Objectives The accuracy and integrity of real-time orbits and clocks are essential for achieving high-precision and assured positioning within global navigation satellite system (GNSS). Current assessments mainly focus on the short-term accuracy of real-time products from various analysis centers, and there is a lack of extensive research on the integrity of real-time orbits and clocks.

Methods This paper takes the real-time orbit and clock products of Chinese Academy of Sciences (CAS) in 2022 as a case study and evaluates the performance of products from the perspectives of long-term products accuracy and dynamic precise point positioning (PPP) accuracy. It also assesses the distribution characteristics of signal-in-space user range error of real-time orbit and clock products by analyzing instantaneous signal-in-space user range error (IURE) calculated by 100 uniformly distributed stations worldwide. The integrity support information for CAS real-time orbit and clock products is computed.

Results By comparing CAS real-time orbits and clocks with post-processed precision products provided by Deutsches GeoForschungsZentrum（GFZ）, it is observed that the orbit accuracy of GPS and Galileo is better than 5 cm, with a standard deviation of clock errors better than 0.08 ns. However, the orbit accuracy of BDS and GLONASS is better than 15 cm, with a standard deviation of clock errors better than 0.3 ns. The kinematic PPP using CAS real-time products is conducted with observations collected from 28 globally distributed stations. The positioning accuracy of PPP with the combined four GNSS systems is better than 4 cm, and the corresponding convergence time is better than 11 min. The IURE root mean square (RMS) for GPS and Galileo is better than 4 cm, and the distribution of IURE can be accepted as a Gaussian distribution. GLONASS exhibits an IURE RMS within 10 cm, with noticeable differences among satellites, leading to an obvious leptokurtic and fat-tailed distribution. The BDS demonstrates an IURE RMS better than 11 cm, but the IURE distribution differs among different types of satellites, and BDS-3 satellites from Shanghai Engineering Center for Microsatellites （SECM） display distinct bimodal characteristics. Regarding the prior probability of constellation fault and satellite fault, the prior probability of GPS constellation fault is the smallest, which is 5.2×10^-5, while the prior probability of constellation fault of other systems is less than 1.0×10^-3 except for BDS-2. The prior probability of GLONASS satellite fault reaches 2.7×10^-3, and the prior probability of Galileo satellite fault is the smallest, which is 8.7×10^-4. Regarding envelope standard deviation and standard deviation of signal-in-space user range error, the difference of these two standard deviations of GPS and Galileo is within 4 cm, the difference of these two standard deviations of GLONASS is basically greater than 5 cm, and the difference of envelope standard deviation between BDS-2 and BDS-3 is larger than that of standard deviation.

Conclusions The accuracy of BDS and GLONASS real-time orbit and clock products provided by CAS needs to be further improved to support high-precision and assured positioning.