World’s largest ground-based telescope opens in Chile

UK engineers are celebrating the completion of the world’s most complex ground-based telescope, which was officially opened yesterday in Chile.

The Atacama Large Millimeter/sub-millimeter Array (ALMA) is a high-frequency radio telescope made up of 66 antennas that will show never-before seen details about the birth of stars and planets and of infant galaxies from the early universe.

The antennas are spread over an area of up to 16km in diameter and will capture electromagnetic radiation with millimetre and sub-millimetre wavelengths, enabling astronomers to study the distribution of molecules that form in the space between stars.

Scientists and engineers from the UK have conducted €44m (£38m) worth of work on the international project, including development of the telescope’s cooling systems, testing of the receivers, and creating software to convert raw data into usable information.

UK project manager Prof Brian Ellison from the Rutherford Appleton Laboratory’s RAL Space said in a statement: ‘The difficulty of constructing an instrument of the scale of ALMA, and that is located in a challenging environment, should not be underestimated and it is a testament to the vision, skill and perseverance of all those involved that not only is construction complete, but early operation is producing outstanding science.’

The antennas of the ALMA array include fifty-four 12-metre and twelve smaller 7-metre dish antennas that work together as a single telescope. The 66 ALMA antennas can be arranged in different configurations, where the maximum distance between antennas can vary from 150 metres to 16 kilometres.

Each antenna collects radiation coming from space and focuses it onto a receiver. The signals from the antennas are then brought together and processed by a specialised supercomputer: the ALMA correlator.

The Technology Department at RAL was responsible for the design, manufacture and delivery of the cryostats (cooling systems) at the heart of each telescope, which each keep ten receivers at a stable temperature below -269ºC (less than 4º above absolute zero).

RAL Space also hosted and operated Europe’s Front End Integration Centre (one of three in the world), where components crucial for the receivers that detect the faint radio signals from space have been integrated and tested.

The STFC’s UK Astronomy Technology Centre (ATC) in Edinburgh provided software that scientists use to make their proposals for using ALMA valid and to turn raw data taken from observations into data cubes for studying.

The observatory was conceived as three separate projects in Europe, USA and Japan in the 1980s that merged in the 1990s.

Construction began in 2003 and the total construction cost reached approximately $1.4bn (£0.94bn), of which the European Organisation for Astronomical Research in the Southern Hemisphere (ESO) contributed just over a third.