An Evaluation of Solar Radiation Pressure Models for QZS-1 Precise Orbit Determination

S. Ikari, T. Ebinuma, R. Funase, S. Nakasuka

Abstract:	QZS-1 (Michibiki) is the first satellite of Japanese Quasi-Zenith Satellite System (QZSS) launched in September 2010. QZSS provides regional navigation services interoperable with GPS in Asia and the Pacific. Precise orbit and clock information of the QZSS and other navigation satellites is essential to precise positioning and navigation applications. The Japan Aerospace Exploration Agency (JAXA) has started developing Multi-GNSS Advanced Demonstration tool for Orbit and Clock Analysis (MADOCA) for Global Navigation Satellite Systems (GNSS) including QZSS since 2011(Miyoshi, 2012). Similar to the other GNSS satellites, solar radiation pressure (SRP) is one of the dominant disturbance forces acting on QZS-1, and a reliable SRP modeling is essential for precise orbit determination. The main purpose of this research is to establish a proper strategy of SRP modeling for QZS-1 precise orbit determination. For GPS and GLONASS satellites, various types of SRP models have been studied since 1980s. There are mainly two modeling approaches. First is the physics based modeling approach. This is an analytical model using the shape and optical characteristic of the satellites. For example, the so-called box-wing model assumes that the satellite is a box-shape bus system with two solar panel wings and calculates the SRP from the satellite attitude with respect to the sun. Second is the empirical modeling approach. This model assumes that the SRP of the satellite is defined by the combination of polynomials and periodic functions, and the coefficients of these functions are estimated from long term GNSS observation data. The final orbit determination accuracy achieved by using the empirical model is typically better than that obtained by using the physics based model for GPS and GLONASS, and it is quite possible that the same empirical model works better for QZS-1 as well. First in this study, DBY empirical model (Beutler, 1999) and box-wing model (Marshall, 1994) are adapted for QZS-1 and implemented into MADOCA. To evaluate the difference of these SRP models, a set of orbit determination experiments was conducted using the QZS-1 observation data obtained by the same ground stations. The obit accuracy is derived from 1-day orbit overlaps at day boundaries of 2-day solutions. As a result, an orbit accuracy of 7 cm can be achieved by the DBY empirical model, while the estimation error is around 2 m with the box-wing model. Although the estimation error is rather large, the box-wing result is still compatible with that of GLONASS satellites reported in early work (Ziebart, 2001). It is thought that the larger orbit determination error of the box-wing model is caused by uncertainty in a-priori knowledge of the physical parameters such as the optical properties, the surface area, the attitude or mass of the satellite. In order to identify the most influential model parameter of the QZS-1 satellite, an error sensitivity analysis is performed. The analysis result shows that the uncertainty in reflectivity of the QZS-1 body surface causes the largest orbit error. For example, even 1% error in reflectivity causes about 1.5 m position propagation error during one orbital period. A recently developed SRP model called adjustable box-wing model (Rodoriguez-Solano, 2012) is also applied to QZS-1, and the reflectivity of each satellite surface including solar array panels is estimated simultaneously with the QZS-1 orbit. The result shows that the adjustable box-wing model can improve the orbit determination accuracy to 70 cm. It is better than that of the traditional box-wing case but still worse than the final orbit obtained by DBY empirical model. The interesting point is that the time series of the SRP accelerations obtained by DBY empirical and box-wing models are quite different. Further study on the QZS-1 surface properties and other non-conservative forces is required. Another limitation for the QZS-1 precise orbit determination is a shortage of ground reference stations supporting QZS-1 observations. For the above-mentioned experiments, only five monitoring stations in less favorable geometry are available, while 60 or more global stations are applicable for GPS and GLONASS orbits. This situation will change in the near future since JAXA is now establishing Multi-GNSS Monitoring Network (MGM-Net) under international collaboration as part of Multi-GNSS Demonstration Campaign. At present, 15 stations are operational in Asia and Pacific region (Kogure, 2012), and more QZS-1 observations are expected to be available for public in 2013. More rigorous evaluation and comparison of different SPR models will be conducted once more MGM-Net stations get accessible. References Miyoshi,M., et al, “The orbit and clock estimation result of GPS,GLONASS and QZSS by MADOCA”, The 23rd International Symposium on Space Flight Dynamics, Pasadena Convention Center, October 29 - November 2, 2012 Beutler, G., Brockmann, E., Gurtner, W., et al., “Extended orbit modeling techniques at the CODE processing center of the International GPS Service for Geodynamics (IGS): theory and initial results,” Manuscr Geod, 19 (6), 1994, pp. 367-386. Kogure, S., “The current status of Asia Oceania Multi-GNSS demonstration campaign,” ICG Working Group A, ICG-7 Meeting, Beijing, China, 4-9 November 2012. Marshall, J. A. and Luthcke, S. B., “Modeling Radiation Forces Acting on Topex/Poseidon for Precision Orbit Determination,” J Spacecr Rockets, 31 (1), 1994, pp. 99-105. Rodoriguez-Solano, C., Hugentobler, U., and Steigenberger, P., “Adjustable box-wing model for solar radiation pressure impacting GPS satellites,” Adv Space Res, 49 (7), 2012, pp. 1113-1128. Ziebert, M., “High Precision Analytical Solar Radiation Pressure Modilling for GNSS Spacecraft,” Ph.D. Thesis, University of East London, June 2001.
Published in:	Proceedings of the 26th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2013) September 16 - 20, 2013 Nashville Convention Center, Nashville, Tennessee Nashville, TN
Pages:	1234 - 1241
Cite this article:	Ikari, S., Ebinuma, T., Funase, R., Nakasuka, S., "An Evaluation of Solar Radiation Pressure Models for QZS-1 Precise Orbit Determination," Proceedings of the 26th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2013), Nashville, TN, September 2013, pp. 1234-1241.
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