On Wed, 4 Feb 2004 07:44:25 -0000, Martin Rowley wrote in

snip
APT = automatic picture transmission; this is the system whereby you can
pull-down imagery as the satellite passes overhead your location; I'm
out of date on all this now (Bernard B. may be able to help), but as a
sproggy Assistant on a lonely island off Oman in the early '70's, we
used to have to go to a little hut at certain times and *manually* point
the aerial array at the NOAA satellites (and we tried for the Russian
Meteor's too), as they passed overhead. You had to work out the
horizon-azimuth, times etc from the NOAA-predicts., then point the array
and wait for the signal. The aerial was tracked as the spacecraft passed
overhead, and the image was downloaded line by line (the spacecraft had
a scanning mirror which acquired the earth-view at the sub-satellite
point), and read onto a facsimile recorder ... then you had to choose
the appropriate lat/long grid to trace on to the image etc.

All a bit of a black art, and I'm sure it's a lot more sophisticated
now!

I'm sure it is, although the basics would be the same. This brings to mind
the setup I used for many years. I had a large dish on the roof above me
for the Meteosat images and an omni-directional antenna for the polar
orbiting satellites, such as NOAA and the Russian ones. I used to be able
to pick them up first when they were at a latitude around central Greenland
and tracked them down to N. Africa. With the type of antenna I used no
tracking was needed.

I had software which would tell me when I should first hear the signals
and, by and large, it was very accurate. The Russian signals had a very
distinctive sound to them, which I can still "hear" even now. The images
appeared on the computer monitor and later printed off. I think Offenbach
(DWD) used to retransmit NOAA images over their FAX system and those used
to be of very high quality when used with the correct FAX paper (made for
such images with all the shades of grey).

I think I stopped around 1994 when online and real time images started to
become available.

--
Mike 55.13°N 6.69°W Coleraine posted to uk.sci.weather 04/02/2004 09:32:35 UTC
Temp +8.3C and rising.