Improved GPS-based time link calibration involving ROA and PTB

Abstract

The calibration of time transfer links is mandatory in the context of international collaboration for the realization of International Atomic Time. In this paper, we present the results of the calibration of the GPS time transfer link between the Real Instituto y Observatorio de la Armada (ROA) and the Physikalisch-Technische Bundesanstalt (PTB) by means of a traveling geodetic-type GPS receiver and an evaluation of the achieved type A and B uncertainty. The time transfer results were achieved by using CA, P3, and also carrier phase PPP comparison techniques. We finally use these results to re-calibrate the two-way satellite time and frequency transfer (TWSTFT) link between ROA and PTB, using one month of data. We show that a TWSTFT link can be calibrated by means of GPS time comparisons with an uncertainty below 2 ns, and that potentially even sub-nanosecond uncertainty can be achieved. This is a novel and cost-effective approach compared with the more common calibration using a traveling TWSTFT station.

Combining GPS, BeiDou, and Galileo Satellite Systems for Time and Frequency Transfer Based on Carrier Phase Observations

“…Considering the existence of hardware delays in the receiver, antenna, and cables when conveying the internal electrical signal, the receiver clock offset usually contains these delays, which can be calibrated in the area of the time and frequency transfer [41,42]. Therefore, this is not included in the present study.…”

Summary of the link calibration between NIM and PTB using a traveling GPS receiver

“…After the suitability for the purpose of the IMEU receiver had been verified [1], the method using it for link calibrations has been developed [2]. The operation mode of IMEU differs from that of the GTR50 receiver which was used in previous successful calibration campaigns [3,4]. There are, however, several similarities.…”

“…The internal reference delays XO1 and XO2 that were measured by SR620 TIC and the difference XOD of XO1 and XO2 that was calculated according to (2) and the corresponding standard deviations of the measurements are listed in TABLE III. So CorD according to (3) and the corresponding standard deviation of the measurements are described as Table 4. It is always considered as an option to use Common-View (CV) instead of All-in View (AV) data analysis to calculate the calibration value for the link as one can expect that most errors cancel in CV.…”

Time link calibration method using a homemade GPS traveling receiver

“…In this link calibration method [2,3] , firstly we do the CCD experiment with TR (including an antenna and an antenna cable) and the GPS receiver R1 that is used for time transfer at timing lab 1 in this link, both receivers are referenced to UTC(k1) and C1 is got.…”

“…In order to contribute to the realization of TAI traveling receivers (TRs) [1] and by a GPS traveling receiver (TR) [2] can be considered. Because portable TWSTFT stations are hardly available and the method by GPS costs much less, we are motivated to implement the link calibration using GPS preferably that is demonstrated in the link calibration between ROA and PTB [2] and in the link calibration between PTB and METAS [3] .…”