Research on the Number and Distribution of GPS Occultation Events for Orbit Selection for Global/Regional Observation

The small/micro satellites equipped with spaceborne GPS receivers have been proved suitable platform for GPS radio occultation observation, as they can form a cheap network for global atmosphere observation. The quality of GPS radio occultation observation varies with the orbit chosen for the LEO satellite. As a result, the impact of the orbit on the observation quality should be studied. For this purpose, this paper develops an occultation events simulation system, in which positions of small/micro observation satellite and GPS satellites at different time are calculated by SGP4 model and SDP4 model, and then a Matlab program deals with these positions, judges the occurrence of occultation events, taking the field of view of the GPS antenna into account, calculates the longitude and latitude of the spot and also the duration of the occultation events, based on which distribution pictures can be drawn. With the system, two topics have been discussed: simulation for satellites with different orbit parameters, and the impact of each parameter on the number and distribution of occultation events. With these rules, the optimized orbits for global GPS radio occultation observation or observation of a certain region can be designed.