[amsat-bb] Re: ISS keps

Ransom, Kenneth G. (JSC-OC)[BARRIOS TECHNOLOGY] kenneth.g.ransom at nasa.gov
Thu Sep 23 05:05:24 PDT 2010

The ISS did some thruster tests recently. That could account for the difference. ISS is a dynamic satellite. It has minor and major changes to its orbit and the "predicts" are sometime a bit behind the actual until things fall into a more stable state and get updated. I expect the numbers will be off again after the Soyuz undock today (tomorrow UTC).

Kenneth - N5VHO

-----Original Message-----
From: amsat-bb-bounces at amsat.org [mailto:amsat-bb-bounces at amsat.org] On Behalf Of Patrick STODDARD (WD9EWK/VA7EWK)
Sent: Wednesday, September 22, 2010 4:18 PM
To: amsat-bb at amsat.org
Subject: [amsat-bb] Re: ISS keps

(after seeing weirdness in the message I sent, I will try it again so it looks

> I checked against http://iss.astroviewer.net/.  Today issue is better,
> however, still actual ISS posn about 100 miles ahead of SatPC32's displayed
> posn.  My computer clock is off by no more than 1 second.  For the clock to
> throw posn off by 100 miles, clock would need to be in error by about 15
> seconds.

Just create an account at http://www.space-track.org/ and download the keps
from there.  I just logged into Space Track, and they have an ISS element
set that was updated at approximately 2053 UTC today (not long before I sent
this message).

Regardless of the freshness of the elements, it sometimes takes a little
bit after the ISS has a boost raising its orbit to where the keps are back
to being on the mark.



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