Satgen 401  Oscar Ten Prospects ?  by GM4IHJ  (BID SGEN401)  30 Nov 96

With the shut down and imminent death of Oscar 13, old timer Oscar 10,
becomes amateur radios only Molniya high altitude elliptical orbiter.
Ao10 operates spasmodically- good for say 2 months then bad for 3
months or so, on mode B 435 Mhz up 145 Mhz down CW and SSB. When
working properly as it was up to November 25th, Ao10 can provide
excellent long range DX contacts, but it no longer obeys ground
commands . So it very slowly drifts giving useful performance for 2
months or so , before going through a sequence of FMing- then
apparently dead, then FMing again, taking perhaps 3 months before
returning to useful performance once again.
This odd behaviour is perhaps best shown in the following record:-

Date   Shadow for  Solar to Sat      Solar + Sat      Condition
1996   part orbit  Separation Angle  Footprint Angle
                   Min      Max      Min     Max
26Jun     NO        47      131      142     171      FMing badly

7 Aug     NO        37      141      142     171      FMing badly

15Sep  Yes 40 mins  11      170      142     171     Stable if sunlit

11Oct  Yes 32 mins  13      167      142     171     Stable if sunlit

25Nov     NO        43      136      142     171      FMing

Please note the paradox here. Best results occur when Ao10 spends part
of its orbit nearly under the sun, even though it goes into shadow in
the other part of the orbit and temporaly shuts down completely. In
the June/Aug/Nov orbits the sat never goes into shadow but its minimum
separation from under the Sun is much greater. So it may be the case
that a half orbit burst of strong direct sunlight is better than an
orbit of indirect sunlight.

The last full period of FMing or continuous shut down lasted about 100
days. The subsequent operational period has lasted about 70 days, and
we now appear to be entering another period of continuous FMing. 

There is no clear evidence that using the transponder when it and the
beacon are FMing slightly, does the satellite any harm . Eg presently
the beacon excursions with 7 QSOs on the sat are about 30 Hz max. But
in the previous FMing incident the beacon excursions reached 200 Hz or
more when operators began to access the transponder. 

So , it is possible that Ao10 will gradually become more difficult to
use over the next few weeks , and it may even shut down completely as
it did in late July 96, when not even the beacon was audible at
perigee. Actual forecasting is difficult but the satellite begins to
experience half orbits nearly directly under the Sun, from mid
February 97 onwards. Who knows ? IHJ will be around if it does stop
FMing, and meanwhile will report Ao10 status regularly in Satgens.