[jamsat-news:1415] AMSAT Special Bulletin 008.01

[Dan James <DanJ@marvin.com>]

SB SAT @ AMSAT $ANS-008.01
PHASE 3D/AO-40 UPDATE

AMSAT NEWS SERVICE BULLETIN 008.01 FROM AMSAT HQ
SILVER SPRING, MD, JANUARY 08, 2001
TO ALL RADIO AMATEURS
BID: $ANS-008.01

AMSAT-DL President AMSAT-DL President Karl Meinzer, DJ4ZC,
provided ANS with the latest information about AMSAT OSCAR 40:

Greetings,

Since my report from late December, command stations have
implemented the strategy which I had outlined. The first priority was
to determine which command-uplink channels were available. This
work was difficult, very time consuming (and for the satellite) somewhat
dangerous due to the unknowns. The command stations did a
magnificent job! Due to their combined efforts I can report the
following findings:

1. After some blind transmissions to test the omni-antennas around
apogee (that failed to produce a response), the scheduler was activated
and programmed in such a way as to prevent lock-out. This strategy
turned out to be very prudent and the scheduler-operation went smoothly
and resulted in no additional anomalies.

2. The scheduler then took AO-40 through a number of modes, which
allowed the P3D team to determine the following: 
		a. 	V, U and L-1 receivers work
		b. 	V, U and L high-gain antennas work
		c. 	U and L low-gain antennas do not work
		d. 	the status of the V-band low-gain antenna has not
been finally
		      determined. Apogee blinds tests are in progress as I
write this
		      to accurately determine the status of this antenna

3. 	The V-band transmitter was operated for one MA-unit. It demonstrated
a marked temperature increase, but no signal was heard. This was a
quick-look test and this result should not be considered final. Further
tests
will be necessary (including the need to determine if the matrix was set
properly). These tests will have to wait until the spin rate is reduced to
ensure that the satellites heat-pipes will be able to handle the dissipation
for extended periods.

4. Magnetorquing was started to reduce spin and the first indications are a
loss of around 0.5 rpm - roughly consistent with theoretical predictions. We
can conclude that the system works. In order to use Earth-sensing data, a
small additional program needs to be installed which stores data at apogee
for later recovery when telemetry reception becomes available.

What's next?

During the next days the attitude control system should be returned to full
functionality. It will be used to reduce the spin to a value consistent with
heat-pipe operation and also with the requirements to change attitude.
These changes are necessary for sun-angle constraints, communication
access and also to reduce the effect of our ongoing mass-loss on perigee
altitude. Newer model calculations show that the mass loss could be larger
than my previous estimates; thus it would be prudent to use the resulting
thrust to increase perigee altitude (right now it is decreasing it).

Once the spin/attitude situation is under control, we will continue the
check-out of other systems (such as):

1. Determine the status of the V-band transmitter (controlled experiments)
2. Determine the status of the U-band transmitter
3. Determine the serviceability of the ATOS (Arcjet) to determine if it can
    be planned on for a strategy toward an improved orbit
4. Test the momentum wheels to determine if AO-40 can be put into a
    three-axis mode which would greatly reduce the impact of the loss of the
    omni-antennas

Present data so far indicates that although we have lost some systems
in AO-40, there has been no further deterioration after the second incident.
In particular, if ATOS and three-axis stabilization are still serviceable,
AO-40 will still be able to produce a large fraction of the Amateur Radio
service expected from it.

Personally, I am optimistic and I believe that the command-and
engineering team stand a good chance of turning AO-40 into an
extremely useful Amateur Radio satellite.

73, Dr. Karl Meinzer, DJ4ZC

Stay tuned to ANS, the official source of information on AMSAT
OSCAR 40.

[ANS thanks AMSAT-DL and AMSAT-NA for this information]

/EX

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