Orbit determination analysis of IGSO satellite onboard GPS/BDS pseudorange data corrected by different code hardware delays products

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The navigation signal received by the Inclined Geo-Synchronous Orbit (IGSO) satellite is often blocked by the Earth, and the signal strength is weak due to the long propagation distance, which makes the carrier phase data processing complicated. Using pseudorange data is a convenient and efficient method for determining the orbit of IGSO satellites. Code hardware delays are non-negligible errors in pseudorange data processing. This study investigates the precise orbit determination (POD) result using only pseudorange data corrected by four types of Differential Code Bias (DCB) products and Observable-specific Signal Biases (OSB) products, with the LT4A satellite as a case study. The results show that the correction of code hardware delay can effectively improve the orbit quality. After correcting the code hardware delay, using only GPS pseudorange observations, using only BDS pseudorange observations, and using GPS + BDS combined pseudorange observations to determine the orbit, the pseudorange residuals RMS are about 1.82 m, 1.09 m, and 1.53 m, respectively. Compared with the uncorrected code hardware delays results, the residuals RMS is better by 21.8 %, 79.5 %, and 53.0 %, respectively. As the length of the POD arc increases from 24 h to 72 h, both the quality and stability of the orbit are observed to improve. For the 72 h arc, the orbit overlap RMS with the three data types is 3.4 m, 3.0 m, and 2.8 m, respectively, with the improvement of about 10.5 %, 77.6 %, and 59.4 %, respectively, compared with no code hardware delays correction. Compared with the precise reference orbit, the comparison RMS are 6.3 m, 4.8 m, and 4.4 m, increased by 24.0 %, 78.9 %, and 51.6 %, respectively. The results demonstrate that the comparison RMS of the IGSO satellite with only pseudorange data can be better than 5 m in position, and correcting the code hardware delays can improve orbit quality obviously, especially for BDS pseudorange data.