ARRL

ARRL Satellite Bulletin ARLS007 (2001)

SB SPACE @ ARL $ARLS007
ARLS007 AO-40 Transponder Operation Possible This Summer

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QST de W1AW  
Space Bulletin 007  ARLS007
From ARRL Headquarters  
Newington, CT  April 27, 2001
To all radio amateurs

SB SPACE ARL ARLS007
ARLS007 AO-40 Transponder Operation Possible This Summer

AMSAT-NA President Robin Haighton, VE3FRH, has raised the
possibility that AO-40 could inaugurate transponder operation this
summer, if tests and orbital maneuvers between now and then go as
planned.

''We are learning how to fly this thing,'' Haighton said. ''But I still
think we're going to end up with a darned good satellite.''

The most likely initial transponder configurations, Haighton said,
would be Mode L/S--1.2 GHz up and 2.4 GHz down, Mode U/S--435 MHz up
and 2.4 GHz down, and possibly Mode V/S--145 MHz up and 2.4 GHz
down.

Recent data suggest that the mid-December incident that silenced
AO-40 for two weeks and rendered some systems unusable also might
have blown a hole on the 400-newton motor side of the spacecraft.
''Speculation is there could be damage, and sunlight is getting right
in,'' Haighton said. He noted that ground controllers have detected a
distinct rise in temperature when sunlight strikes that side of the
satellite.

Ground controllers plan to raise the height of the perigee in the
very near future, Haighton said. That process, using the onboard
arc-jet motor, could take up to several weeks. The AO-40 team hopes
the maneuver will minimize or eliminate possible effects on the
satellite's orbit caused by atmospheric expansion at the peak of the
solar cycle.

AO-40 currently is approximately 320 km--almost 200 miles--above
Earth at perigee--its closest point--and some 51,000 km--some 31,600
miles--at apogee. Plans call for raising the orbit at perigee to
around 520 km, or some 320 miles.

Once the orbit has been adjusted, ground controllers would orient
the spacecraft's attitude and check out the various onboard
transmitter and receiver systems to see what works and what does
not. ''We're still pretty confident that the 2 meter and 70 cm
transmitters are not there,'' Haighton said, ''but we're equally
confident that the receivers for those bands still are.''

The satellite has been transmitting telemetry on the 2.4 GHz (S-2)
beacon, and signals reportedly have continued to improve--although
the beacon has been out from time to time as needed to conserve
power during eclipse periods.
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