Satellite Navigation (Jun 2023)
Estimation of BDS pseudorange biases with high temporal resolution: feasibility, affecting factors, and necessity
Abstract
Abstract A common practice adopted for the pseudorange bias estimation and calibration assumes that Global Navigation Satellite System satellite-dependent pseudorange biases vary gently over time. Whereupon satellite pseudorange biases are routinely estimated and provided as the products with low temporal resolution, e.g., hourly or daily, by the agencies. The story sounds unquestionably perfect under the acquainted assumption. To validate the inadequacy of the above hypothesis we herein present an approach to the estimate the BeiDou Navigation Satellite System (BDS) pseudorange biases with high temporal resolution. Its feasibility, affecting factors, and necessity are discussed. Concretely, the Geometry-Free function models are first constructed to retrieve the linear combination of the pseudorange biases; then the pseudorange Observable-specific Signal Bias (OSB) values with respect to baseline frequencies (e.g., BDS C2I/C6I) are estimated along with the ionosphere modeling; subsequently, all multi-frequency pseudorange OSBs are determined by using the ionospheric information with constraint conditions; finally, the possible Differential Code Bias sets are attainable with the estimated pseudorange OSBs. Using the observation data of four months when the estimated BDS pseudorange biases are stable, their reliability is demonstrated with the stability at the level of sub-nanosecond and the BeiDou-3 Navigation Satellite System (BDS-3) values more stable than that of BeiDou-2 Navigation Satellite System (BDS-2). The comparison between the estimated pseudorange biases and the Chinese Academy of Sciences products reveals that the accuracy of the estimated pseudorange biases is 0.2–0.4 ns. Moreover, the large magnitude of the short-term pseudorange bias variation in the tens of nanoseconds for the BDS-2 and BDS-3 are found in years 2021 and 2022, which are affected by two types of the satellite flex power for the BDS-2 and BDS-3, respectively. We stress that it’s necessary to estimate the BDS pseudorange biases with high temporal resolution in the case of the satellite flex power and the products currently provided by the agencies cannot reflect the true quantity under the circumstance.
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