ARRL Satellite Bulletin ARLS002 (2001)

ARLS002 AO-40 Could Be Leaking

QST de W1AW  
Space Bulletin 002  ARLS002
From ARRL Headquarters  
Newington, CT  January 5, 2001
To all radio amateurs

ARLS002 AO-40 Could Be Leaking

AO-40 team member Peter Guelzow, DB2OS, says a small leak on AO-40
could account for the higher spin rate ground controllers have
noticed since the satellite resumed telemetry transmissions on
Christmas Day. Guelzow called on the amateur community to be patient
during the AO-40 recovery.

''The good thing is that AO-40 seems to be in a very stable
condition, and there are no signs of further damage,'' Guelzow said
today in a posting to the AMSAT bulletin board. ''However, there is a
sign of a small leak.''

Ground controllers continue to look into the reason for the higher
spin rate as well as into other items under investigation, Guelzow
said, and the results will be reported when the AO-40 team reaches
its final conclusions. He said the priority for now is to get AO-40
back to normal as soon as possible.

AO-40 went silent December 13 while ground controllers were testing
the onboard 400-newton propulsion system. Guelzow's posting did not
indicate whether he thought that propulsion system fuel or some
other substance was escaping through the suspected leak. A computer
reset command Christmas Day brought the satellite back to life, but
telemetry data suggest that AO-40 suffered some damage. Since
Christmas, the AO-40 ground team has been analyzing telemetry sent
via the 2.4 GHz beacon--the only transmitter now operating--to
determine the status of AO-40's onboard systems.

Guelzow said that once the AO-40 team has a handle on the antenna
situation it might attempt  to get the 2-meter and possibly the
70-cm transmitters working. Until then, he said, AO-40 will continue
to use the 2.4 GHz downlink. Guelzow said that because of the
currently limited downlink capabilities, uploading of new commands
and analyzing the results is taking somewhat longer than it would
under normal circumstances.

The AO-40 team also is evaluating the satellite's magnetorquing
attitude control system and wants to spin down the spacecraft and
adjust AO-40's attitude for better sun and squint angles. In
addition, ground controllers will be taking a close look at various
other systems and experiments onboard, including the arcjet and the
stabilization wheels.

''Once this is completed and we have a complete overview, then we can
declare the spacecraft to work normally and perhaps think about
re-defining the mission of AO-40, whatever it will be,'' Guelzow