First Very Long Baseline Interferometry Fringe Detection at 690GHz

@misc{chen2026first,
  title = {{First Very Long Baseline Interferometry Fringe Detection at 690GHz}},
  author = {Ming-Tang Chen and Geoffrey B. Crew and Dan Bintley and Alan Roy and Keiichi Asada and Johnson Han and Kuan-Yu Liu and Chin-Shin Chang and Andrea McClöskey and Yiqing Song and Vincent Fish and Michael Lindqvist and Satoki Matsushita and Lynn D. Matthews and Hugo Messias and Jan F. Wagner and Ue-Li Pen and Derek Kubo and Teddy Huang and Philippe Raffin and Chih-Wei L. Huang and Pierre Martin-Cocher and Geoffrey C. Bower and Patrick Koch and Lisa Kewley and Timothy Norton and Nimesh Patel and Paul T. P. Ho and Per Friberg and Izumi Mizuno and Akil Marshall and Andrey M. Baryshev and Heino Falcke and Thomas Greve and Jacques Lepine and Manuel Fernández López and Silvina Cichowolski and Carlos Valotto and Ciriaco Goddi and Guillermo Giménez de Castro and Fátima Salete Correra and Marianne Vestergaard and Jes Kristian Jørgensen and Martin E. Pessah and Roman Gold},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.09886},
  eprint = {2609.09886},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.09886},
  note = {CC BY 4.0},
}

TY  - UNPB
TI  - First Very Long Baseline Interferometry Fringe Detection at 690GHz
AU  - Ming-Tang Chen
AU  - Geoffrey B. Crew
AU  - Dan Bintley
AU  - Alan Roy
AU  - Keiichi Asada
AU  - Johnson Han
AU  - Kuan-Yu Liu
AU  - Chin-Shin Chang
AU  - Andrea McClöskey
AU  - Yiqing Song
AU  - Vincent Fish
AU  - Michael Lindqvist
AU  - Satoki Matsushita
AU  - Lynn D. Matthews
AU  - Hugo Messias
AU  - Jan F. Wagner
AU  - Ue-Li Pen
AU  - Derek Kubo
AU  - Teddy Huang
AU  - Philippe Raffin
AU  - Chih-Wei L. Huang
AU  - Pierre Martin-Cocher
AU  - Geoffrey C. Bower
AU  - Patrick Koch
AU  - Lisa Kewley
AU  - Timothy Norton
AU  - Nimesh Patel
AU  - Paul T. P. Ho
AU  - Per Friberg
AU  - Izumi Mizuno
AU  - Akil Marshall
AU  - Andrey M. Baryshev
AU  - Heino Falcke
AU  - Thomas Greve
AU  - Jacques Lepine
AU  - Manuel Fernández López
AU  - Silvina Cichowolski
AU  - Carlos Valotto
AU  - Ciriaco Goddi
AU  - Guillermo Giménez de Castro
AU  - Fátima Salete Correra
AU  - Marianne Vestergaard
AU  - Jes Kristian Jørgensen
AU  - Martin E. Pessah
AU  - Roman Gold
PY  - 2026
DA  - 2026/09/09
PB  - arXiv
DO  - 10.48550/arxiv.2609.09886
UR  - https://arxiv.org/abs/2609.09886
AB  - 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 ~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 ~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.
ER  -