Simulation for SLR space segment development to improve global geodetic parameters - different inclination angles & altitudes

Further development of the Satellite Laser Ranging (SLR) technique is essential not only to achieve the goals defined by the Global Geodetic Observing System (GGOS) but also to meet the growing challenges associated with understanding the increasingly frequent and dynamic processes occurring at the Earth's surface. SLR plays a key role in the realization of the Terrestrial Reference Frames (TRFs). It is also crucial for determining the gravitational potential, as the C₂₀ and C₃₀ coefficients in solutions from dedicated GRACE Follow-On missions are replaced by those derived from laser observations.

This study investigates the optimal orbital parameters to consider for future geodetic satellites. We performed simulations for satellites with different inclination angles ranging from 0° to 180° with 1° interval, and at five different altitudes ranging from 1,500 km to 10,300 km with 1,200 km interval. The analysis was carried out under two different scenarios: (1) optimisation for TRF realisation and (2) optimisation for recovery of the Earth's gravitational potential. The results indicate that the optimal satellite altitude for TRF implementation is about 3,700 km, with inclination angles between 0°-20° or 160°-180°, which minimises formal errors in the determination of geocenter coordinates and Earth Rotation Parameters (ERP). On the other hand, geodetic satellites designed primarily to determine the parameters of the Earth's low gravity potential should operate at an altitude of 1,500 km with inclinations between 30°-40° or 135°-145°.

In particular, none of the current satellites in the SLR constellation have orbital parameters optimised for low-degree gravity recovery. Adding a single satellite with suitable inclination parameters to the existing constellation of ten geodetic satellites would reduce the error in the determination of the Earth's oblateness term, C₂₀, by order of magnitude.