On the accuracy of the SGP4 to predict stellar occultation events using ENVISAT/GOMOS data and recommendations for the ALTIUS mission

In preparation for the operations of the ALTIUS mission, research is carried out to assess the accuracy of the SGP4 orbital propagator in predicting stellar occultationevents. The quantification of the accuracy and its consequent improvement will enable reliable measurement planning and, therefore, maximize the number of measurements. To this end, predictions are made for the timing of occultationsfor the GOMOS instrument on-board the ENVISAT, which are then compared to actual occultationoccurrences. It is found that the error is substantial but follows a trend that can be interpolated. This enables devising a method for highly accurate predictions given a sufficient number of data points. Statistically significant results for the accuracy of the propagator and a calibration method are presented. Recommendations for a measurement planning procedure of ALTIUS are formulated.