Other On-Screen Parameters

This options allows the date of the orbit calculation to be specified. To do this, move the highlighted bar over the date displayed and press Enter to choose a new date. The default date is set in the ground.par parameter file, under the epoch of orbital elements.

Note that once a new value is entered the values of , the Longitude of the ascending node and , the argument of perigee will take on slightly new values. This is due to the fact that this program incorporates a routine which takes some orbit evolution effects into account. This routine performs a first order calculation of the orbit evolution based upon the J2 coefficent of the Earth's gravitational potential. This correction is not highly accurate and the cumulative errors will build up as the difference between the launch date and the observation date considered becomes large.