Refinement of Tropospheric Delay Modeling in Satellite Laser Ranging via Atmospheric Ray Tracing Technique

Abstract Tropospheric delay is a major source of error in Satellite Laser Ranging (SLR) observations. The most typical correction method uses the zenith tropospheric delay combined with mapping functions, such as FCULa. Nevertheless, these functions often fail to accurately represent actual tropospheric delays of satellite laser ranging at low elevation angles, leading to systematic errors. Ray tracing, based on the principles of geometric optics, has been extensively studied in global navigation satellite systems (GNSS) and very long baseline interferometry (VLBI), where it has been shown to achieve higher accuracy in tropospheric delay estimation. However, its application in SLR and their evaluation remain insufficient. This study aims to improve tropospheric delay modeling in SLR by comprehensively assessing the accuracy and effectiveness of ray tracing methods and mapping functions. Meanwhile, the coefficients of the recommended FCULa model is recalibrated using high‐precision ray tracing results. Results show that the 3D ray tracing method with ERA5 outperforms mapping functions overall, reducing errors by about 1 mm and improving accuracy by 2%–10%. The improvement is more significant at low elevation angles, where errors decrease by 2–3 mm, corresponding to a 4%–15% enhancement. When used in parameter estimation, ray tracing reduces station coordinate dispersion by about 5.2% on average and improves external consistency with GNSS–SLR local ties by 7%–12%. After calibrating the FCULa model parameters with 3D ray tracing results, the model's accuracy at low elevation angles improves by 1%–7%. This provides a new potential approach for precise tropospheric delay estimation in SLR.