re: Milstar TLE's

Philip Chien (
Tue, 4 Feb 1997 20:17:56 -0500

Bruno Tilgner <100533.2016@CompuServe.COM> said:

>One of the easiest-to-observe geostationary satellites must be MILSTAR DFS 2
>because of its huge size of about 50 m. This is surely an ELINT satellite
>for eavesdropping on wireless communications all over the eastern hemisphere.

Nope, just a plain o'le comsat.  Well, the world's largest geosync comsat
and some pretty nifty capabilities.  Given the amount of unclassified
documentation and photographs I have of it, I'd highly doubt that it's got
any ELINT functions which I'm not aware of.

The only 'black' payload was a relay function, supposedly for the LEO
reconsats to transmit back data.  DFS-1 did have a black payload on board
which was tested, but is not in use due to the end of the Cold War.  On
DFS-2 it was replaced with ballast, which was incorrectly thought to be
"sand" according to a Los Angeles Times story.  Furture Milstar satellties
will use a different design which won't have an empty space onboard.

>The TLE's in Ted Molczan's file for this satellite are from 18 July 1996
>(96200). Whilst this age is probably not a serious problem for geosats,
>I wonder whether there are not more recent observations.

For true geosync satellites it should be fairly easy to just use the simple
trig equations for aiming satellite dishes at geosynchronous satellites and
use the azimuth and elevation, you really don't even need to use a tracking
program.  There are several freeware and shareware program for calculating
look angles for geosync satellites, just input your latitude and longitude,
and the longitude of the satellite you're interested in, and the program
returns the azimuth and elevation.  I use a spreadsheet I generated myself,
but there are plenty of programs available.

Milstar is three-axis stabilized so it should appear as a fairly steady
object.  Some geosync satellites are spin stabilized, most notably the
HS-376 and HS-393 designs, these will flash at a constant flash rate.

And, of course, there are the ones which flash at semi-random rates because
they're tumbling on more than one axis.

We call those the non-functional satellites.  ;-)

Philip Chien, KC4YER
Earth News - space writer and consultant
note new E-mail address -