Single-Differenced Ambiguity Resolution for Orbit Determination of the Haiyang-2B

In ambiguity resolution, the Hatch–Melbourne–Wubbena code and carrier phase combination is usually used to fix the wide-lane (WL) ambiguity, and thus, the quality of the code observations directly affects the fixing success rate, especially when there are some kind of serious bias errors. Unfortunately, we found that the P1 code multipath (MP) errors of the Haiyang-2B calculated using the MP combination formula rapidly increases from sub-meter to several meters at elevation less than 40°. These rapid variations lead to biases in the fixed WL ambiguities. In this article, we create a static correction map on a grid with 5° x 5° resolution. Using this correction map, we reduced the root mean square of the P1 code bias errors from 1.04 to 0.47 m, which corresponds to an improvement of 54.8%. By comparing the different precise orbit determination solutions, we found that the ambiguity resolution significantly reduced the satellite laser ranging (SLR) residuals from 1.63 to 1.31 cm with an average improvement of 19.6%. However, because of the code errors, the ambiguity fixing rate of the P1 ambiguity-fixed solutions was much lower than that of the C1 solutions. By modeling this static correction, the impact of these errors was effectively reduced. The ambiguity fixing rate for the P1 solutions was improved by 15.6% and a 1–3 mm reduction in the SLR residuals was small but noticeable.