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DORIS Electronic Mail   Tue Dec 22 18:00:01 WET 1998    Message Number 0061
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Author: Bernard Bonhoure (CNES/CST)
Subject: DORIS - Topex/Poseidon receiver

An incident was detected on 13 December 1998 14H31 UTC, for the DORIS 
instrument on TOPEX/POSEIDON satellite. Four different recovery sequences
(commands) were sent to the instrument from 13 December to 18 December. The
final recovery procedure included a complete turn-off and a turn-on of the
sensor, but the instrument did not restart properly again. A permanent 
failure in PROM memory is suspected.

So, we had to switch to the redundant side of DORIS on 21 December 18H31 UTC.
The redundant side began to make measurements on 22 December 04H00 UTC on
the DORIS master beacon. The first orbit was processed from only 4 hours of 
and at the very beginning of the USO warm-up, it showed an RMS on velocity
of about 3 mm/s versus an expected value, after a few weeks, of 0.6 mm/s. This
confirms the good health of the redundant side.

The instrument will be set to the programmed measurement mode tonight, 
this is the routine mode.

BONHOURE Bernard (CNES/DSO/ED/AL/MA)


[Mailed From: Pascal Willis <willis@franz.ensg.ign.fr>]