VLBI receiver chain monitoring

0396960 - ÚFE 2014 RIV CZ eng C - Conference Paper (international conference)
Michálek, V. - Kodet, J. - Schreiber, U. - Ploetz, Ch. - Procházka, I. - Pánek, Petr
VLBI receiver chain monitoring.
Proceeding 2013 Joint European Frequency and Time Forum and International Frequency Control Symposium, EFTF/IFC 2013. Praha: IEEE, 2013, s. 854-856. ISBN 9781479903429.
[2013 Joint UFFC, EFTF and PFM Symposium. Prague (CZ), 21.07.2013-25.07.2013]
Institutional support: RVO:67985882
Keywords : Frequency standards * Calibration * Two-way time transfers
Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering

he most demanding goal of the Global Geodetic Observing System initiative is the definition of station positions to an accuracy of 1mm and the corresponding velocities to 0.1 mm/year. The main remaining sources of error are caused by systematics, leading to intra- and inter- technique biases. In this work, we have focused on Very Long Base Interferometry (VLBI) and phase calibration generator currently in operation. This unit is injecting calibration tones into the detection chain through an input coupler located near the input of the antenna. The tones propagate further through entire detection chain and are recorded with the observed signal. Then they are extracted in post processing. These tones are generated out of an atomic frequency standard. The supplied frequency is significantly influenced by temperature and mechanical changes since usually a long cable is employed to bring the frequency to the calibration unit. To monitor the electrical length of the cable, calibration with a picosecond precision is essential. We have redesigned a phase calibration unit so that it enables the implementation of the Two Way Time Transfer (TWTT) method on single coaxial cable using two event timers to monitor the electrical length of the critical cable. Such a system has been installed in parallel to the unit currently in operation. The comparison of the TWTT method with previous measurement method is presented
Permanent Link: http://hdl.handle.net/11104/0224642