Satgen 8    Scintillation studies using the Polar Bear 105 min orbiter.
   Satellites in motion produce a doppler shifted signal.
If the direct path signal is deflected away from you by disturbed
ionosphere,you get signal via a different, bent, path , with a different
doppler shift.So as the sat goes north of UK,its clear dopplering note may
suddenly become a jumble of different notes as the signal path flickers.
This is scintillation. Heard from UK at any time of day ,as the signal
path cuts the Polar Front , whether there is an Aurora or not.The degree
of scintillation and its location ,are a guide to state and location of
the Polar Front.
Specimen Polar Bear orbital track for Polar Great Circle Plot Users
EQX+  Lat   Long     Min   Lat   Long     435.974 MHz Tx centre Frequency 
0 min 0     0        28   84.08  191.27
 2    6.84  0.449    30   77.24  189.46
 4   13.69  0.90     32   70.38  189.26
 6   20.54  1.34     34   63.53  189.41
 8   27.39  1.78     36   56.67  189.70
10   34.24  2.21     38   49.82  190.05
12   41.09  2.63     40   42.96  190.44
14   47.94  3.03     42   36.11  190.85
16   54.79  3.39     44   29.25  191.28
18   61.64  3.70     46   22.40  191.72
20   68.49  3.90     48   15.54  192.16
22   75.35  3.84     50    8.68  192.61
24   82.19  2.81     52    1.82  193.05
26   88.96  341.6    54  - 5.03  193.50
Period 105 minutes ,inclination 89.56 degs,increment per orbit 26.32 degs
Approx EQXs are :- 24th May 1134ut at 344.5 degs West. Add 105 min and 
26.32 deg for subsequent orbits that day. Add 30 mins and 7.5 degs for 
each subsequent day. Remember 2nd sat on same frequency has quite 
different orbit. It appears 26 min early each succeeding day.
Do not mix the two sats.
The above track can be marked out on an acrylic overlay , and rotated 
round a pin centred on a North Pole Great Circle Map, for EQX tracking.
In range footprint has 30 deg radius round your station.
Why bother about Scintillation ?. Because it very seriously degrades
CW, RTTY, Voice, TV and Radar signals. By contrast it hardly affects BPSK 
and/or High Speed Digital Packet. Scintillation occurs, over the Equator
, near the Poles , and in deep space beyond the Earth.
Shorts   MIR -   Now regularly replies to ground , using noisy telemetry
on 166.122 MHz sent at eastern end of orbit track after it has passed UK.
Clear skies may give good Mir visual passes , west to east. Centred on 
south at 2318 ut on 24th and 0053 ut on 25th (eg BST 0018 and 0153 25th)
For each extra day add 44 mins and or subtract 49 mins from these times.
Actual time will differ depending how far east you are (later) in UK
SALYUT. I thought it was lost , but it has shifted frequency up 2KHz to 
19.957 MHz.Was trackable subhorizon UK to OZ, 1950 to 2028 ut 23rd May
Salyut is likely to be visual 26 to 28 mins after above Mir timings.
RS 10  Giving super downlink now AGC limiter is off. Listen above 29.357
UOSAT 1 . Have not heard the 29.511 beacon lately. 73 de GM4IHJ 24May 89