LAUSR

Japanese Quasi-Zenith Satellite System (QZSS) consists of three inclined geosynchronous orbit (IGSO) satellites as well as a geostationary satellite. According to the QZSS metadata, the three IGSO satellites are equipped with large L-band antennas, which can be assumed as a combination of a circular cylinder and a circular truncated cone. By using the geometrical and optical properties released by the metadata, maximum accelerations of about 5.0 nm/s 2 , 4.5 nm/s 2 , and 2.2 nm/s 2 can be generated by the side surface of the QZS-1 L-band antenna for the along-track, cross-track, and radial components, respectively. By introducing the so-called box-wing-hat model as an a priori one and estimating parameters of Extended CODE Orbit Model (ECOM), the performances of both precise orbit determination and precise clock estimation can be improved for IGSO satellites. With the a priori box-wing-hat model, the root mean square values of 3D orbit overlapping are 8.5 cm, 27.5 cm, 13.2 cm, and 15.3 cm for QZS-1 in yaw-steering (YS) mode, QZS-1 in orbit-normal mode, QZS-2, and QZS-4, respectively. Satellite laser ranging validation reveals that the standard deviation (STD) values of the a priori box-wing-hat model are 5.6 cm, 5.5 cm, and 5.3 cm for QZS-1 in YS mode, QZS-2, and QZS-4, which are smaller than those of ECOM, ECOM2, and the a priori box-wing model. Regarding the estimated clock offsets, overlapping STD values of smaller than 0.1 ns can be achieved for QZS-1 in YS mode, QZS-2, and QZS-4 by using the a priori box-wing-hat model. Also, the Modified Allan Deviation of the clock estimates can be improved by using the a priori box-wing-hat model for integration time longer than 2000s.