_version_ 1866909511893123072
author Issaoun, Sara
Pesce, Dominic W.
Rioja, María J.
Dodson, Richard
Blackburn, Lindy
Keating, Garrett K.
Doeleman, Sheperd S.
Sohn, Bong Won
Jiang, Wu
Hoak, Dan
Yu, Wei
Torne, Pablo
Rao, Ramprasad
Tilanus, Remo P. J.
Martí-Vidal, Iván
Jung, Taehyun
Fitzpatrick, Garret
Sánchez-Portal, Miguel
Sánchez, Salvador
Weintroub, Jonathan
Gurwell, Mark
Kramer, Carsten
Durán, Carlos
John, David
Santaren, Juan L.
Kubo, Derek
Han, Chih-Chiang
Rottmann, Helge
SooHoo, Jason
Fish, Vincent L.
Zhao, Guang-Yao
Algaba, Juan Carlos
Lu, Ru-Sen
Cho, Ilje
Matsushita, Satoki
Schuster, Karl-Friedrich
author_facet Issaoun, Sara
Pesce, Dominic W.
Rioja, María J.
Dodson, Richard
Blackburn, Lindy
Keating, Garrett K.
Doeleman, Sheperd S.
Sohn, Bong Won
Jiang, Wu
Hoak, Dan
Yu, Wei
Torne, Pablo
Rao, Ramprasad
Tilanus, Remo P. J.
Martí-Vidal, Iván
Jung, Taehyun
Fitzpatrick, Garret
Sánchez-Portal, Miguel
Sánchez, Salvador
Weintroub, Jonathan
Gurwell, Mark
Kramer, Carsten
Durán, Carlos
John, David
Santaren, Juan L.
Kubo, Derek
Han, Chih-Chiang
Rottmann, Helge
SooHoo, Jason
Fish, Vincent L.
Zhao, Guang-Yao
Algaba, Juan Carlos
Lu, Ru-Sen
Cho, Ilje
Matsushita, Satoki
Schuster, Karl-Friedrich
contents Frequency Phase Transfer (FPT) is a technique designed to increase coherence and sensitivity in radio interferometry by making use of the non-dispersive nature of the troposphere to calibrate high-frequency data using solutions derived at a lower frequency. While the Korean VLBI Network has pioneered the use of simultaneous multi-band 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 January 2024 on an Earth-sized baseline between the IRAM 30-m in Spain and the JCMT and SMA in Hawai`i. We performed simultaneous observations at 86 and 215 GHz on the bright sources J0958+6533 and OJ287, 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 $\sim$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 co-located 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., ALMA sub-arraying and ngVLA calibration strategies).
format Preprint
id arxiv_https___arxiv_org_abs_2502_18776
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle First frequency phase transfer from the 3 mm to the 1 mm band on an Earth-sized baseline
Issaoun, Sara
Pesce, Dominic W.
Rioja, María J.
Dodson, Richard
Blackburn, Lindy
Keating, Garrett K.
Doeleman, Sheperd S.
Sohn, Bong Won
Jiang, Wu
Hoak, Dan
Yu, Wei
Torne, Pablo
Rao, Ramprasad
Tilanus, Remo P. J.
Martí-Vidal, Iván
Jung, Taehyun
Fitzpatrick, Garret
Sánchez-Portal, Miguel
Sánchez, Salvador
Weintroub, Jonathan
Gurwell, Mark
Kramer, Carsten
Durán, Carlos
John, David
Santaren, Juan L.
Kubo, Derek
Han, Chih-Chiang
Rottmann, Helge
SooHoo, Jason
Fish, Vincent L.
Zhao, Guang-Yao
Algaba, Juan Carlos
Lu, Ru-Sen
Cho, Ilje
Matsushita, Satoki
Schuster, Karl-Friedrich
Instrumentation and Methods for Astrophysics
Frequency Phase Transfer (FPT) is a technique designed to increase coherence and sensitivity in radio interferometry by making use of the non-dispersive nature of the troposphere to calibrate high-frequency data using solutions derived at a lower frequency. While the Korean VLBI Network has pioneered the use of simultaneous multi-band 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 January 2024 on an Earth-sized baseline between the IRAM 30-m in Spain and the JCMT and SMA in Hawai`i. We performed simultaneous observations at 86 and 215 GHz on the bright sources J0958+6533 and OJ287, 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 $\sim$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 co-located 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., ALMA sub-arraying and ngVLA calibration strategies).
title First frequency phase transfer from the 3 mm to the 1 mm band on an Earth-sized baseline
topic Instrumentation and Methods for Astrophysics
url https://arxiv.org/abs/2502.18776