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| ALMA Phasing Project | |
|---|---|
| Name | ALMA Phasing Project |
| Established | 2011 |
| Location | Atacama Desert, Chile |
ALMA Phasing Project
The ALMA Phasing Project enabled the Atacama Large Millimeter/submillimeter Array to operate as a phased array for very long baseline interferometry, connecting ALMA to global networks such as the Event Horizon Telescope and the Global mm-VLBI Array. It integrated instrumentation, firmware, and software to coherently sum signals from ALMA's 12-meter antennas, allowing participation in campaigns that include observatories like the Submillimeter Array, James Clerk Maxwell Telescope, and the Large Millimeter Telescope Alfonso Serrano. The program coordinated international teams from institutions including the National Radio Astronomy Observatory, the Max Planck Institute for Radio Astronomy, and the European Southern Observatory.
The project converted the Atacama Large Millimeter/submillimeter Array into a single large aperture for VLBI by phasing its 66 antennas, interfacing with facilities such as the Very Long Baseline Array, IRAM 30-meter Telescope, NOEMA, and the South Pole Telescope. Key partners included the National Science Foundation, the National Astronomical Observatory of Japan, the National Radio Astronomy Observatory, and the Max Planck Society, with operational contexts at the ALMA Observatory site in the Atacama Desert. Development involved teams from the Harvard-Smithsonian Center for Astrophysics, the Academia Sinica Institute of Astronomy and Astrophysics, and the European Southern Observatory.
Phasing required hardware such as a dedicated phasing processor, hydrogen masers for timing, and fiber-optic distribution systems, developed with contributions from the Max Planck Institute for Radio Astronomy, MIT Haystack Observatory, and industrial partners like Thales Group and Mitsubishi Electric. The design implemented coherent delay tracking, fringe-fitting algorithms, and realtime feedback loops leveraging software stacks from the National Radio Astronomy Observatory, CASA (Common Astronomy Software Applications), and teams at the Jet Propulsion Laboratory. The system used cryogenic receivers consistent with ALMA Bands and integrated with backend recorders comparable to systems at the W. M. Keck Observatory and the Green Bank Telescope.
Science objectives targeted high-angular-resolution imaging of compact sources including supermassive black holes in galaxies like Messier 87 and Sagittarius A*, compact jets in active galactic nuclei observed by the Very Large Array, and maser emission studied at the Max Planck Institute for Radio Astronomy. Observational campaigns coordinated with the Event Horizon Telescope and monitoring programs at the Fermi Gamma-ray Space Telescope, Chandra X-ray Observatory, and Hubble Space Telescope to provide multiwavelength context. The project enabled polarimetry and spectral line VLBI studies relevant to research on NGC 4258, Centaurus A, and star-forming regions in the Orion Nebula with synergy to the Spitzer Space Telescope and ALMA legacy programs.
Commissioning involved test observations with partners such as the Submillimeter Array, IRAM, and the Large Millimeter Telescope Alfonso Serrano, demonstrating phase stability and coherence times validated against standards from the International Astronomical Union and timekeeping via the International Bureau of Weights and Measures. Performance metrics compared sensitivity and baseline coverage with arrays like the Very Long Baseline Array and facilities operated by the National Radio Astronomy Observatory, showing successful integration into global VLBI runs that used correlation centers at the Max Planck Institute for Radio Astronomy and the MIT Haystack Observatory.
Management was multinational, involving governance by organizations including the European Southern Observatory, the National Science Foundation, the National Astronomical Observatory of Japan, and the National Research Council (Canada), with science coordination through working groups connected to the Event Horizon Telescope Collaboration, the Global mm-VLBI Array, and academic partners such as the Harvard-Smithsonian Center for Astrophysics and the University of Arizona. Funding and project oversight engaged agencies like the Ministry of Education, Culture, Sports, Science and Technology (Japan), the Deutsche Forschungsgemeinschaft, and the Natural Sciences and Engineering Research Council of Canada.
The system contributed crucial baselines to the Event Horizon Telescope images of Messier 87's black hole and provided high-sensitivity baselines for polarization studies of Sagittarius A* that informed theoretical work by groups at the Institute for Advanced Study and the Perimeter Institute. Results appeared in collaborations with teams from the Max Planck Institute for Radio Astronomy, the Harvard-Smithsonian Center for Astrophysics, and the Kavli Institute for Theoretical Physics. The project enabled VLBI detections of compact emission in sources such as 3C 273, BL Lacertae, and PKS 1830-211, and facilitated maser astrometry relevant to distance measurements used by groups at the European Southern Observatory and the National Radio Astronomy Observatory.
Planned upgrades include increased bandwidth, enhanced phasing algorithms developed in collaboration with the Jet Propulsion Laboratory and MIT Haystack Observatory, and integration with next-generation facilities such as the Square Kilometre Array pathfinders and the Next Generation Very Large Array. Prospective work involves partnerships with the European Research Council-funded teams, institutions like the Max Planck Society, and coordination with space missions from agencies including NASA and the European Space Agency to expand multiwavelength VLBI capabilities.
Category:Radio astronomy projects