Impact of non-gravitational force model deficiencies for Genesis orbit and geodetic parameter estimation based on GNSS

Abstract

The ESA Genesis mission, which obtained green light at ESA's Council Meeting at Ministerial Level in November 2022 and which is expected to be launched in 2028, aims to significantly enhance the accuracy and stability of the Terrestrial Reference Frame (TRF). This shall be achieved by equipping one satellite at approximately 6000 km altitude with well-calibrated instruments for all four space-geodetic techniques contributing to TRF realizations, i.e., Global Navigation Satellite Systems (GNSS), Satellite Laser Ranging (SLR), Very Long Baseline Interferometry (VLBI) and Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS), and by exploiting the such realized very precise space co-locations.

For Genesis to provide a strong contribution to any reference frame realization, a dynamic satellite orbit modeling is a prerequisite, as empirical orbit parameters might correlate significantly with specific geodetic parameters. Therefore, a detailed explicit modeling of non-gravitational forces is needed, including a proper description of the satellite geometry and optical properties (macro model).

This study focuses on uncertainties of Genesis macro model quantities and aims to assess their impact on GNSS-based POD of Genesis, as well as GNSS-based global network solutions including data from ground stations and Genesis. In particular, the effect is studied for the estimation of GNSS orbits and clock corrections, Earth rotation and geocenter parameters and station coordinates. To accomplish this, we employ simulated GNSS pseudo-range and carrier phase data for Genesis and an extended set of IGS ground stations, which have been generated based on detailed link-budget computations and a comprehensive set of transmit antenna gain patterns. The data are used for closed-loop simulation investigations, where, in the reconstruction step, we systematically change Genesis macro model properties. Comparison of the reconstructed orbit and geodetic parameter solutions to the simulation truth offers a quantification of the impact of these errors on the estimated parameters. We study 37 days in 2023, covering an entire cycle of Sun-orbital plane geometries of the considered Genesis orbit, and present the impact of the macro model uncertainties on the recovered solution for the entire time span.