Contribution of intersatellite link measurements to ECOM solar radiation pressure estimation on the BDS-3 MEO satellite

The BDS-3 constellation is equipped with Ka-band intersatellite link (ISL) devices on all its satellites, providing intersatellite ranging capabilities to enhance their orbiting accuracy. However, whether this advantage can be utilized to improve the parameter estimation of BDS-3 solar radiation pressure (SRP) remains uncertain. BDS-3 medium-circular earth orbit (MEO) satellites, developed by the China Academy of Space Technology (CAST) and Shanghai Engineering Center for Microsatellites (SECM), consist of a cuboidal box and solar wings. The presence of the cuboid introduces a sun-satellite-earth angle ε-dependent systematic error that manifests in the estimated orbits using L-band measurements collected by ground stations when applying the empirical SRP model, such as the reduced 5-parameter Extended CODE orbit model (ECOM1) and its modified version (ECOM2). We investigate the contribution of ISL observations to ECOM1 and ECOM2 estimation in precise orbit determination of the two types of MEO satellites, with a specific focus on estimating SRP for the cuboidal satellite body. We analyze the systematic biases in satellite laser ranging (SLR) residuals, acceleration along the sun-satellite direction ( D_0 parameter of ECOM), and orbit prediction accuracy of joint orbit determination employing Ka-/L-band measurements. Surprisingly, the systematic linear trend relative to ε-angle in SLR residuals exhibited a substantial decrease. For the ECOM1 model, the slope of approximately -0.109 cm/° observed in CAST satellites is nearly eliminated, while for the SECM satellite, the slope decreases from 0.056 cm/° to 0.022 cm/°. Regarding the ECOM2 model, the linear trend for both CAST and SECM satellites is nearly eliminated with ISL data. Moreover, the jointly estimated D_0 curves are smoother and closer to the theoretical trend driven by the cuboidal body for both ECOM1 and ECOM2. The improvement in ECOM2 D_0 estimation by ISL is significant for | β |< 40°, since ISLs can improve the correlation between D_0 and the D_s2 , D_c4 , D_s4 , B_0 , B_c1 , and B_s1 parameters. The experiment further suggests that ISLs established by satellites in different orbital planes make a greater contribution to SRP estimation than ISLs established by satellites in the same orbital planes. In addition, the 1-day orbit prediction is used to indirectly evaluate the re-estimated ECOM parameters. The 3D prediction accuracy of both ECOM1 and ECOM2 improves by more than 50