Some of the ALMA telescope's 66 antennas, soon to be supplied with new receivers developed and designed at Chalmers. Credit: ESO / B. Tafreshi.
In April 2020 a long-awaited contract was signed to begin production of a new set of receivers for ALMA, the Atacama Large Millimetre / Submillimetre Array. The signing marks the start of a major project whose products require extreme precision and performance, something that only a few research groups in Europe can take on. As a partner in the ALMA telescope, the European astronomy organization ESO will have a supervisory role in the production.
Many of the most significant astronomical observations in recent years have been carried out using the ALMA telescope, for example the first image of a black hole, released in 2019. ALMA consists of 66 interconnected radio antennas that together observe the universe at different frequencies from a high plateau in the Atacama desert in Chile. The telescope studies the light from some of the universe's coldest bodies. ALMA is sensitive to light that is invisible to human eyes, with wavelengths around one millimeter, between infrared light and microwaves.
The new contract is not the first time that GARD has been commissioned to design and manufacture receivers for the instrument.
– We had the privilege of being involved in developing the telescope’s most recent new receivers, in a project that was ongoing between 2010 and 2018. Our goal this time is the same, to make the best possible receiver for the frequency range. An optimal instrument, in other words, says Victor Belitsky.
Each of ALMA's 66 dish antennas has a suite of receivers which each cover in a sharply defined frequency range, or "band". The latest complete set of receivers that GARD delivered were for Band 5 (read more in news item "Receivers from Chalmers will image the distant universe
"). Those receivers are now being used to search for water in our solar system and in the Milky Way. They are also giving scientists new insights into how stars, planets and galaxies are born.
The frequency range that the new receivers will open up is known as Band 2. In this band, ALMA can study gas and radiation in the tenuous, cold environment between stars, which scientists call the interstellar medium. New studies of other astronomical phenomena inside and outside the Milky Way, such as planetary disks and distant galaxies, will also become possible.
– Technology for developing receivers and amplifiers has been progressing fast. The great thing with these new instruments is that they can receive signals over a wider frequency range than previous receivers. This means, for instance, that you can observe different properties of the same object, without having to recalibrate the instruments between the observations. That's a big advantage, explains Victor Belitsky.
For Victor Belitsky and his GARD team, a pre-production phase has just started after approval by the ALMA Committee, following their participation in the design and successful testing of a prototype (see image). The pre-production phase, which is expected to take about 2.5 years, includes the development and production of six complete "cartridges" that include receivers and signal amplifiers. Once produced and approved, colleagues in Italy and the Netherlands will then manage the production of cartridges for each antenna.
– Our group’s talents are best suited to the development and design phases, and we prefer to focus on those parts. Instead of creating a "production line" and producing many similar instruments, we will move on towards new development projects. But of course we will be available to contribute knowledge and expertise during the production phase as well, says Victor Belitsky.
Susanne Aalto, professor of radio astronomy at Chalmers, is enthusiastic about ALMA's future possibilities.
– With Band 2, ALMA further expands its window towards the invisible, "cold" universe. Among other things, we have new opportunities to study the properties of very young, distant galaxies in order to be able to map out how they evolve. This new window also allows us to study really dense and cold gas in more nearby galaxies to understand how massive bursts of star formation can occur and how supermassive black holes grow.
– We also get access to new lines, new molecules and new chemistry to study the life cycle of stars and planets in our own galaxy, the Milky Way. For example, we can study how large grains of dust evolve and grow to eventually form planets, she says.
Text: Christian Löwhagen.
Image 1: Some of the ALMA telescope's 66 antennas, soon to be supplied with new receivers developed and designed at Chalmers. Credit: ESO / B. Tafreshi.
Image 2: The prototype for ALMA's new Band 2 receiver. The receiver contains a horn antenna, polarization splitter, amplifier and waveguide. As a cryogenic receiver, it will be cooled down to about 10 degrees above absolute zero (10 K or -263 degrees Celsius). The prototype has been designed by GARD at Chalmers and built at the Italian National Institute of Physics, INAF.
More about GARD
More about Band 2
The production of the Band 2 receiver cartridges will be undertaken by a consortium comprising the Netherlands Research School for Astronomy (NOVA), Chalmers University, Gothenburg, Sweden, and the Italian National Institute for Astrophysics (INAF). The National Astronomical Observatory of Japan (NAOJ) will contribute to the production and testing of receiver optics as an East Asia contribution to the ALMA Development Program. The National Radio Astronomy Observatory (NRAO) and the University of Chile have been involved in the development and production of some components of the receivers, which will be sent to ESO for testing and integration.
More about ALMA
ALMA, an international astronomy facility, is a partnership of ESO, the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile.