Phase Center Offset and Phase Center Variation Estimation In-flight for ZY-3 01 and ZY-3 02 Spaceborne GPS Antennas and the Influence on Precision Orbit Determination

ZY-3 01 and ZY-3 02 satellites, as important remote sensing stereoscopic mapping satellites in China, undertake the tasks of production of geographic products, land resource investigation and so on. Precision orbit determination(POD) is a prerequisite for the success of ZY-3 01 and ZY-3 02 missions. Dual-frequency GPS receiver and SLR reflector manufactured by China play significant roles in POD and independent orbits checkout. Although PCO priori values were obtained before satellites launched,by PCO estimation in-flight, this paper analyses the feasibility of PCO in different directions and finds ZY-3 01 and ZY-3 02 SLR RMS checkouts are improved 0.331 mm,0.399 mm respectively. Further, this paper estimates PCV models of ZY-3 01 and ZY-3 02 spaceborne GPS antennas using direct approach and residual approach and their PCV models can reach[-15 mm 15 mm]. Through the use of PCV models(10°×10°), ZY-3 01 orbits SLR checkouts are improved 2.143 mm (direct approach), 1.628 mm (residual approach), orbit accuracy in 3D of overlapping arcs are improved 11.377 mm (direct approach),13.903 mm (residual approach), ZY-3 02 orbits SLR checkouts are improved 0.727 mm (direct approach),0.692 mm (residual approach), orbit accuracy in 3D of overlapping arcs are improved 1.736 mm (direct approach),1.548 mm(residual approach).The effect of PCV model resolution (10°×10°,5°×5°,2°×2°) on POD is further discussed in this paper. After comprehensive consideration of computational efficiency, storage space, increase amplitude and other factors, 5°×5° PCV model by residual approach is the best choice