Updated radiation pressure force modeling and validation: case studies for GRACE and Sentinel-6 MF

Abstract Highly accurate radiation pressure (RP) force modeling is required for precise orbit determination, gravity field recovery, and thermosphere density retrieval. For radar altimetry missions, especially the radial component is important, and validating RP force models in general is still challenging. In this study, we focus on the precise modeling and validation of RP forces for low Earth orbit satellites with given macro-model. We develop a new transient temperature model for Sentinel-6 MF based on thermistor measurements to account for transient heat-conductive re-radiation. The RP force models were applied on Sentinel-6 MF and GRACE-A for a whole year. The choice of different thermal re-radiation pressure (TRP) force models was found to impact the acceleration by up to 20 nm/ $$\hbox {s}^2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mtext>s</mml:mtext> <mml:mn>2</mml:mn> </mml:msup> </mml:math> , which is as large as the average Earth radiation pressure signal in sunlight. We validate RP force models for both satellites with independent satellite laser ranging (SLR) data. For GRACE-A, we found that neglecting TRP modeling is better than using the static model with instantaneous heat re-radiation, since the RMS of SLR residuals increased by 24% when including static TRP. The validation for Sentinel-6 MF with our in-house processing framework revealed that the new TRP model decreases the SLR residuals by 1.4% compared to neglecting TRP and that amplitudes of empirical accelerations significantly decrease by up to 38% on average compared to applying static re-radiation. An additional validation according to the Copernicus POD Service standards confirms the results. Further, we discuss ways to overcome knowledge gaps in existing RP force models in the future.