Multi-Observations Initial Orbit Determination based on Angle-Only Measurements

A new approach with the ability to use the multiple observations based on the least square approach has been proposed for initial orbit determination. This approach considers the Earth’s Oblateness by using the developed Lagrange coefficients. The efficiency of the proposed method has been tested in two scenarios. The first scenario is to use the simulated and the second one is to utilize the real angle-only observations for the GRACE-like and GPS-like satellites. Under the first scenario, the ground-based observations are produced using the reduced-dynamic orbit generated by GFZ. Then, various error levels were added to the produced azimuth and elevation observations. The results show that considering the Earth’s oblateness could improve the accuracy of the initial orbit determination by six times for a GRACE-like satellite, and by 60 times for a GPS-like satellite. Afterward, under the second scenario, the real observations of the SLR station were used. In view of increasing in the number of observation tests, by increasing the numbers of the observations from 3 to 15, the accuracy of initial orbit determination was improved from 1496 to 8 m using the SLR data for the GRACE-A satellite.