Date   : Tue, 31 Aug 2004 23:53:08 +0100 (BST)
From   : Pete Turnbull <pete@...>
Subject: Re: Astrid satellite receiver

On Aug 31 2004,  8:23, Jules Richardson wrote:
> On Tue, 2004-08-31 at 00:21, Pete Turnbull wrote:
> > I had a magazine reprint and possibly some other info about it.
 I'm
> > sure that had information about antennae.  I'll have a look.

> Well some info I dug up on the web implied that it was designed to
work
> with both UoSAT1 and UoSAT2 - UoSAT1 died after only a couple of
years
> by the sounds of it due to the batteries used, but UoSAT2 was still
> going in 2002 according to a Usenet post I found.
>
> There's a switch on the front labelled data 1 and data 2 - maybe
that's
> to flick between the different satellites (or something else entirely
> :-)

OK, I found the documents, such as they are.  ASTRID was designed by
one Stephen Webb, who ran a company called M.M.Microwave (and
M.M.Technology and others: their real business was making military
radar and missile components) in Kirkbymoorside, not so very far from
here -- but they're not around now (or at least not in the same place).

ASTRID stands for Automatic Satellite Telemetry Receiver and
Information Decoder, and cost £129.57 + VAT (£149).  The system
consisted of the receiver box, aerial with standard TV-type downlead
and coax plug, mains PSU (nominal 12V-14V DC), connecting leads for a
mono tape recorder and computer serial port, software and handbook.

It's designed to receive ASCII digital telemetry data from the UoSAT1
and UoSAT2 satellites on 145.825MHz; bandwidth is 12kHz.  It decodes
the signal into tones and these can be recorded on tape or passed back
into the ASTRID circuitry and decoded into a serial data stream at 1200
baud (7E1), as well as listend to on the audio output (8-ohm speaker).
 It's reputed to be unusually sensitive and the antenna doesn't need to
be steered.  The antenna and cable it comes with is 75ohm, but it says
it can be used with 50ohm ones.

Since the UoSAT?s are polar orbiting (UoSAT2 is OSCAR-11), you'd only
pick up a signal (with the antenna pointing more or less straight up)
when a satellite was in range; when ASTRID detects a signal it switches
on the tape recorder.  Everything else is automatic.

If the tape recorder is connected, it will record the data; if there
are no plugs in the MIC and EAR sockets then the data will be decoded
and come out the serial port (which is actually a TTL port, not RS232,
on most versions).  Normally you'd record the signal using the MIC
socket and then play it back into the EAR socket later, to get it
decoded, using the pause control on the tape as required.  If it's
receiving a live signal while you're playing back a recording, it puts
the live signal out the MIC socket while decoding the recorded one
you're playing back into the EAR socket.

There's some info on UoSAT2 on the University of Surrey's pages, and
pages linked to from there.

www.ee.surrey.ac.uk/SSC/CSER/UOSAT/missions/uosat2.html
http://www.users.zetnet.co.uk/clivew/oscar11.htm>
http://science.nasa.gov/Realtime/JTrack/3D/JTrack3D.html

If you remind me of your address, I'll post you photocopies of the
meager info I have.

-- 
Pete                                           Peter Turnbull
                                               Network Manager
                                               University of York