A High-frequency Geodetic VLBI Experiment for Optical Clock Comparison
Year: 2026
Type: article
Abstract: An intercontinental metrological clock comparison between Italy and the Republic of Korea was performed by means of geodetic K -band VLBI observations. The comparison involved the hydrogen masers (H-masers) used at Medicina and Sejong radio telescopes. The same clocks were simultaneously compared by a satellite link and by high-precision optical clocks maintained at the National Metrology Institutes, KRISS in Korea and INRIM in Italy, and delivered to VLBI antennas via optical fiber. The H-masers frequency difference was estimated by extrapolating the clock rate from VLBI data using two geodetic VLBI software. This was subsequently compared with clock differences derived by satellite link and by local optical clocks. Results obtained with different approaches were in agreement at the level of 10 −15 s s −1 . This pilot study demonstrates that standard high-frequency ( K -band) geodetic VLBI campaigns could be a viable approach to conduct intercontinental clock comparisons, now only possible via satellite links. This uncertainty can be reduced thanks to the planned installation of new-generation, broadband, high-frequency receivers on the involved telescopes. K / Q / W -band geodetic observations will allow an improvement of the accuracy of the resulting group delays through broad bandwidth synthesis from 20 to 100 GHz. Furthermore, the Frequency Phase Transfer method will also be explored together with the use of PCAL systems installed at the radio telescopes to improve phase stability and thus allow a better estimation of the station clock parameters.
Authors: Monia Negusini, Myoung-Sun Heo, Cecilia Clivati, Shuangjing Xu, Roberto Ricci, Taehyun Jung, Buseung Cho, Matteo Stagni, Claudio Bortolotti, Giuseppe Maccaferri, Federico Perini, Mauro Roma, Do-Young Byun, Do-Heung Je, Marco Pizzocaro, Davide Calonico, Elena Cantoni, Giancarlo Cerretto, Stefano Condio, Giovanni A. Costanzo, Simone Donadello, Irene Goti, Michele Gozzelino, Alberto Mura, Filippo Levi, Matias Risaro, Huidong Kim, Won-Kyu Lee, Chang Yong Park, Dai-Hyuk Yu, Young Kyu Lee, Joon Hyo Rhee, Chanjin Park, Minseong Lee, Hyo Ryoung Kim, Sung-Moon Yoo, Jungho Cho, Jongsoo Kim, Sang-Oh Yi, Ha Su Yoon, Pablo de Vicente, Javier González, Cristina García Miró
Institutions: Istituto di Radioastronomia di Bologna, National Institute for Astrophysics, Korea Research Institute of Standards and Science, Istituto Nazionale di Ricerca Metrologica, Korea Astronomy and Space Science Institute, University of Rome Tor Vergata, Korea Institute of Science & Technology Information, Korea University of Science and Technology, Politecnico di Torino, National Geographic Information Institute, Yebes Observatory, Instituto Geográfico Nacional
Language: English
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $3,325
OpenAlex ID: W7128542299