AO-40 transponders off in preparation for orbit shift

From the ARRL...



Ground controllers for AO-40 have shut down the satellite's
transponders as preparations continue for a slight shift in orbital
configuration.



''Due to changes of the spacecraft latitude for the arcjet cold
firing, the squint pointing angle is more than 30º and not currently
useful for transponder operation,'' said AMSAT-DL President and
AO-40 team member Peter Guelzow, DB2OS. ''Therefore we have
suspended transponder operation for now and give the RUDAK team more
access.''



Guelzow said the S2 transponder will remain off ''until further
notice.'' The RUDAK beacon and the 2.4 GHz middle beacon will remain
up.



Plans call for raising the AO-40's perigee by approximately 200 km.
AMSAT-NA President Robin Haighton, VE3FRH, said ground controllers
will use magnetorquing to adjust AO-40's attitude to 270/0, then
fire the arcjet using only ammonia fuel.



Haighton said it's hoped that a slightly higher perigee for AO-40
will eliminate the effects of what he described as ''a mysterious
force'' that alters the satellite's attitude when it comes through
perigee.



Ground controllers also have suspended for now further testing on
the X and K band transmitters and C band receiver.