This picture was the 10000th to appear in ESO's photo archive. It was posted to the Your ESO Pictures Flickr group by Adhemar Duro on 30 September 2015. This resource is growing each day with new, wonderful and quirky views of ESO from both the inside and outside. Adhemar's picture is a spectacular night view of Otto, one of the ALMA transporters, with the Milky Way and ALMA antennas as a dramatic backdrop.

People Working for ALMA (1) Spectacular Scene Like an SF Movie: Interview with Professional Operators of Giant Transporters

ALMA is an international project in cooperation with 22 countries and regions where several hundreds of people from various fields are working together as a team with astronomers who carry out research with ALMA.
This series of interviews features such people who work for the ALMA project. This first article introduces a team in charge of carrying giant antennas, a key instrument of a radio telescope, with a special vehicle called “transporter”. We interviewed with two backseat players who work behind the scenes: associate professor Norikazu Mizuno who leads the ALMA engineering group, and a local operator Juan Salamanca.

ALMA 66 Antennas Configuration Changeable at 5000 m

— ALMA is a radio telescope to observe the universe with 66 movable parabolic antennas that can be arranged to a required configuration most suitable for the reception of radio waves from a target object. How often do you move the antennas?

Mizuno: Currently, moving 10 to 20 antennas every month. Antennas are moved one by one from a compact configuration to a larger one, and then placed back to a smaller one. This process is repeated many times.

 

ALMA array from the air

ALMA antennas extended at the Array Operations Site (AOS)

— What is the difference between the extended and compact configurations?

Mizuno: With an extended space between antennas, we can achieve higher resolution that allows us to observe details of distant objects like a zoom lens of a camera. On the other hand, with a narrowed space between antennas, we can see the extended object entirely like using a wide zoom lens. Antenna configuration can be variously arranged according to the target objects and research purposes. This is a great advantage of ALMA.

 

— So, antennas are arranged differently depending on each astronomer’s target of observations.

Mizuno: Actually ALMA makes announcement of the antenna configuration scheduled from October to next September every year. Astronomers around the world see the schedule and submit proposals for a period to meet the needs for their observations.

 

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Planetary forming disk around HL Tau around 450 light years away, which was observed with an extended antenna configuration. ©ALMA (ESO / NAOJ / NRAO)

ALMA observes a giant sunspot (1.25 millimetres)

A sunspot observed with a compact antenna configuration ©ALMA (ESO / NAOJ / NRAO)

— Do you move all of 66 antennas every time?

Mizuno: Among 66 antennas, 16 Japanese antennas (four 12 m and twelve 7-m antennas) composing the Atacama Compact Array (ACA) are not necessary to be moved a lot, because they keep a very compact configuration to observe the universe with a wide field of view. A required condition for observation at this moment is that 45 antennas out of the remaining fifty 12-m antennas are set to a certain position.

When changing the configuration, we don’t move 45 antennas all together. Instead, we start with 15 antennas and gradually make a larger configuration over a week or so, and then make 3-week observations with this arrangement. And then, move another group of 15 antennas over a week to make a configuration larger than the previous one. In this way, we extend the antenna configuration bit by bit and do the same when we make a smaller configuration.

 

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Compact configuration of 16 ACA antennas. ©ALMA (ESO / NAOJ / NRAO)

 

Why 100-ton Giant Antennas are Carried One by One?

— I was surprised that a 100-ton giant antenna is carried by the transporter, a vehicle with tires. How did you come up this idea?

Mizuno: In a conventional method, railroad tracks and wagons were used for antenna transportation in radio interferometers with multiple antennas like ALMA, such as the Nobeyama Millimeter Array (NMA *Ended its scientific operations), and the Karl G. Jansky Very Large Array (VLA *One of the large radio telescopes operated by the U.S. National Radio Astronomy Observatory) in New Mexico.

However, unlike these telescopes, ALMA has about 200 antenna setting points. Moreover, the land is not flat enough. There are mountains and valleys along the way when we move the antennas to the most distant part. It’s not realistic at all to set railroad tracks on such a rough surface.

 

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Norikazu Mizuno (Associate professor at the NAOJ Chile Observatory)

— From the aerial photo of the Atacama Desert, the areas around the Array Operations Site (AOS) look rather flat but actually there are height differences.

Mizuno: Right. And, it could be a threat to life to work with the antenna at the 5000-m high site for a long time. Then, for the maintenance of the antenna, we have to transport it down to the Operations Support Facility (OSF) at 2900m.

For such a long transportation, it could be very costly if we did it with railroads. Therefore, we decided to use a transporter with tires for antenna transportation.

 

Mizuno Norikazu (Associate Professor at the NAOJ Chile Observatory)

Mizuno Norikazu (Associate Professor at the NAOJ Chile Observatory)

From 1997, engaged in on-site operations and starting up of the observatory of NANTEN and NANTEN2 (developed by Nagoya University) at Las Campanas Observatory, Chile and conducted observational research focused on the Magellanic Clouds. From 2008, assigned to the ALMA project and involved in the construction, antenna performance evaluation, and system verification, etc. Currently, as a manager of the Array Maintenance Group at the Joint ALMA Observatory (JAO), leading a team that covers operations and maintenance of antennas and other equipment, as well as future development for additional capabilities of ALMA.
Juan Carlos Salamanca (Transporter Operator at the Joint ALMA Observatory)

Juan Carlos Salamanca (Transporter Operator at the Joint ALMA Observatory)

Entered the Navy very young where he worked for 21 years and graduated as Electronic Technician in Radars, Electronic Technician in Avionics, and Engineer in Control and Instrumentation. Since 2008, working at the Joint ALMA Observatory as Antenna Transporter Operator.

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