Satgen 448  Lighten our Darkness  by GM4IHJ   (BID SGEN448)  25 Oct 97

Recent mail into IHJ, suggests, that a lot of European satellite users
are interested in LEO Weather satellite pictures. But , presently find
the results they are getting are rather puzzling - Sats not
transmitting, or , dark pictures. 
Tackling sats not transmitting first . This applies to the Okean and
Sich sats, and the Meteor sats. Okean and Sich only broadcast at rare
times, this is their pattern of operation and will not change. You can
get advanced warning of Okean schedules on European amateur packet BBs
Met 3-5 is different. It is only switched on when the ground beneath
it is well lit by the sun.  Eg 22 Oct 97 1002utc 3-5 above IHJ
northern horizon overhead 81N 92W - 6 hours in suntime behind UK and
over the north pole in October when the solar terminator has already
descended to 72N over Europe. Indeed the satellite is coming east but
does not see sunlit ground until 1011ut at 58N. As the IHJ software
reveals. So you get no transmission until the sat is south of 58N, and
by December there will be none until it descends below approx 50N.

In addition to the above restriction, even when it switches on at 58N.
the sat picture covers 4 time zones. To the east it is moderately
sunlit. To the west it is muddy brown and indistinct. By January
however the concerns will be quite different. Met 3-5 orbit is not sun
synchronous and in early 98 it will be in a plane ascending south to
north around noon time local. So IHJ should have a picture from
satellite acquisition . BUT will lose it as the sat goes over UK
heading north and automatically decides it is not seeing enough
sunlight , and so switches off.
Note these features apply to 3-5, other Meteors if operational, will
be in different orbit planes.

Operational VHF Noaa sats are presently 12 and 14. Noaa12 is hopeless
. Its orbit plane is now very close to the dawn dusk line . So half
your picture is always dark. 

Noaa14 by contrast has an orbit plane which ascends about 90 minutes
after local noon, an almost optimum situation . OK on Saturdays and
Sundays but not so good for most working folks over the rest of the
week. Again however high latitude stations must be aware that even a
noon ascending orbit runs out of strong sunlight as it climbs above
50N in December , (58N in November or January) . So do not expect to
monitor the weather to your north effectively on the visual display.
There is always the Infra Red display but that is far more difficult
to interpret and far less interesting than the visual display

There is a bonus . But not until the northern summer. When a super
sunlit pole gives excellent results 20 hours a day at IHJs 56N.
Meanwhile, for those who cannot wait until summer . Okean does provide
some short transmissions where the visual is often totally clouded
out, but the narrower multi spectral displays of what looks like side
scan radar, do give you a picture of some of what you are missing in
the visual light display window.
Many thanks to all who sent constructive replies about Satgen 447
Amsat Problems. Will try to review answers received, shortly.