Time transfer using low cost High-Gain antennas

The objective is to develop and validate an alternative time transfer technique to be used by the scientific community for time transfer between timing laboratories, using high gain antennas. This novel technique can also provide a potential benefit for the Galileo infrastructure in terms of performance and independence, as well as for ESA laboratories towards a combined international realization of UTC(ESA) (time transfer between ESA/ESTEC and ESA/ESOC).

Universal Coordinated Time (UTC) generation relies nowadays mostly on two techniques for time and frequency transfer: Two-Way Satellite Time and Frequency Transfer (TWSTFT) and Global Navigation Satellite Systems (GNSS). Both techniques present the following main characteristics: TWSTFT: accuracy 1-2ns, precision 100ps and usage of small high gain antennas to a geostationary channel in Ku-band with discrete measurements in observation windows. ;GNSS : accuracy 3-5ns, precision 20ps and usage of omnidirectional antennas and free L-Band signals with continuous measurements. TWSTFT remains as the principal technique for time transfer due to the better accuracy (1-2 ns) than GNSS, despite the many advantages in other areas (precision, continuity and cost). In term of cost, TWSTFT requires leasing a dedicated link in a geostationary transponder and dedicated specialized hardware, while GNSS relies on free signals and standard geodetic equipment. Despite being the primary link technique in BIPM for the realization of UTC, only few time Laboratories use TWSTFT while all run GNSS equipment. A previous ESA activity, finalised in 2018, EGEP-ID103 ?Accurate Calibration of Multisystem/Multi-Frequency GNSS Receiver Chains? has led to the development of a procedure and set-up for the full absolute calibration of GNSS chains with omnidirectional antennas. This procedure is expected to foster the use of Galileo in the timing community. However, EGEP-ID103 concluded that further improvements were limited by the calibration and the gain of the omnidirectional antenna (e.g. effects of multipath). This limitation is in principle removed by using a directional high gain antenna. The objective of this activity is to develop a new methodology combining the benefits of both time transfer techniques (TWSTFT and GNSS) by using low cost high gain antennas together with GNSS signals, with the following final performance targets: The expected benefits are in performance, cost and independence. This is deemed feasible relying on free GNSS signals and the better capabilities of high gain antennas in terms of calibration capabilities and gain. Successful experience exists using low cost high gain antennas of up to 3 meter diameter at ESA and within European Industry for supporting Galileo satellites calibration. The existing methodology has to be updated to cover high gain directional antennas calibration, benefits and issues. Then, the effort is devoted to the functional verification and final validation by the deployment of the calibrated high gain antenna chain at ESA/ESTEC and ESA/ESOC to link both time scale realizations towards a combined international realization of UTC(ESA) time scale. Deliverables include the procedure, algorithmic model, software, hardware, a validation campaign between at least two UTC(k) realizations and the final deployment at ESA/ESTEC and ESA/ESOC including an acceptance campaign.