ALMA Band-5 Receivers

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A crystal-clear sky on any night is always a joy to behold. But if you are on the Chajnantor Plateau, at 5000 metres altitude in the Chilean Andes and one of the best places in the world for astronomical observations, it could be an experience that you’ll remember for your whole life. This panoramic view of Chajnantor shows the antennas of the Atacama Large Millimeter/submillimeter Array (ALMA) against a breathtaking starry night sky. In the foreground, we can see some of ALMA’s antennas, working together. The plateau appears curved, because of the effect of the wide-angle lens used. ALMA is the world’s most powerful telescope for studying the Universe at submillimetre and millimetre wavelengths. Construction work for ALMA will be completed in 2013, and a total of 66 of these high-precision antennas will be operating on the site. At the moment, the telescope is in its initial phase of Early Science Observations. Even though it is not fully constructed, the telescope is already producing outstanding results, outperforming all other submillimetre arrays. In the sky above the antennas, countless stars shine like distant jewels. Two other familiar celestial objects also stand out. First, the image is crowned by the Moon. Second, outshone by the glow of the Moon, it is possible to distinguish the Milky Way as a hazy stripe across the sky. Dark regions within the band are areas where the light from background stars is blocked by interstellar dust. This photograph was taken by ESO Photo Ambassador, Babak Tafreshi. Babak is founder and leader of The World At Night, an international project to produce and exhibit a collection of stunning photographs and time-lapse videos of the world’s landmarks with a backdrop of the most beautiful celestial wonders. ALMA, an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ALMA construction and operations are led on behalf of Europe by ESO, on behalf of North America by the National Radio Astronomy Observatory (NRAO), and on behalf of East Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA. Links More about ALMA at ESO Joint ALMA Observatory ESO Photo Ambassadors

The Atacama Large (sub)Millimeter Array, ALMA, is located at an altitude of over 5000 meters on the Chajnantor plateau in Chile. Credit: ESO.

ALMA is an interferometric array of sub-mm radio telescopes located on a high desert plateau in Chile. It is currently the largest ground-based astronomical project with participation from Europe, United States, Japan, Canada, South Korea, Chile and Taiwan. The location of ALMA has been chosen because the altitude and dry desert environment minimises the amount water vapour in the air column above the telescopes. One of the major science drivers of ALMA is to observe the cold universe, in particular the microwave radiation emitted by water molecules in clouds and protoplanetary disks. This radiation is however also readily absorbed by the water molecules in our own atmosphere.

ALMA consists of 66 telescopes with each telescope housing a set of receiver cartridges sensitive to different wavelength bands. NOVA, together with Onsala Observatory in Sweden and industrial partners, is constructing a total of 73 receivers for Band 5, the 163 – 211 GHz wavelength range. Within this band, the thermally excited emission of water vapour can be observed at 183 GHz.

The Band-5 receivers are heterodyne sideband-separating receivers providing vey high performance: The sensitivity is better than 75K over the whole band and better than 55K over 80% of the band. The polarisation separation is -23dB, better than any other ALMA receiver.

The production of 73 advanced astronomical instruments is somewhat atypical compared to other instrumentation projects. A mass-production approach has been taken where a dedicated team of NOVA instrument scientists and technicians assemble and test the receivers in an continuous flow. By early September 2016, 35 receivers have been delivered. The last of the 73 receivers is expected to be delivered by mid-2017.

The NOVA lead for the ALMA Band-5 project is: Dr. Wilfried Boland (NOVA).

Image below: Three ALMA Band-5 receivers ready for delivery. © NOVA.

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