KREONET

Overcoming the Limits of Spatiotemporal Measurement Precision in Broadband VLBI for Ultra-Precise Intercontinental Optical Clock Comparison

Objective

• The project integrates the highest-precision time measurement capabilities of optical clocks with the ultra-high spatial resolution of next-generation broadband Very Long Baseline Interferometry (VLBI). Its goal is to enable intercontinental optical clock comparisons at the 10⁻¹⁷ level and beyond, contributing to the redefinition of the second in the international system of units. Additionally, by leveraging advanced high-frequency VLBI technology, the project aims to surpass the current spatial resolution limits of conventional VLBI systems.

Period

June 2022 – May 2027

Collaboration

Korea Research Institute of Standards and Science (KRISS), Korea Institute of Science and Technology Information (KISTI), Korea Advanced Institute of Science and Technology (KAIST), Korea Astronomy and Space Science Institute (KASI)

Funding

79 billion KRW, funded by the National Research Council of Science & Technology’s Creative Convergence Research Program

Key Steps

• Phase 1: Develop and establish high-frequency broadband VLBI systems and component technologies for optical clock comparison using a VLBI observation network on the Korean Peninsula. Validate the limits of spatiotemporal measurement accuracy through domestic VLBI experiments, and conduct joint preliminary research with Italy in preparation for future international comparisons of high-precision optical clocks.
• Phase 2: Conduct intercontinental optical clock comparison research with 10⁻¹⁷ or greater time precision through simultaneous VLBI observations linked to optical frequency clocks.

  - Develop optical clocks with 10⁻¹⁸ accuracy and ensure stable long-term operation. Transmit precise signals to telescopes with minimal noise.

  - Build a high-frequency broadband VLBI observation system based on microwave (MW) signals generated from transmitted frequencies.

  - Perform international optical clock comparisons with Italy’s VLBI, equipped with 22/43/86 GHz receivers, to achieve 10⁻¹⁷ level time comparison precision and 1 mm spatial measurement accuracy.

Expected Benefits

• This project exemplifies a successful convergence of core research infrastructures and expertise in Korea—including VLBI, optical fiber networks/high-performance research networks, low-noise microwave generation, and optical clocks.
• By leveraging the world’s first high-frequency broadband VLBI network, state-of-the-art optical clocks, and globally recognized high-performance optical networks, the project will achieve an unprecedented level of spatiotemporal measurement precision.
• The “second” (time unit), redefined after more than half a century since its initial definition in 1967 due to advancements in science and technology, will face its next redefinition. Through this project, Korea will play a leading role in the redefinition of the second and establish itself as a time-keeping hub in Asia.
• It also contributes to the enhancement of the celestial and terrestrial reference frames that serve as benchmarks for absolute positioning.
• The outcomes are expected to benefit real-world and national initiatives such as real-time crustal deformation monitoring on the Korean Peninsula, climate change analysis, and tracking of Korean space missions. Moreover, it supports the Fourth Industrial Revolution through ultra-precise time and frequency synchronization.
• By securing a sustainable infrastructure for precise spatiotemporal measurement, the project lays the groundwork for new scientific discoveries and provides a foundation for delivering ultra-precise time and space services to a wide range of users.

[Project Concept Diagram]

[Configuration of Domestic and International High-Performance VLBI Data Transmission Networks]