Orbit Determination and Prediction of the International Space Station

The International Space Station is equipped with Global Positioning System receivers that provide real-time position information at the 10m accuracy level. In preparation of the Atomic Clock Ensemble in Space experiment, measurements from Russian and American receivers have been used to assess the navigation accuracy that can be achieved through postprocessing of navigation solutions and raw data in a precise orbit determination process. In addition, the capability to accurately forecast the space station orbit for operation of microwave and laser terminals has been studied. It is shown that the orbit can be reconstructed with a 1 m position accuracy and a 1 mm/s velocity accuracy even from single-frequency Global Positioning System measurements. For the test period in mid 2006, short arc orbit predictions with a median error of 20 and 70 m could be obtained over forecast intervals of 6 and 12 h, respectively. The navigation accuracy obtained is compatible with the mission requirements for the relativistic correction of the atomic clocks and the quick look clock performance monitoring