ARRL

ARRL Satellite Bulletin ARLS011 (2001)

SB SPACE @ ARL $ARLS011
ARLS011 AO-40 Now in Long-Term, "Safe" Orbit

ZCZC AS11  
QST de W1AW  
Space Bulletin 011  ARLS011
From ARRL Headquarters  
Newington, CT  July 11, 2001
To all radio amateurs

SB SPACE ARL ARLS011
ARLS011 AO-40 Now in Long-Term, ''Safe'' Orbit

AO-40's new orbit should be good for at least the next 20 years,
according to AMSAT-DL President Peter Guelzow, DB2OS, who heads the
satellite's ground team. Following maneuvers to shift the
satellite's orbit at perigee, AO-40 perigee now is ''oscillating in a
safe range between 810 and 1260 km,'' Guelzow said.

AO-40's height at apogee--58,971 km--was unchanged by the orbital
adjustment. The satellite's transponders remain off as ground
controllers reorient the spacecraft. Still in question is whether
ground controllers will be able to deploy the satellite's solar
panels.

Ground controllers were able to change AO-40's orbit through
successive ''cold'' firings of the onboard arcjet motor--using only
ammonia gas. The move raised AO-40 some 300 km higher than
predicted, but it apparently depleted the spacecraft's ammonia
supply. As a result, AO-40 likely will remain in its current orbit.

Stacey Mills, W4SM, of the ground team said it's ''quite possible''
that an ammonia leak accounted for the unexpected loss of ammonia.
''If we did have a slow leak, it is very fortunate we did not wait
any longer to use the remaining fuel,'' he said.

Mills said that AO-40's old orbital configuration, while stable, was
too close for comfort at perigee.

''I sincerely hope that nothing else malfunctions for a long, long
time, but this is, after all, rocket science,'' Mills said. ''Nothing
is guaranteed.''

Ground controllers plan to fully test AO-40's momentum wheels prior
to any decision to deploy the spacecraft's solar panels. The
momentum wheels provide three-axis control of the spacecraft. If the
momentum wheels are not operational, it's unlikely the solar panels
will be deployed.

For more information on AO-40, visit the AMSAT-DL Web site,
http://www.amsat-dl.org/ or the AMSAT-NA Web site,
http://www.amsat.org. AMSAT-DL now offers an AO-40 ''Quick Status''
page.
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