NAOJ Director General Saku Tsuneta shows us the unseen side of ALMA, the world’s largest radio telescope array
The Atacama Large Millimeter/submillimeter Array (ALMA) is the world’s largest radio telescope array, located in Atacama (approximately 5,000 m altitude), Chile. ALMA development and operations are carried out by a global partnership between East Asia (led by the National Astronomical Observatory of Japan, NAOJ), Europe (led by the European Southern Observatory, ESO), and North America (led by the United States National Radio Astronomy Observatory, NRAO) in cooperation with the Republic of Chile.
ALMA observes radio waves, which are invisible to the human eye. The “Invisible Universe” revealed by ALMA has captured the interest of astronomers, scientists in other fields and the general public. ALMA is at the forefront of science, helping to answer questions about the ultimate origins of the Earth and humanity, with the ability to image the footprints of planets forming around distant stars; track the distribution and evolution of organic material in protoplanetary disks; and detect oxygen released by supernovae in the early Universe. But behind these now-famous results, there is an untold story of technological development and international collaboration.
Results are only half the story
ALMA has just celebrated its 10th anniversary since ALMA Early Science started on 30th September 2011. But the story starts much earlier. The first of ALMA’s 66 antennas, a 12-metre diameter antenna built by Mitsubishi Electric Corporation on behalf of NAOJ, was delivered to the operations site in 2008. Before that, construction of the site started in 2003, based on site testing as far back as 1995, following an earlier discovery that the site would be excellent for future radio astronomy by Japanese astronomers in 1992.
ALMA’s breathtaking astronomy images are only half the story. Japan with other Asian nations and other partners are proud to have made key contributions in technology development, in the unseen half of the story.
East-Asian contributions to ALMA
NAOJ leads ALMA operations and development in East Asia. Other contributors include the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).
The original ALMA plan calls for receivers of 10 different frequency bands. Of these, East Asian partners are responsible for the highest frequency (787-950 GHz, band 10), the most technologically challenging receivers, and the lowest frequency (35-50 GHz, band 1) with two other intermediate frequency bands (125-163 GHz, band 4; 385-500 GHz, band 8). The band 10 receivers were produced in-house at NAOJ. The super-conducting electronics necessary for this frequency range can only be manufactured at a handful of facilities scattered around the world. These systems are already indispensable in modern radio astronomy and will only continue to grow in importance as other fields such as quantum computing mature. The SIS (Superconductor-Insulator-Superconductor) junctions we developed for the band 10 receivers received the Super Conductor Science and Technology Award from the Society of Non-Traditional Technology in 2010. NAOJ completed delivery of the band 10 receivers in 2013, and they are now producing scientific results.
Now, the development and construction of the band 1 receivers are being led by ASIAA with contributions from NAOJ and other partners. In particular, a 3D metal printer at NAOJ is being employed to produce the corrugated horns needed for the band 1 receivers. Driven by our commitments to provide ALMA components, the Advanced Technology Center (ATC) in NAOJ’s Mitaka Headquarters has evolved into an in-house factory for radio astronomy receiver systems, with a focus on super-conducting technologies (refer to photo).
The East-Asian ALMA Regional Center is also located at NAOJ’s Mitaka Headquarters. Regional centers maximise the scientific return from ALMA by providing user support for the astronomy community for the entire process from proposal preparation, to preparing for observations, to delivery of the final calibrated science data. Even when ALMA suspended observations for a year due to the global COVID-19 pandemic, the East-Asian Regional Center stayed active, processing and releasing previously acquired data, and providing a point of contact with the community for their inquiries and requests.
ALMA’s innovative management
In addition to experiments to develop technology, ALMA’s management structure, with three effectively equal major partners, was a grand experiment. No one knew if it could actually work. Even today, when I show ALMA’s organisational chart to project managers in other fields, they can’t believe that it actually works. But ALMA’s results show that it works very well, and very equitably. Japan finances 25% of ALMA and, after operational overheads, open-skies use, and securing Chilean observing time are accounted for, Japan is proportionally allotted about 21.4% of the observing time. Observations using this time produce about 20% of the scientific reports from ALMA.
In many ways, more important than the operational capital is the system of in-kind contributions where partners can develop and contribute technology as part of their responsibility to the project. Within this framework, NAOJ has led the development of key elements.
The ALMA Development Program
The technology and management behind ALMA have enabled scientific results of the absolutely highest societal impact. For instance, ALMA had the highest sensitivity of all the facilities used in the Event Horizon Telescope observations that produced the first-ever image of a black hole shadow that appeared on newspaper front pages, primetime news programs and pop-culture webpages around the world. Without ALMA, the clarity, visual impact, and social response would have been greatly reduced.
ALMA will continue producing scientific results of the highest calibre throughout the 2020s. But as the decade of development work to produce the first ALMA image shows, it is already time to start upgrade work to remain competitive in the 2030s. “The ALMA Development Program: Roadmap to 2030” calls for doubling ALMA’s angular resolution, sensitivity and bandwidth. In Japan, the ALMA upgrade plan has been selected as part of the ROADMAP2020 for large science-infrastructures by the Ministry of Education, Culture, Sports, Science and Technology (MEXT)’s Council for Science and Technology.
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