## 1 Introduction  
The HY-2B/2C/2D satellite constellation is a crucial component of China's marine dynamic environmental monitoring program. Since the successful launch of the HY-2 Dsatellite on 19 May 2021, the three satellites (HY-2B, HY-2C, and HY-2D) have collectively formed China's first marine dynamic environmental satellite monitoring network. With this satellite constellation, the global ocean observation cycle has been reduced from over 20 days for a single satellite to just 6 h, achieving a coverage capacity of more than 80% for global ocean monitoring. This has significantly enhanced the timeliness and accuracy of ocean monitoring [1]. The network is capable of simultaneously retrieving multiple high-temporal-resolution marine dynamic environmental parameters, such as sea surface wind fields, wave heights, sea surface heights, and sea surface temperatures, establishing a comprehensive observation system for all-weather, all-time, and global ocean efficient detection [2]. The satellite constellation not only improves observational capabilities but also enhances data diversity and high precision. The HY-2 series satellites are equipped with advanced instruments such as microwave scatterometers and radar altimeters for collecting critical marine environmental data. They are also equipped with DORIS receivers [3], laser reflector arrays [4], and the independently developed 'HY2_Receiver' onboard GPS receiver to ensure precise orbit determination. The high-precision orbit data obtained via the GNSS receiver supports precise satellite orbit control and enables gravity field model inversion, further advancing research in ocean dynamics and climate change [5]. Additionally, the satellite constellation has the capability for polar and oceanic observations, with sun-synchronous orbits ensuring polar marine environment monitoring and non-sun-synchronous orbits effectively separating tidal components to address tidal aliasing issues. Through constellation-based observation, the variety of satellite data products has been enriched, further enhancing the application efficiency in China's coastal regions and providing essential support for the development of high-resolution regional marine dynamic environmental data products. The use of satellite-borne GPS receivers for precise orbit determination has been integral to satellite missions since the successful POD experiment using GPS data from the Topex/Poseidon satellite in 1992 [6]. These GPS receivers have been deployed on multiple low-Earth-orbit (LEO) satellites, and owing to their advantages of high precision, all-weather operability, and continuous data acquisition, they have become the primary technology for determining the precise orbits of LEO satellites [7; 8; 9; 10]. The orbit determination methods employing satellite-borne GPS [11] encompass kinematic, dynamic, and reduced dynamic methods. Among these, the reduced dynamic method effectively harnesses satellite geometric observations and dynamic model information. It compensates for dynamic model limitations by employing pseudo-random pulse parameters, making it the most widely adopted method for the orbit determination of LEO satellites [12]. Recent research by [PERSON] et al. [13] identified potential periodicity in empirical acceleration for HY-2B, leading to an improved empirical acceleration model. [PERSON] et al. [7] introduced a novel method for verifying orbit accuracy using DORIS data, with the results indicating an external validation accuracy of 6.3 mm/s for HY-2C reduced-dynamic (RD) orbits. The quality of satellite data is a critical factor impacting precise orbit determination and serves as a key benchmark for assessing receiver quality [14]. In theory, observation data errors should manifest as noise sequences with small variances and zero means. However, actual GPS data incorporates unmodeled errors, which can significantly influence orbit determination results.