ground infrastructure operations. However, the use of GPS signals for SSV users, particularly for HEO/GEO missions, has special design challenges. In these missions, the GNSS receiver is at an altitude above the altitude of the GPS constellations. Consequently, the onboard GNSS receivers could only capture the side-lobe signals or main-beam signals originated from satellites on the opposite side of the Earth [10; 11; 12]. The power of side-lobe signals are generally about 20 dB lower than that of the main-beam ones, which would lead to the poorer observation quality [10]. The main-beam signals are 10 to 100 times weaker with limited satellite spatial diversity [13]. Moreover, the GPS satellites at high altitude, depending on the receiver sensitivity, can drastically reduce the navigation solution accuracy of SSV users, due to the very limited number of visible satellites and very poor tracking geometry for the region in the field of view [14; 15; 16]. In spite of these difficulties, specialized GNSS receivers have been designed with increased signal acquisition and weak signal tracking capabilities because of receiver technology improvements and navigation signal modernization [17], such as the Navigator GPS receiver developed at the NASA Goddard Space Flight Center [18], the TOPSTAR 3000 receiver of the European Space Agency (ESA) [19], and the low-cost GNSS system funded by the Italian Space Agency [20]. The concept of GPS tracking in SSV has actually been demonstrated by some flight experiments. For example, the EQUATOR-S spacecraft tracked a GPS satellite from an altitude of about 61,000 km and demonstrated the possibility of a reception of GPS side-lobe signals within a very high eccentricity orbit [21]. A GPS receiver flying on the AMSAT-OSCAR 40 (AO-40) spacecraft at a high inclination, 1000 km by 58,800 km altitude orbit, was developed to support the use of GPS for HEO experiments [22; 23]. The reference orbit generated from the Two-Line Ephemeris (TLE) and the Simplified Deep-space Perturbation Version 4 (SDP4) propagator showed to be in error by about 100 km [24]. In addition, the possibility and feasibility to exploit GNSS navigation in lunar trajectories were also investigated and analyzed [25; 26]. Chang'E 5T was launched by China National Space Administration on 24 October 2014. The mission of Chang'E 5T is lunar flyby and Earth re-entry to conduct crucial tests on capsule design planned to be used in the Chang'E-5 mission. The Chang'E-5T lunar probe is equipped with a high sensitivity GNSS receiver which could capture the GPS and GLOASS code and carrier wave signal. [PERSON] et al. [27] firstly proved the idea of using rocket GPS measurements to determine the injected transfer orbit of Chang'E-5T. [PERSON] et al. [28] conducted Chang'E-5T OD using onboard GPS pseudo-range measurements by dynamic method, and results showed that the position error in the one-h prediction from the OD of 1.5 h arc is less than 109 m. However, the higher accuracy carrier phase measurements were not used in [PERSON] et al. [27] or [PERSON] et al. [28]. For the combined use of pseudo-range and carrier phase measurements in SSV, weighting approach needs to be investigated because of the lack of a priori measurement precision information compared to TSV users. In addition, the specially designed receiver was used in SSV. As an important indicator of GNSS receiver design, the C/N0 given by a receiver would affect the number of visible satellite and the quality of GNSS measurements [29], which is crucial for the OD precision. Consequently, the GPS tracking data quality analysis and GPS-based orbit determination results for Chang'E-5T, as well as their relationship with the C/N0 are discussed in this contribution. The paper is organized as follows: In Section 2, we analyze Chang'E-5T onboard GPS data sensitivity and availability. The number of visual GPS satellites, position dilution of precision (PDOP) values and C1 code errors as a function of time and C/N0 value during the tracking arc are discussed.