FILTERING METHODS FOR THE ORBIT DETERMINATION OF A TETHERED SATELLITE

The motion of a tethered satellite is affected by a force exerted on t he satellite via the tether. This tether force causes the satellite to experience modified Keplerian motion. Current satellite tracking meth ods do not account for the modified Keplerian motion of tethered satel lites and may result in inaccurate prediction of a tethered satellite' s trajectory. In order to distinguish between Keplerian and modified K eplerian motion, the performance of a batch-type filter was evaluated using a variety of state vectors in order to determine the best possib le estimation model. Eight different state vectors were evaluated, and those determined to most accurately distinguish between the two types of motion were then used to calculate the length of the tether. Three of the eight models were determined to adequately differentiate betwe en Keplerian ant modified Keplerian motion. However, only one state ve ctor was found to provide an accurate calculation of the tether length .