Fast Algorithm for Prediction of Satellite Imaging and Communication Opportunities

Abstract

A new equation for nadir tracking estimation, taking into account secular perturbations from the Earth’ s gravitational e eld and the ine uence of drag, is presented. The advantage of this proposed approach is that it needs to be solved just twice per day with respect to a specie c ground target (there are usually 14 orbital periods per day for sun synchronous orbit ). The resultant approximate near nadir angle time, whose root of mean square error is around a fewseconds (i.e.,» 30-km groundtrack error ), isthen further ree ned using a newly developed controlling equation, reducing the maximum error to about 0.4 s (» 2:8 km groundtrack ) for over 20 days prediction period. This is acceptable when the imaging e eld of view of 10 km is considered for high resolution small satellite cameras. Thepredictionperiod of 60 dayscan beusedfora typicalsmall satellitecamerawhosee eldofviewisabout100 km. This method can also be expanded to solve the rise-and-set time problem. Because of the low complexity of the proposed method, it is very suitable for implementation on the onboard processor whose computational resources are generally limited. The new computational process is described and simulation results are presented. Nomenclature