Monitoring of UTC(k)'s using PPP and IGS real-time products

The time transfer technique based on Precise Point Positioning (PPP) has proved to be a very effective technique allowing the comparison of atomic clocks with a precision of a hundred picoseconds, and with latency of 2 days. Using satellite orbit and clock information from the IGS real-time products, it is now possible to compute very precise time transfer solutions based on PPP in near real-time, i.e., with a latency down to some minutes. We present PPP-based time transfer results obtained in near real time with the new version of the GNSS data processing software Atomium, and the satellite products mentioned above. We additionally analyze the results that can be obtained with low latency using the NRCan Ultra-Rapid products (EMU) available with a delay of 90-150 min. From the statistics of the results, it is concluded that the real-time IGS products allow detection of a clock jump larger than 1.5 ns after some minutes; the detection threshold falls down to 0.8 ns when using the EMU products about 2 h later. It is also shown that in near real time, a frequency change larger than 2e-14 can be detected when looking at the last 24 h data or larger than 2e-13 when looking at the last 2 h. As demonstrated, the quality of the monitoring depends on the distance between the two stations, so that distances shorter than about 3,000 km should be preferably used for a near real-time comparison of atomic clocks based on PPP.