Satgen285  Satellites for Experiments  by GM4IHJ            10th Sept 94
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Some satellites perform well in a wide variety of experiments. Others are
perhaps very good for one particular experiment but no use for others. In
addition , amateur satellites are not always the best vehicles for some
experiments , so experimenters may have to use commercial or military
satellites if these are available. Example are :-
Doppler experiments are best done on VHF or UHF satellites which transmit
a continuous uninterupted CW carrier.The best and most numerous sats with
this characteristic are the LEO Navigation sats which use 399.2 to 400.2
MHz band. But if you cannot use the navsats , RS10 and RS12 on 29.358 and
29.408 down are the next best and most simple. RS14 on 145.821 CW down is
a good bet if you have VHF reception and FO20 is also very good if you can
receive 435.795 MHz ( these latter two sats also have much greater doppler
shift than RS10/12 ).
For experiments to examine Faraday rotation of signal polarisation, the HF
sats RS10 and RS12 are not the best. They have too many polarisation
changes in a pass and it is sometimes difficult to mount the large
separate vertical and horizontally polarised dipoles necessary for a good
experiment. 145 MHz sats UO11 , AO17 and RS14 make excellent Faraday
targets , but the next higher frequency sats at UHF ( AO16, AO18, AO19 and
FO20 ) are not good targets because they have too few faraday rotations of
polarisation in a typical satellite pass of your station.
Scintillation experiments require a different approach . For while it is a
common phenomena when signals transit through the equatorial or polar
ionosphere, it is uncommon on signals transitting the middle latitudes
ionosphere. So signals from the satellites with near polar orbits ( ie
most sats except Shuttle, Mir and a few specials with low orbit
inclination) , are the best scintillation targets with FO2O being a
particular favourite on 435.795 MHz downlink. 
Ionospheric transparency by contrast , requires a satellite which is
moving very slowly or not at all . AO13 might appear at first to be
useful, but its mode changing usual precludes a complete experiment at any
one frequency. Old geosats using 136 MHz down were the best target, but
VHF is no longer used from geostationary orbit because it was regularly
ruined by Sporadic E. So the best bet in 1994 is the military Fleet Satcom
birds which have several channels in the band 240 to 270 MHz.
Satellite spin experiments usually require equipment for decoding
telemetry of say solar panel currents. If a modem and decode software is
available Dove AO17 gives good results and at UHF sats AO16 and AO19
make an interesting comparison as they spin and point their opposite ways
around the earth.
Last but not least are the mystery sats. One starts by tracking known sats
Learning how to use orbit timing to get your own orbital parameters
and classification data, first. Before tackling the absolutely unknowns.
Several unknowns have appeared in the amateur bands in recent years with
Hilat and Polar Bear being perhaps the best examples. If you can detect ,
classify and identify an orbiter for yourself , you are perhaps truly able
to call yourself a first class satellite hacker or experimenter. 73 de
John GM4IHJ @ GB7SAN