Practical limits of SDP4
Tue, 28 Jul 1998 07:29:16 -0500 (CDT)

Jason wrote:

>Hi All,
>		I was wondering what the practical limits of the prediction algorithms
>used in tracking software are for satellites in "deep space" orbits. I
>know that SDP4 works quite well for satellites in geosynchronous orbits
>(ie. 36,000km alt) & in geosync. transfer (ie 600km x 36,000km), but at
>what altitude do solar / lunar perturbations become too significant for
>reliable predictions to be made? There are some satellites, such as the
>Russian "Granat" & "Astron" astrophysical satellites which are in high
>eccentric orbits with 200,000km apogees, but perigee's of only a few
>thousand km's, so they might be visible in a telescope near perigee.
>However, I'm unsure if SDP4  would be good enough to give an accurate
>prediction (although it might work for a fresh elset on a portion of the
>orbit fairly close to perigee). If not are there any other prediction
>algorithms (eg. HANDE which Skymap can use) which might be up to the
>Best wishes & clear skies,

Along similar lines, at what point do scientists use the "common center of
gravity" of the Earth-Moon system instead of just the center of Earth? I'm
thinking of an object like a probe about to make a gravity assist with Earth?


Harald Schenk