCIDENT DESCRIPTION AND CORRECTIVE ACTION:

Starting at 129/0116z the CGO spacecraft (S/C) experienced a loss of RF downlink
telemetry when the S/C was initiating a Tracking & Data Satellite System (TDRSS)
Multiple Access (MA) event; several MA events were scheduled which requires the
CGRO S/C 'high gain' antenna and downlinks high data rate science.  Contact with
the S/C was re-established automatically during a scheduled  CGRO S/C Ôomni
antennaÕ (low data rate) event (129/0346z).  When subsequent MA events on the
S/CÕs high gain antenna failed to acquire RF lock, the S/C was rescheduled for
omni antenna events and RF lock was achieved.

The S/C pre-loaded command and ephemeris table loads were checked and verified;
the Absolute Time Command (ATC) counter was updating nominally; Transponder
A & B were operating nominally and verified with the Omni antennas; Nominal
Instrument, Power, and Attitude values were observed.

The CGRO Table 35 ephemeris load was retransmitted (129/0620z), which
reinitializes the on-board table.  The CGRO high gain antenna was manually
commanded for operations successfully at 129/0809:23z; It automatically acquired
the S/C successfully utilizing the high gain antenna during an MA event on
129/0851z.

Note: The original ephemeris load was checked by the Flight Ops Team (FOT) and
Flight Dynamics Facility (FDF); No errors were noted.  Problem under
investigation.


IMPACT ON PROGRAM/PROJECT 
AND SCHEDULED SCIENCE DATA CAPTURE:

All high gain data from 129/0116z Ð 129/0851z lost; Non-recoverable; No S/C
recorders.




CGRO MISSION DIRECTOR SENDS

Robert J. Sodano/GSFC/581/453