IGS GNSS satellite phase bias products: quality assessment and applications

As part of the International GNSS Service (IGS), several analysis centers (i.e., CODE, CNES/CLS, GFZ, WUHN) provide GNSS (GPS, Galileo, BeiDou) satellite phase bias products to support precise point positioning with ambiguity resolution (PPP-AR). Due to the high correlation with satellite orbits and clock offsets, it is difficult to assess directly the precision of satellite phase bias products. The commonly used approach is to check the positioning performance in PPP-AR applications. However, errors or outliers in phase bias of a specific satellite are not directly visible in this process but lumped into the overall observation residuals. This contribution presents a method independent of ground measurements to detect outliers in satellite phase biases by computing the total Difference of satellite Orbits, Clock offsets and narrow-lane Biases (DOCB) at the midnight epoch between two consecutive days. This method can be also used to assess the consistency of satellite products between two different analysis centers. It is convincing that after removing the detected outliers in individual analysis centers the number of large differences of satellite phase biases between two analysis centers is notably reduced. To show the impact on PPP-AR, we generate a list marking all the outliers in the phase bias products from individual analysis centers, and evaluate the performance in ground-station kinematic positioning and Sentinel-6 satellite orbit determination.