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ARRL Satellite Bulletin ARLS003 (2001)

ARLS003 AO-40 Report Suggests Damage to Antenna Systems

QST de W1AW  
Space Bulletin 003  ARLS003
From ARRL Headquarters  
Newington, CT  January 16, 2001
To all radio amateurs

ARLS003 AO-40 Report Suggests Damage to Antenna Systems

The latest information on AO-40 suggests that the satellite might
have suffered antenna system damage when it went silent last
December 13. The satellite stopped transmitting while ground
controllers were testing the 400-newton propulsion system.

AMSAT-DL Vice President and AO-40 team member Peter Guelzow, DB2OS,
reports that efforts to restart the 2-meter transmitter continue to
be unsuccessful. The satellite had been sending telemetry via the
2-meter transmitter when it quit transmitting last month.

Guelzow said this week that while the 2-meter, 70 cm and 1.2 GHz
receivers are working on the high-gain antennas, none of them will
work on the omnidirectional antennas. He speculated that either the
omnidirectional antennas or the cabling or the antenna relays are
damaged. Additional tests will be carried out, he said, including
testing the VHF transmitter using the omnidirectional antennas.

Plans also call to test the 70-cm transmitter on both the high-gain
and omnidirectional antennas, once the spacecraft's spin rate has
been reduced and AO-40's heat-dissipation mechanism is working

Guelzow said that AO-40's attitude control system is fully
functional--something that would be critical to keeping the
satellite in orbit on a long-term basis. But, the sun sensor's
electronics have quit working, and, Guelzow said, without sun and
attitude information, no magnetorquing can be performed.

AO-40 team leader Karl Meinzer, DJ4ZC, was reported to be developing
a software fix that does not rely on data from the sun sensor. It
will be tested soon.

Guelzow expressed the hope that once the sun angle and
antenna-pointing capabilities have been established, the ground
crews will have a better chance to check out the status of the 2
meter and 70 cm transmitters through ''better-controlled and suitable

He indicated that AO-40's arcjet thrusters and the reaction wheels
also will undergo testing as soon as possible.


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