Abstract
The real-time integer-ambiguity resolution of the carrier-phase observation is one of the most effective approaches to enhance the accuracy of real-time precise point positioning (PPP), kinematic precise orbit determination (KPOD), and reduced-dynamic precise orbit determination (RPOD) for low earth orbit (LEO) satellites. In this study, the integer phase clock (IPC) and wide-lane satellite bias (WSB) products from CNES (Centre National d’Etudes Spatiales) are used to fix ambiguity in real time. Meanwhile, the three models of real-time PPP, KPOD, and RPOD are applied to validate the contribution of ambiguity resolution. Experimental results show that (1) the average positioning accuracy of IGS stations for ambiguity-fixed solutions is improved from about 7.14 to 5.91 cm, with an improvement of around 17% compared to the real-time float PPP solutions, with enhancement in the east-west direction particularly significant, with an improvement of about 29%; (2) the average accuracy of the estimated LEO orbit with ambiguity-fixed solutions in the real-time KPOD and RPOD mode is improved by about 16% and 10%, respectively, with respect to the corresponding mode with the ambiguity-float solutions; (3) the performance of real-time LEO RPOD is better than that of the corresponding KPOD, regardless of fixed- or float-ambiguity solutions. Moreover, the average ambiguity-fixed ratio can reach more than 90% in real-time PPP, KPOD, and RPOD.
Highlights
The applications of low earth orbit (LEO) satellite data are successfully and widely demonstrated in various areas, such as remote sensing [1,2], communications [3,4], atmospheric sounding [5,6], radio occultation [7,8], ocean altimetry [9,10], and so on
Experimental results show that (1) the average positioning accuracy of International global navigation satellite systems (GNSS) Service (IGS) stations for ambiguity-fixed solutions is improved from about 7.14 to 5.91 cm, with an improvement of around 17% compared to the real-time float precise point positioning (PPP) solutions, with enhancement in the east-west direction significant, with an improvement of about 29%; (2) the average accuracy of the estimated LEO orbit with ambiguity-fixed solutions in the real-time kinematic precise orbit determination (KPOD) and reduced-dynamic precise orbit determination (RPOD) mode is improved by about 16% and 10%, respectively, with respect to the corresponding mode with the ambiguity-float solutions; (3) the performance of real-time LEO RPOD is better than that of the corresponding KPOD, regardless of fixed- or float-ambiguity solutions
Validation Results of Real-Time Ambiguity Resolution for LEO RPOD the real-time RPOD is computed for GRACE satellites by employing the ambiguity-fixed and ambiguity-float solution to verify the performance of LEO precise orbit determination (POD)
Summary
The applications of low earth orbit (LEO) satellite data are successfully and widely demonstrated in various areas, such as remote sensing [1,2], communications [3,4], atmospheric sounding [5,6], radio occultation [7,8], ocean altimetry [9,10], and so on. To meet the growing needs for real-time spaceborne missions, such as LEO-enhanced real-time location service [11] and real-time atmospheric sounding [12], it is necessary to obtain precise orbits of LEO satellites in real time. It is reported that 7 cm-accuracy kinematic LEO POD can be obtained in real-time mode from the Fugro G4 SSR products based on Swarm-C onboard observations [15]. The BeiDou navigation satellite system (BDS-3) precise point positioning (PPP) service of China [16,17], the new generation of the Australian/New Zealand (AU/NZ) satellite-based augmentation systems (SBAS)-aided PPP service [18], the Quasi-Zenith Satellite System (QZSS) of Japan [18,19], and Galileo’s high-precision PPP service in Europe [20] have their own way to provide real-time GNSS orbit and clock products for users. It is expected that the abovementioned real-time high-precision services will assist spaceborne missions that need precise orbital information
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