172 / 2023-08-31 01:36:21

Assessment of multiple ambiguity resolution methods in LEO precision orbit determination

Ambiguity resolution,Precise orbit determination,LEO,Orbit accuracy,Fixing rate

Ambiguity resolution (AR) is an effective method to improve the orbit accuracy of Low Earth Orbit (LEO) precise orbit determination (POD). The most commonly used single-difference (SD) ambiguity resolution (AR) requires phase fractional biases of GNSS satellites, and several organizations have released phase fractional bias products, including the uncalibrated phase delay (UPD), the observable-specific biases (OSB) and the integer recovery clocks (IRC). This study performs SD AR based on various products, and analyzes the AR performance using various products. In addition, for cases such as new satellites where the bias products cannot be obtained in time, track to track (T2T) and single-difference track to track (SDT2T) are needed as alternative for AR. However, these two methods ignore the difference of phase fractional biases between arcs, so an iterative scheme based on the time interval between arcs is needed to improve these two AR methods, and eliminate the effect of the difference of phase fractional biases between arcs on AR as much as possible. In this study, the SD based on various bias products, T2T and SDT2T AR methods are used to GRACE-C POD. The results show that there is no significant difference in SD AR performance employed various products, and only OSB products have slightly better orbit accuracy and fixing rate than other products. The orbit accuracy of the T2T AR cannot reach the same level as that of SD AR, mainly due to ignoring of the difference of the narrow-lane (NL) phase fractional biases of the satellites and the receivers between arcs, and it cannot be used as a good alternative to SD AR. The SDT2T AR eliminates the receiver phase fractional biases and only ignores the difference of the satellite NL phase fractional biases between arcs. Because the satellite NL phase fractional biases is essentially stable in one day, the orbit accuracy of the method is better than that of the T2T method, and there is no significant difference in the orbit accuracy of the SD AR method, which is even better than that of SD AR using the UPD and IRC products. The SDT2T method does not need phase fractional bias products, which makes it an effective AR method.