Static and dynamic models of observation toward earth by satellite coverage

In satellite mission planning in order to observe area targets, it is needed to decompose area targets into small pieces and compute visible time windows for sub-area targets. Therefore, it is expected to compute geodetic location of ground target observed or to compute observing time by satellite with some certain sensing actions, such as slew-looking. This paper presents static and dynamic models of observing ground targets by satellite for above two problems respectively. The static model is to compute the geodetic location coordinates at which boresight of sensor with a certain roll angle is pointing. Furthermore a reverse model, to be used in dynamic model, is derived from the static model to compute subsatellite point (SSP) if roll angle and target location are known. Then, the dynamic model is designed to determine the observing SSP and roll angle if target location is known. The observing SSP corresponds to observing time, and roll angle is sensing action for slew-looking. The dynamic model use the reverse model developed from the static model to compute virtual SSPs according to a series of rolls, and then get intersection point of virtual SSPs and real SSPs by prediction. During dynamic model development, it is proved that the closest point of SSPs to the ground point is not always the demanded SSP. Finally experiments are presented and compared with results by Satellite Tool Kit (STK) to verify proposed models.