Comparisons of NORAD two-line elements with INTELSAT orbital elements

We have compared the publicly accessible NORAD Two-Line Elements (TLE) provided by the US Air Force with the INTELSAT proprietary orbital elements derived from our dual station ranging system. The comparisons were performed for the INTELSAT fleet of geosynchronous satellites, which are distributed over three ocean regions, for a one-year time span. INTELSAT undertook these comparisons to assess the reliabilities of using NORAD TLE for conjunction detection analysis. The objectives of these comparisons are: (1) To study the time history of the differences of the TLE and INTELSAT orbital elements in order to analyze the temporal variations in the TLE; (2) To study the differences of the TLE and INTELSAT orbital elements by ocean regions in order to analyze the spatial variations in the TLE; (3) To study degradation in the TLE accuracy within the update intervals due to the scheduled maneuvers and the accuracy of the TLE at update epoch.