Subject: [SLR-Mail] No. 1278: TOPEX DORIS system failure
From: Frank Lemoine, NASA GSFC <flemoine@bowie.gsfc.nasa.gov>

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SLR Electronic Mail          2004-11-18 16:30:00 UTC           Message No. 1278 
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Author: Frank Lemoine, NASA GSFC
Subject: TOPEX DORIS system failure
Subject: DORIS and SLR Tracking for TOPEX/Poseidon.
Subject: DORIS and SLR Tracking for TOPEX/Poseidon.

Dear Colleagues,

As announced in  DORISMAIL message 0356, the TOPEX spacecraft
lost its DORIS tracking on November 1, 2004
due to a microprocessor failure on board the satellite. 
The failure occurred in DORIS channel 2, which
was activated in late 1998.  
Steps are underway to see if the DORIS channel 1
can be revived. Attempts to restart DORIS channel 2 were
unsuccessful.  For the short term at least, dense SLR tracking of
TOPEX/Poseidon will be especially important, and we encourage 
stations to track the spacecraft whenever possible.  

TOPEX, a joint mission with NASA and the CNES, has been one
of the  most successful Earth science missions and continues
to return highly valuable data. It&#180;s success is due in no
small part to the dedicated tracking provided by the international
satellite laser ranging community over the past 12 years.   
For nearly two years now, TOPEX/Poseidon
has been flying in an interleaved orbit with JASON-1, which allows
much higher resolution mapping of oceanographic phenomena
on shorter timescales.

The NASA and the CNES thank you for your continued support of this mission.

Kind regards,
Frank Lemoine
Space Geodesy Branch
NASA Goddard Space Flight Center
email: Frank.G.Lemoine@nasa.gov

From: flemoine@bowie.gsfc.nasa.gov 

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