Improved Yaw Model Enhances GPS Block IIF Satellite Performance During Eclipse Seasons
A recent study published in Satellite Navigation has introduced an improved yaw model for Global Positioning System (GPS) Block IIF satellites, specifically designed to address attitude and clock estimates during eclipse seasons. The new model, developed by a research team at Wuhan University and collaborating institutions, utilizes Reverse Kinematic Precise Point Positioning (RKPPP) estimates from 7.5 years of global tracking data to improve the representation of GPS Block IIF satellite yaw during eclipse-season maneuvers.
The study focused on addressing recurring mismatches in rotation direction, maneuver onset timing, and pre-eclipse yaw evolution, which can lead to biased satellite clocks and phase biases. The researchers introduced satellite-specific beta-angle (β-angle) biases and a small-angle midnight-turn decision rule to refine the model. When tested in network orbit and clock estimation, the revised model reduced attitude-related phase-residual signatures and produced smoother satellite clock estimates around yaw turns.
The improved model targets noon- and midnight-turn discrepancies, which can propagate into phase residuals and satellite clock offsets. The analysis found four recurring discrepancies, including a mismatch in rotation direction, abrupt rotation-direction changes at maneuver onset, and maximum yaw differences above 40°. The revised model resolved these issues by introducing satellite-specific β thresholds and a modified β angle before eclipse entry.
The study's findings support more consistent precise positioning and timing, essential for Global Navigation Satellite System (GNSS) precise orbit determination (POD), clock estimation, signal-bias modeling, and precise point positioning (PPP). The research highlights the value of observation-driven approaches for assessing and refining GNSS satellite attitude models, especially when manufacturer attitude-control details are limited.
