Tsinghua Scientific Satellite Precise Orbit Determination Using Onboard GNSS Observations with Antenna Center Modeling

Abstract

The Tsinghua scientific satellite is a Chinese spherical micro satellite for Earth gravity and atmospheric scientific measurements. The accurate orbits of this satellite are the prerequisites to satisfy the mission objectives. A commercial off-the-shelf dual-frequency GNSS receiver is equipped on the satellite for precise orbit determination (POD). The in-flight performances of the receiver are assessed. Regular long-duration gaps up to 50 min are observed in GNSS data, and the typical data availability is about 60–70% each day. The RMS of code noises is 0.24 m and 0.30 m for C1 and P2 codes, respectively. The RMS of fitting residuals of the carrier phase geometry-free L1–L2 combination is 2.4 mm. The GNSS receiver antenna center offsets (ACOs) and antenna center variations (ACVs) maps are estimated using in-flight data for both dual-frequency and single-frequency POD. Significant improvements in POD performances are obtained when the measurement models are updated by using the ACO and ACV maps’ corrections. With the updated measurement model, the RMS of the orbit overlap differences is 1.23 cm in three dimensions for dual-frequency POD, which is reduced by 27%. Meanwhile, two different empirical acceleration types are employed and compared for dual-frequency POD, and the results show that consistency on the 5 cm level is demonstrated for orbit solutions obtained with the updated measurement model. After correcting the ACO and ACV maps, the precision of single-frequency orbit solutions is better than 10 cm, which is improved by 32%. The results indicate that the antenna center modeling can significantly improve the consistency of Tsinghua scientific satellite precise orbits, which will be conducive to the realization of the mission objectives.

ACP-Based Space Systems: Design, Development, and Operation

“…One example of the applications of Q-Sat parallel systems is to analyze and process in-orbit satellite data, aiming to refine the models within the artificial systems and improve the accuracy of orbit prediction and collision warning in the actual systems. The model parameters within the artificial systems are adjusted using high-precision centimeter-level orbital data from the real Q-Sat system [41,42]. A five-day period, from January 11th to 15th, 2022, is selected, with each 24-hour orbit serving as an adjustment unit.…”

Design and Verification of an Integrated Panoramic Sun Sensor atop a Small Spherical Satellite

“…This paper proposes the development and verification of an integrated panoramic sun sensor that can support satellite attitude determination with full spherical coverage. The background of the research is a spherical satellite called Q-SAT aimed at joint estimation of upper atmospheric density and long-wave gravity field in low-Earth orbit [ 1 , 2 , 3 , 4 , 5 ]. Q-SAT was launched atop the CZ-2D rocket on 6 August 2020, and has been working well for more than two years.…”

“…Q-SAT was launched atop the CZ-2D rocket on 6 August 2020, and has been working well for more than two years. The main payload of Q-SAT is a dual-frequency GNSS receiver, which provides cm-level orbit determination after postprocessing [ 3 ]. The precise orbit is used to inverse the aerodynamic drag force applied to Q-SAT, and thus the upper atmospheric density.…”