The script in these pages is experimental. The results might not always be accurate!

If the results are doubtful you can use the TLE file http://www.golombek.com/sat/sane.txt. In this file the satellite name is followed by its nominal longitude.

Known Limitations:

• The atmospheric drag is not taken into account. It should not be used for LEOs and current TLE files should be used.

Possible problems:

• There might be a problem around the date of the change to Daylight Saving Time that manifest itself as a 15° shift in the longitude of the sub-satellite point. (15° is the arc the earth rotates in one hour).
• The php getdate() function deals with the extra days in leap years. This works for the long term but I believe that the accuracy of the model degrades by 1/4 of a day each year until it gets fixed every 4 years (much like our own calendar). But since this "time slip" should affect both the satellite location and the translation of axes from Right Ascension to Long. and Lat. it should not affect the calculations for GEO satellites.
• The time used is always the server's local time (UTC -8:00).

this script is based on PLAN-13 by James Miller.

More about this site coming soon.