+For GLONASS satellites, that APC/CoM offset is rotated into the satellite-fixed frame using the satellite's +yaw attitude. BNC assumes the nominal Sun-pointing yaw-steering law used for the other GNSS systems, except +close to the orbit noon and midnight points when the Sun's elevation above the orbital plane (the 'beta' +angle) is small. There, GLONASS-M satellites are known to stop tracking that law and instead hold the yaw +angle fixed, following the model described in Dilssner, Springer, Flohrer, Dow (2011), 'The GLONASS-M +satellite yaw-attitude model', Advances in Space Research 47(1), 160-171. Without that correction, the +converted GLONASS CoM position can be off by several decimeters in the along-track and cross-track +components in that situation. The maximum yaw rate used to decide when GLONASS-M can no longer follow the +nominal law (0.25 deg/s) is taken from the literature and not calibrated against any specific satellite, so +results should be checked against independently known attitude or orbit information where high accuracy on +GLONASS is required. +
+Note that clocks in the SP3 orbit files are not corrected for the conventional periodic relativistic effect.