First Frequency Phase Transfer from the 3 mm to the 1 mm Band on an Earth-sized Baseline

Abstract Frequency phase transfer (FPT) is a technique designed to increase coherence and sensitivity in radio interferometry by making use of the nondispersive nature of the troposphere to calibrate high-frequency data using solutions derived at a lower frequency. While the Korean very long baseline interferometry (VLBI) network has pioneered the use of simultaneous multiband systems for routine FPT up to an observing frequency of 130 GHz, this technique remains largely untested in the (sub)millimeter regime. A recent effort has been made to outfit dual-band systems at (sub)millimeter observatories participating in the Event Horizon Telescope (EHT) and to test the feasibility and performance of FPT up to the observing frequencies of the EHT. We present the results of simultaneous dual-frequency observations conducted in 2024 January on an Earth-sized baseline between the IRAM 30-m in Spain and the James Clerk Maxwell Telescope (JCMT) and Submillimeter Array (SMA) in Hawai‘i. We performed simultaneous observations at 86 and 215 GHz on the bright sources J0958+6533 and OJ 287, with strong detections obtained at both frequencies. We observe a strong correlation between the interferometric phases at the two frequencies, matching the trend expected for atmospheric fluctuations and demonstrating for the first time the viability of FPT for VLBI at a wavelength of ∼1 millimeter. We show that the application of FPT systematically increases the 215 GHz coherence on all averaging timescales. In addition, the use of the colocated JCMT and SMA as a single dual-frequency station demonstrates the feasibility of paired-antenna FPT for VLBI for the first time, with implications for future array capabilities (e.g., Atacama Large Millimeter/submillimeter Array subarraying and ngVLA calibration strategies).

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Publication Details

Journal
The Astronomical Journal
Published
2025-03-26
DOI
https://doi.org/10.3847/1538-3881/adbb55
Citations
4
Primary Topic
Radio Astronomy Observations and Technology
Type
article
Field-Weighted Citation Impact
4.62

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article

First Frequency Phase Transfer from the 3 mm to the 1 mm Band on an Earth-sized Baseline

Ru-Sen Lu, Juan L. Santaren, Dominic W. Pesce, Ilje Cho et al.
4 citations
The Astronomical Journal
Radio Astronomy Observations and Technology
4.62
article

First Frequency Phase Transfer from the 3 mm to the 1 mm Band on an Earth-sized Baseline

Ru-Sen Lu, Juan L. Santaren, Dominic W. Pesce, Ilje Cho, Jonathan Weintroub, Sheperd S. Doeleman, Garrett K. Keating, Satoki Matsushita, María José Rioja, Jason Soohoo, Salvador Sánchez, R. P. J. Tilanus, Bong Won Sohn, Guang-Yao Zhao, Taehyun Jung, Juan Carlos Algaba, Vincent L. Fish, Derek Kubo, Ramprasad Rao, K. Schüster, M. Sánchez‐Portal, Helge Rottmann, Chih-Chiang Han, Pablo Torné, Richard Dodson, C. Krämer, C. Durán, I. Martí‐Vidal, Mark Gurwell, Sara Issaoun, John David, Lindy Blackburn, Garret Fitzpatrick, Wei Yu, Dan Hoak, Wu Jiang
article en
4 citations

Abstract

Abstract Frequency phase transfer (FPT) is a technique designed to increase coherence and sensitivity in radio interferometry by making use of the nondispersive nature of the troposphere to calibrate high-frequency data using solutions derived at a lower frequency. While the Korean very long baseline interferometry (VLBI) network has pioneered the use of simultaneous multiband systems for routine FPT up to an observing frequency of 130 GHz, this technique remains largely untested in the (sub)millimeter regime. A recent effort has been made to outfit dual-band systems at (sub)millimeter observatories participating in the Event Horizon Telescope (EHT) and to test the feasibility and performance of FPT up to the observing frequencies of the EHT. We present the results of simultaneous dual-frequency observations conducted in 2024 January on an Earth-sized baseline between the IRAM 30-m in Spain and the James Clerk Maxwell Telescope (JCMT) and Submillimeter Array (SMA) in Hawai‘i. We performed simultaneous observations at 86 and 215 GHz on the bright sources J0958+6533 and OJ 287, with strong detections obtained at both frequencies. We observe a strong correlation between the interferometric phases at the two frequencies, matching the trend expected for atmospheric fluctuations and demonstrating for the first time the viability of FPT for VLBI at a wavelength of ∼1 millimeter. We show that the application of FPT systematically increases the 215 GHz coherence on all averaging timescales. In addition, the use of the colocated JCMT and SMA as a single dual-frequency station demonstrates the feasibility of paired-antenna FPT for VLBI for the first time, with implications for future array capabilities (e.g., Atacama Large Millimeter/submillimeter Array subarraying and ngVLA calibration strategies).

The Astronomical JournalVol. 169(4)
Institute of Astronomy and Astrophysics, Academia Sinica (TW), Woodwell Climate Research Center (US), Harvard University (US), University of Arizona (US), Universitat de València (ES), Yonsei University (KR), Korea Astronomy and Space Science Institute (KR), Parc Científic de la Universitat de València (ES), University of Malaya (MY), Institut de Radioastronomie Millimétrique (FR), Center for Astrophysics Harvard & Smithsonian (US), Instituto de Radioastronomía Milimétrica (ES), Spanish National Observatory (ES), Max Planck Institute for Radio Astronomy (DE), International Centre for Radio Astronomy Research (AU), Massachusetts Institute of Technology (US)
National Science Foundation, Smithsonian Institution, National Aeronautics and Space Administration, John Templeton Foundation, Gordon and Betty Moore Foundation, Harvard University, Space Telescope Science Institute, National Astronomical Research Institute of Thailand, European Commission, Academia Sinica, Generalitat Valenciana, Korea Astronomy and Space Science Institute, Max-Planck-Gesellschaft, Centre National de la Recherche Scientifique, National Astronomical Observatory of Japan, Smithsonian Astrophysical Observatory, Science and Technology Facilities Council, National Science Fund for Distinguished Young Scholars
Openalex Percentile: Top 6%
Radio Astronomy Observations and Technology
4.62
DOIOpen Access PDFOpenAlex
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