Application of TWSTFT: the technology of satellite Orbit Determination by Two-way Tracking (ODTT)

Based on the principle of TWSTFT, the technology of satellite Orbit Determination by Two-way Tracking (ODTT) is proposed in this contribution. In contrast to the TWSTFT, the signal is transmitted from and received by the same station in ODTT. The time delay of the signal from the station to the Geostationary (GEO) satellite, and then back to the station can be precisely measured, which realizes the range determination between the station and the satellite. Based on the determined ranges of several stations and dynamic models for orbit determination, precise satellite orbits can be obtained. In this study, in addition to the ODTT measurement model, the methods of correcting the station hardware delays, the tropospheric and the ionospheric delays are explained in details. In collaboration with several other institutions, National Time Service Center (NTSC), Chinese Academy of Sciences(CAS) setup a Two-way Tracking network of 5 stations in China, and performed a large amount of experiments for GEO satellite orbit determination. The results show that the precision of the range measurements is about 2 cm, and the GEO satellite orbit precision is a few meters with long arc observation. According to the experimental results, the main characters of ODTT are shown as follows: 1) the ranges measured by the ODTT do not include the time difference between the ground and the satellite clocks, which is beneficial for realizing the precise orbit determination; 2) the measurement precision is very high, i.e., about 2 cm; 3) the ODTT utilizes the microwave frequency and the technology of spread spectrum, which supports the orbit determination for satellites of high orbits and the measurements in diverse atmosphere conditions. The ODTT is a new space technology under development. It will support the research of spatial sciences and geosciences in the future.