ARRL

ARRL Satellite Bulletin ARLS005 (2004)

SB SPACE @ ARL $ARLS005
ARLS005 A glimmer of hope for AO-40

ZCZC AS05  
QST de W1AW  
Space Bulletin 005  ARLS005
From ARRL Headquarters  
Newington, CT  March 11, 2004
To all radio amateurs

SB SPACE ARL ARLS005
ARLS005 A glimmer of hope for AO-40

A weak "noise" on the AO-40 2.4-GHz beacon frequency has raised
hopes that AO-40 may still be alive. AO-40 has been silent since
January 27 (UTC), in the wake of a precipitous voltage drop. The
satellite's controllers believe that one or more shorted battery
cells are at the root of the problem.

Colin Hurst, VK5HI, of the AO-40 command team reports that on March
9 between 0310 and 0320 UTC (orbit 1541) he "noted a noise peak of 4
to 5 dB" in the vicinity of the expected beacon frequency after he'd
issued a transmitter reset command sequence to the satellite. "The
width of this peak was about 5 kHz," he said. After listening for
about 15 seconds, he issued a command to shut down the transmitter,
and the noise peak disappeared.

Hurst said he also transmitted several commands involving the
auxiliary batteries but did not attempt to turn the beacon on again.
"This tends to suggest that the IHU [Internal Housekeeping Unit
computer] and L Band [1.2 GHz] receiver are operational," he said.

The AO-40 command team theorizes that a cell in the main battery
pack has shorted, clamping the bus voltage below the point where it
can operate the satellite. The spacecraft's auxiliary batteries are
believed to be in parallel with the main batteries, and commands
sent so to swap to the auxiliary batteries have been unsuccessful.
AO-40 Earth stations are continuing to send commands to the
satellite in order to switch the batteries.

Updates on AO-40 are available on the AMSAT-DL Web site,
http://www.amsat-dl.org/journal/adlj-p3d.htm .
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