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ARRL Satellite Bulletin ARLS015 (2001)

ARLS015 AO-40 "S1" Transmitter Goes Silent

QST de W1AW  
Space Bulletin 015  ARLS015
From ARRL Headquarters  
Newington, CT  August 14, 2001
To all radio amateurs

ARLS015 AO-40 ''S1'' Transmitter Goes Silent

AMSAT reports the 2.4 GHz ''S1'' transmitter aboard AO-40 has gone
silent. Ground controller Stacey Mills, W4SM, says the transmitter
abruptly quit August 13 at around 1258z while AO-40 was in view of
most of the Eastern Hemisphere during orbit 362.

He reports normal telemetry readings up to the point that the
transmitter ceased operating and that no commands were being sent or
experiments under way at the time.

An onboard scheduler switched on the S2 transmitter at the
appropriate point in the spacecraft's orbit. Mills said subsequent
telemetry indicated no abnormalities or logged events to account for
the failure.

The S1 transponder, connected to a higher-gain parabolic antenna,
had been brought into the rotation to offer improved coverage when
the satellite was farther away from Earth. The S2 transponder is
connected to a helical antenna that has about 10 dB less gain than
the parabolic antenna.

An initial attempt to manually switch the S1 transmitter back on did
not appear successful. While ground controllers continue to study
the situation, the S1 transmitter has been taken out of the
schedule. The U-band and L1-band to S2-band transponder passbands
will remain active from MA 10 to MA 30 and MA 44 to MA 100. The
RUDAK digital transponder is connected to the S2 transmitter, and
the beacon is off from MA 30 to MA 44.

''The schedule may also be modified for longer passband periods,
given the broader coverage of the S2 helical antenna,'' Mills added.

For more information on AO-40, visit the AMSAT-DL Web site, or the AMSAT-NA Web site,


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