Satgen 440  Long Live Oscar Ten  by GM4IHJ    (BID SGEN440)  30Aug 97

With the news from Phase 3D varying from bad to very bad, it is
encouraging to find that Oscar Ten , the first Phase 3 satellite to
make it into orbit , is still providing occasional service . Launched
in June 1983 , Ao10 has suffered more than most , having endured mode
L failure , followed by loss of command and control, it none the less
keeps returning to a very useful operational mode B status every 5
months or so for 70 to 100 days of operation followed by about 60 to
80 days of silence. This latter inert state being occasioned by its
attitude in space producing very little sunlight on its solar panels'

Presently Oscar Ten is with us, seeing lots of sunlight and working
well, so perhaps a review of its general characteristics may be
useful.
Uplink   435.19 to 435.04 MHz LSB or CW to an inverting transponder
Downlink 145.815 to 145.965 MHz USB or CW 
Beacon 145.81 MHz constant carrier , no modulation

Ao10 does exhibit marked signal fading , which occurs as the changing
aspect of the slowly spinning satellite ( circa 0.4 rpm), causes
variation in the sequence of signal fades at ground receivers. In a
typical example at mean anomally 196 the beacon signal is nearly fade
free, but by ma 212 a 3 fades per rotation of the satellite pattern of
fading is very evident, as the 3 corners of the satellite
consecutively pass between the satellite downlink antenna and the
ground station line of sight. Then later at ma 228 , the triple spin
fade roughly ever 2.3 minutes, has almost disappeared again. A
sequence which differs from time to time as the observers view of the
satellite changes over several days.

As stated above the satellite seems to be spinning at about 0.43 rpm,
and signal fades due to sat antenna screening are usually about 12 dBs
deep, but can at times be as much as 20 dBs deep, as one corner out of
the three causes much more complete blocking of the signal path than
the other 2 corners.

When seeing adequate sunlight, the Ao10 beacon signal is relatively
steady even when hi power uplinks are present on the transponder. But
as the satellite sees less and less sunlight its beacon begins to FM.
Showing cyclic modulation of frequency of about 20 Hz bandwidth. Then
as the solar illumination deteriorates further the beacon begins to FM
much more widely reaching shifts of 150 to 200 Hz at times, rendering
use of the transponder almost impossible. Soon after this the beacon
and all Ao10 services can be off for up to 2 or in rare cases 3 months
at a time, before return to a more sunlit attitude gradually restores
the satellite and its beacon to useful mode B operation. These changes
are not easy to predict. 

So please use Ao10 carefully while you can and keep hoping that it
keeps returning to operational status for a few more years. 

One anomaly you may hear sounds like key clicks when the downlink and
beacon are particularly strong (Eg at perigee),but they do not seem to
cause any harm.