Anthony Ayiomamitis wrote: > How would one go about extracting a satellite's longitude and >latitude from the TLE's? I realize that this will be a function of time >but my question is restricted to geosats and, therefore, time as a >confounding variable should be immaterial. I realize that geosats >experience very small perturbations in their orbits but this is >something I can live with (for now). Don't underestimate the motion of so-called "geostationaries". If they are not exactly at the right orbital altitude they will drift more or or less quickly eastward or westward. However this is not the case for operational satellites. However, many operational satellites have significant orbital inclinations, so they will perform small loops accordingly. You either have to filter these satellites out or you must take time into account so as not to be off-target by several degrees. > I am interested in writing some software to basically parse a >geosat TLE file and produce a list of corresponding longitudes and >latitudes. I would like to produce results, if possible, accurate to >within one and, preferably, two decimal places. This software exists already and is almost exclusively based on the NORAD SGP4/SDP4 algorithms. Whilst the SGP4 algorithm, applicable to LEO objects, yields very accurate results, SDP4 is flawed. It cannot predict accurately the daily loops. But in general it is capable of predicting the location of a geosat so that it can be found with a telescope. > I am setting the stage for a mini-project involving the >photography of geosat constellations and would like to be able to >generate the above-mentioned results at a whim's notice so as to plan my >photo sessions and photo composition/framing. If I interpret your e-mail address correctly, you are located in Greece. You will be able to see two ASTRA and one HOTBIRD constellation. For your project you are not so much interested in longitude/latitude but in azimuth/elevation. If you want to get an impression of what can be done photographing geosats with a CCD camera through a telescope, I suggest you have a look at http://www.astroinfo.ch/aida/sposetti. I have made all the calculations necessary to obtain these photos and to interpret them. Bruno Tilgner Saint-Cloud, France bruno_tilgner@compuserve.com ----------------------------------------------------------------- Unsubscribe from SeeSat-L by sending a message with 'unsubscribe' in the SUBJECT to SeeSat-L-request@lists.satellite.eu.org http://www2.satellite.eu.org/seesat/seesatindex.html
This archive was generated by hypermail 2b29 : Sun May 27 2001 - 13:38:10 PDT