# Re: GPS for ISS transits and iridium flares

From: Kevin Fetter (kfetter@yahoo.com)
Date: Thu Feb 12 2004 - 14:25:56 EST

• Next message: Thomas Fly: "Re: GPS for ISS transits and iridium flares"

You mean like this:)

Here's the approx area, where the iss will Buzz Jupiter

ISS             20.0 10.0  0.0  0.5 d
1 25544U 98067A   04043.71650473  .00016531  00000-0  15159-3 0  1761
2 25544  51.6266 244.5270 0007160 158.0764 202.1067 15.67023840298639

12 Feb 2004 17:00:00.00          -37.9164          -179.0460
12 Feb 2004 17:00:01.00          -37.8691          -178.9852
12 Feb 2004 17:00:02.00          -37.8220          -178.9242
12 Feb 2004 17:00:03.00          -37.7744          -178.8641
12 Feb 2004 17:00:04.00          -37.7271          -178.8034
12 Feb 2004 17:00:05.00          -37.6796          -178.7431
12 Feb 2004 17:00:06.00          -37.6322          -178.6826
12 Feb 2004 17:00:07.00          -37.5850          -178.6218
12 Feb 2004 17:00:08.00          -37.5373          -178.5620
12 Feb 2004 17:00:09.00          -37.4898          -178.5018
12 Feb 2004 17:00:10.00          -37.4424          -178.4413

This is the predicted path for 0 m elevation in terms of the ellipsoid. The ellipsoid is different
then sea level, so that one thing that must be factored in. For example for my location there's a
diference of approx 32.7 m between the sea level height and the ellipsoid height.

So for example if I am approx 132.7 m above sea level, then I would be 100 m approx above the
ellipsoid. And while SGP4/SDP4 uses the old WGS72 datum, the newest datum is ITRF 2000. So which
datum is used for the obsevers position, will have some effect on the computations.

But then errors in the iss, planet and observer's position will effect the real view.

So I like to compute where the iss will pass approx across a planet, then send out a prediction,
so people can watch the iss pass by the planet fairly close, are it passes a few degrees away. It
makes for a nice view, and people like to watch the show.

The predictions I generate are good enough for me and others, to see something, that all that
matters to me.

If tom generates very precise info, good for him. People can use his info, and get a really nice
view.

Kevin

--- Tom Wagner <wagnert@walnutridge.pvt.k12.ia.us> wrote:

I would imagine that once Tom gets the predictions up for ISS transits of planets,
using a GPS unit will almost be a must!

=====
COSPAR Site #1775  Long 75.6910 W, Lat 44.6062 N, altitude 100 metres

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