Two-site orbit determination: The 2003 GEO observation campaign from Collepardo and Mallorca

In September 2003 the Group of Astrodynamics of the University of Rome “La Sapienza” (GAUSS) carried out a two-site optical observation campaign devoted to the autonomous orbit determination of objects in the geosynchronous region. Two 40 cm aperture Ritchey-Chrétien devices were employed: the f/7.5 “Collepardo Automatic Telescope” (CAT, located in Collepardo, Italy) and a f/5 tube of the “Observatori Astronòmic de Mallorca” (OAM, located in Mallorca, Spain). The baseline between the sites is 963 km. 3 s long, 1 minute apart exposures were simultaneously taken in sidereal tracking mode, looking at the same arcs of the GEO ring; the fields of view allowed to see a few satellites in two successive frames from both sites. To determining the orbits the Lambert theorem has been exploited, improved with the least square method by chance that more than 2 points were available. Of course, the longer the time interval between positions, the lower the effect of measurements errors. Nevertheless, the only way to have quite distant points would be tracking the satellite, which is typically not suitable for a surveillance campaign, thus not very interesting from a practical standpoint. In the paper the results of the orbit determination from the September 2003 campaign are reported. More in detail, the outcomes of some classical methods for solving the Lambert theorem, are compared with the least squares improved solutions, with the circular orbit assumption results, with the one-site complete orbit determination and with the TLEs.