First Very Long Baseline Interferometry Fringe Detection at 690 GHz
Journal article, 2026
We report the first very long baseline interferometry (VLBI) experiment conducted in the 690 GHz atmospheric window. On 2024 November 21, observations with the Atacama Large Millimeter/submillimeter Array, the Atacama Pathfinder EXperiment (APEX), and the James Clerk Maxwell Telescope (JCMT) were carried out using ALMA's newly developed Band 9 phasing capability. Fringes were detected on the ALMA-APEX baseline during a scan of the quasar J0423-0120, with a signal-to-noise ratio of similar to 12 and useful fringe recovery over solution intervals of order tens of seconds, representing the highest-frequency ground-based VLBI fringe detection reported to date. No fringes were found on the ALMA-JCMT baseline, despite excellent weather conditions, consistent with sensitivity predictions and supporting baseline performance models. The ALMA Phasing System maintained stable phasing at Band 9 for similar to 1-2 minutes before gradually degrading, indicating limitations under these observing conditions. Our analysis shows that, under excellent weather conditions, 690 GHz VLBI can still support fringe recovery over short solution intervals, despite rapid atmospheric phase fluctuations at these frequencies. This work validated key elements of near-terahertz VLBI operation and establishes a technical foundation for routine observations in the 690 GHz atmospheric window.
Author
Ming-Tang Chen
Academia Sinica
Geoffrey B. Crew
Massachusetts Institute of Technology (MIT)
Dan Bintley
East Asian Observatory
Alan Roy
Max Planck Society
Keiichi Asada
Academia Sinica
Johnson Han
Academia Sinica
Kuan-Yu Liu
East Asian Observatory
Chin-Shin Chang
Atacama Large Millimeter-submillimeter Array (ALMA)
University of Geneva
Andrea McCloskey
East Asian Observatory
Yiqing Song
Atacama Large Millimeter-submillimeter Array (ALMA)
Vincent Fish
Massachusetts Institute of Technology (MIT)
Michael Lindqvist
Chalmers, Space, Earth and Environment, Onsala Space Observatory
Satoki Matsushita
Academia Sinica
Lynn D. Matthews
Massachusetts Institute of Technology (MIT)
Hugo Messias
Atacama Large Millimeter-submillimeter Array (ALMA)
Jan F. Wagner
Max Planck Society
Ue-Li Pen
Academia Sinica
Derek Kubo
Academia Sinica
Teddy Huang
Academia Sinica
Philippe Raffin
Academia Sinica
Chih-Wei L. Huang
Academia Sinica
Pierre Martin-Cocher
Academia Sinica
Geoffrey C. Bower
Academia Sinica
East Asian Observatory
Patrick Koch
Academia Sinica
Lisa Kewley
Harvard-Smithsonian Center for Astrophysics
Timothy Norton
Harvard-Smithsonian Center for Astrophysics
Nimesh Patel
Harvard-Smithsonian Center for Astrophysics
Paul T. P. Ho
East Asian Observatory
Per Friberg
East Asian Observatory
Izumi Mizuno
East Asian Observatory
Akil Marshall
East Asian Observatory
Andrey M. Baryshev
University of Groningen
Heino Falcke
Radboud University
Thomas Greve
Technical University of Denmark (DTU)
Jacques Lepine
University of Sao Paulo (USP)
Manuel Fernandez Lopez
National University of La Plata
Silvina Cichowolski
CONICET–UBA
Carlos Valotto
Instituto de Astronomía Teórica y Experimental (IATE)
National University of Córdoba
Ciriaco Goddi
National Institute for Nuclear Physics
Istituto nazionale di astrofisica (INAF)
University of Cagliari
Guillermo Gimenez de Castro
Mackenzie Presbyterian University
CONICET–UBA
Fatima Salete Correra
University of Sao Paulo (USP)
Marianne Vestergaard
University of Copenhagen
Jes Kristian Jorgensen
University of Copenhagen
Martin E. Pessah
Niels Bohr Institute
Roman Gold
Heidelberg University
University of Southern Denmark
Publications of the Astronomical Society of the Pacific
0004-6280 (ISSN) 1538-3873 (eISSN)
Vol. 138 8 084104ERGODIC: Combined passenger and goods transportation in suburb traffic
European Commission (EC) (F-ENUAC-2022-0003), 2023-10-01 -- 2026-09-30.
VINNOVA (ERGODIC), 2023-10-01 -- 2026-09-30.
European Commission (EC) (F-DUT-2022-0078), 2023-10-01 -- 2026-09-30.
Subject Categories (SSIF 2025)
Atom and Molecular Physics and Optics
Fusion, Plasma and Space Physics
Astronomy, Astrophysics, and Cosmology
DOI
10.1088/1538-3873/ae92b6