Optical Clock Comparison using VLBI

Scope

Atomic clocks based on optical transitions, optical clocks, have shown much better performances in accuracy and stability than the microwave clocks that have realized the definition of the second since 1967. Therefore we expect the second to be redefined using optical clocks. One of the requirements for a redefinition is that optical clocks can be compared with the accuracy of a few parts in 10^18. Optical fiber links can fulfill this requirement on the thousands-kilometers scale, but cannot be utilized on the intercontinental distance. There are several techniques being pursued such as carrier-phase Two-Way Satellite Time and Frequency Transfer (TWCP), GPS Integer Precise Point Positioning (GPS-IPPP), MicroWave Link (MWL) and European Laser Timing (ELT) in Atomic Clock Ensemble in Space (ACES). Recently, broadband VLBI (Very Long Baseline Interferometry) enabled optical clocks in Italy and Japan to be compared at the low 10^-16 level. In this workshop, we will discuss the use of VLBI for clock comparisons on intercontinental baselines and the research perspectives that are allowed by a more tight relation between frequency metrology and VLBI geodesy and astrometry.

Dedicated technical sessions will then focus on the design of a VLBI optical clock comparison between Italy and Korea using standard VLBI telescopes equipped with triple-band receivers (K, Q, W bands), along with other methods such as optical fibers, GPS-IPPP, ELT, and TWCP.

Organizing Committee Members

• Buseung Cho (KISTI)

• Cecilia Clivati (INRIM)

• Davide Calonico (INRIM)

• Marco Pizzocaro (INRIM)

• Monia Negusini (IRA/INAF)

• Myoung-Sun Heo (KRISS)

• Jungwon Kim (KAIST)

• Taehyun Jung (KASI)

Registration and Meeting links

The workshop will be held online. All the participants are required to register in the registration form below by May 27th, 2021.

Registration form link : https://forms.gle/AvxPnAveNXmS9rNE7

The online meeting links will be sent out to registered participants before the workshop from May 28th, 2021.

If you do not receive the links, please contact c.clivati@inrim.it or hms1005@kriss.re.kr.

Invited talks

• Helen Margolis (NPL): Optical clocks for future time scales and a redefinition of the second

• Gérard Petit (BIPM): Clock comparisons with GNSS IPPP

• Mamoru Sekido(NICT): Transportable Broadband VLBI System for intercontinental frequency link

• Taehyun Jung (KASI): High precision VLBI astrometry & geodesy: multi-band techniques and new perspectives

• Marcello Giroletti (IRA/INAF): INAF and Eating VLBI: status and perspectives

• Ulrich Schreiber (TUM): What can accurate optical Time Transfer do for Space Geodesy?

• Xiaogang Zhang (NIST): Advancing atomic timekeeping with the ytterbium optical lattice clock at NIST and an optical clock network in Boulder

• Shuangjing Xu (KASI): EAVN K-band Geodesy

• Doheung Je (KASI): The Introduction of KVN Phase Calibration System and Local Oscillators

Topics to be discussed in the technical sessions

• Design of a VLBI clock comparison between Italy and Korea.

• Status of INRIM and KRISS optical clocks and fiber links

• Clock comparison using GNSS

• Clock comparison using VLBI

  • K- / triple-band observation and related topics

  • Correlation and related topics

• Near-term and long-term plans of Korea-Italy collaboration

• Scientific goals of the clock comparison

Programs

(June 1st)

07:00 UTC Opening address (Davide Calonico, INRIM)

07:10 UTC [Invited] Optical clocks for future time scales and a redefinition of the second (Helen Margolis, NPL)

07:40 UTC [Invited] Clock comparisons with GNSS IPPP (Gérard Petit, BIPM)

08:10 UTC Break

08:30 UTC [Invited] Transportable Broadband VLBI System for intercontinental frequency link (Mamoru Sekido, NICT)

09:00 UTC [Invited] High precision VLBI astrometry & geodesy: multi-band techniques and new perspectives (Taehyun Jung, KASI)

09:30 UTC [Invited] INAF and Eating VLBI: status and perspectives (Marcello Giroletti , IRA/INAF)

10:00 UTC Break

11:00 UTC Technical Sessions 1

• Optical clocks, Fiber frequency transfer

• K-/Triple-band VLBI clock comparison

13:00 UTC Closing

(June 3rd)

07:00 UTC [Invited] Advancing atomic timekeeping with the ytterbium optical lattice clock at NIST and an optical clock network in Boulder (Xiaogong Zhang, NIST)

07:30 UTC [Invited] What can accurate optical Time Transfer do for Space Geodesy? (Ulrich Shreiber, TUM)

08:00 UTC Break

08:20 UTC [Invited] EAVN K-band Geodesy (Shuangjing Xu, KASI)

08:50 UTC [Invited] The Introduction of KVN Phase Calibration System and Local Oscillators (Doheung Je ,KASI)

09:20 UTC Break

11:00 UTC Technical Sessions 2

• K-/Triple-band VLBI clock comparison

• Scientific goals of the clock comparison

13:00 UTC Closing

Acknowledgments

This work in Italy has been funded by the European Metrology Program for Innovation and Research (EMPIR) projects 18SIB05 ROCIT and 18SIB06 TIFOON. These projects have received funding from the EMPIR programme co-financed by the Participating States and from the European Union’s Horizon 2020 research and innovation programme. This work in Korea was supported by the National Research Council of Science & Technology(NST) grant by the Korea government (MSIP) (No. CPS-20-03-KRISS).