Satgen 10   Measurement of Timings of AOS , LOS and CPA/TCA

When trying to workout the orbit period of a new satellite, several
commentators suggest using  successive timings of either AOS Acquisition
of Satellite as it comes above your station horizon, or , LOS, Loss of
satellite as it drops below your station horizon. This often leads
to serious errors. The problem is threefold. Firstly by using AOS or LOS
you are making your measurement when the signal is weakest. Secondly you
are ignoring Atmospheric Refraction which can bend signals 1.5 degrees at
the horizon. Thirdly , few stations have flat 0 degree elevation horizons
all round. At IHJ horizon varies from + 0.5 to +6 degrees depending on 
azimuth. An error of 1 degree on a low elevation pass can give you timing
errors of over a minute. So a future Satgen will outline the accurate
method of timing orbits using CPA Closest Point of Approach.

Shorts   MIR . The Soviets have now reported that before leaving Mir the 
Cosmonauts changed the battery to try to eliminate the problem, but that
did not cure it. They have not announced what they propose to do next,
meanwhile the Americans are speculating wildly. At BIS Astronautics 
Symposium , David Shayler revealed that on last flight Cosmonauts had a
much improved spacesuit - which explains why EVA communications speech
quality, suddenly improved dramatically .
Salyut. At BIS Philip Clarke tabled the serious problems facing the
Soviets if they try to carry out the proposed recovery to earth  of the
Salyut station by their Shuttle. Soviet economic problems being what they
are , it could well be that this expensive proposal wiill be cancelled.
Frequency Queries. Soviet Electronic intelligence satellites crossing UK 
airspace roughly every 20 minutes, transmit simultaneously on two
harmonically related phase locked frequencies, either 153.42 and 204.56 
or, 153.48 and 204.64 MHz.Soviet Spy Packet Store and Forward sats
transmit simultaneously on 153.6 and 204.64 MHz. But while ELINT birds are
on all the time, the covert store and dump sats only transmit/dump over
Moscow.
MARS. There is still no answer as to why the Phobos mission went into a
spin and lost Earth lock for communications. At BIS symposium P Hansson
reviewed latest Soviet Space medicine thinking about effect of Cosmic
Ray bombardment on Cosmonauts - the answer if unprotected , is serious - 
This is probably biggest problem for Mars Mission. Passive shielding
protection offers little hope of reducing problem, but Active Electrical
shielding looks helpful and strangely enough it also helps to go when Sun
is very active , because strong Solar wind reduces Cosmic ray level, and 
Solar wind proton shielding is easier to achieve than cosmic ray
shielding.      73 de GM4IHJ on 6th June 89