Orbit, clock and attitude analysis of QZS-1R

More than ten years after the launch of the first satellite of the Japanese Quasi-Zenith Satellite System (QZSS), a replenishment satellite for this spacecraft was launched into inclined geo-synchronous orbit (IGSO) in October 2021. Triple-frequency signal transmission of QZS-1R started on November 14, 2021. In the same month, Cabinet Office, Government of Japan published satellite metadata of QZS-1R including mass, center of mass coordinates, laser retro-reflector offsets, satellite antenna phase center offsets and variations, transmit power, attitude law, as well as spacecraft dimensions and optical properties.

Precise orbit and clock parameters of QZS-1R are estimated with the NAPEOS software. The performance of a box-wing model derived from the satellite metadata is evaluated by day boundary discontinuities, orbit overlaps as well as Satellite Laser Ranging residuals. The analysis of the QZS-1R clock parameters estimated together with the orbits is complemented by a one-way carrier phase clock analysis of selected GNSS receivers connected to highly stable clocks in order to study also the short-term clock behavior.

Like previous QZSS IGSO satellites, QZS-1R transmits the L1 Sub-meter Level Augmentation Service (SLAS) via a dedicated antenna separated about 1.2 m from the main navigation antenna. Therefore, simultaneous observations of, e.g., the L1C/A and the L1 SLAS signals allow to determine the QZS-1R attitude. Attitude estimates from a regional network of eight stations are presented and compared to the nominal attitude of the spacecraft.