SATGEN62    WHERE IS DOVE ?    by GM4IHJ   4th June 90

Although perhaps not the choice of all Oscar satellite users, it was clear
shortly after the launch of Dove, that here was a superb simple beginers
satellite. Its 145.825 MHz signal was loud. Its telemetry was highly
informative and, it was easy to copy on readily available terrestrial 2m
packet equipment.

After two months of operating this ideal situation was rudely shattered
when Dove ceased to respond to ground control, failing to switch off its
transmitter to allow ground command to talk to it. In fact Dove's onboard
computer appears to have been hit by Solar or Cosmic ray particles , which
have damaged its memory. When it met this nonsense inserted in its program
/ memory , the computer locked up, leaving its transmitter on, deafening
its control receiver. 

After some good work allround, Dove was illuminated by a very high powered
megawatt transmitter belonging to Moonbouncer W5UN, and after several
tries , it obeyed the ground command and switched its 2m transmitter off.
The problem now is to locate the damaged or altered memory sections and
correct or by pass the mistake . Location depends on dumping to ground ,
what is in the Dove memory, and comparing it with the records of what the
controllers put there originally. But this memory dump cannot come down on
2m or we are back to square one, unable to access the 2m command receiver.
The only possible route is via the Dove S band beacon.

No one as far as I know has much experience or equipment suitable for
reception of data signals from a satellite dopplering at more than 12 KHz
per minute even on a distant pass.  My attempts have not got very far. I
can locate the signal easily . I use a hand held long helix directly
connected to an SSB converter 2400 / 144 MHz feeding an R2000 receiver. At
closest approach the signal is very near 2401.220 MHz for 145.220 MHz on
my receiver. Orbits never coming above 10 degrees of elevation start 30 to
40 KHz higher and end 30 to 40 KHz lower than the cpa value. Orbits coming
nearly overhead shift from more than 50KHz plus at AOS to more than 50KHz
minus at LOS. After many tries I have yet to follow one orbit successfully
from end to end, staying on tune and pointing my aerial correctly. Clearly
any would be data receiver needs a very sophisticated set up.

This is the problem which faces Amsat controllers already working 28 hours
a day to try to get all the right software into the much more obliging
Pacsat and Lusat. Hence the delay. At the moment, the satellite has been
sending unmodulated carrier every time I have heard it this month. So it
may be some time before we get any good news, but please be aware how very
difficult the solution of this problem has turned out to be. Your patience
is requested. Both Dove and Pacsat are presently transmitting on S Band.
73 de John GM4IHJ @ GB7MAC