ALMA observatory: See through cosmic dust
Two antennas are better than one, and 66 are definitely much better than one! By letting the antennas work together as an interferometer and varying the distance between them, a synthetic very large telescope can be created, generating images with an extraordinary quality.
The Atacama Large Millimeter Array (ALMA) is one of the world’s largest radio telescopes with 66 movable antennas. It is installed 5000 m above sea level in the Atacama Desert of Chile and observes at millimeter and submillimeter wavelengths to study star formation and the early universe.
TICRA participated in the design and validation of the ALMA telescope in a large collaboration of teams from Europe, US, and Asia. TICRA updated the design of the front end working from 84 GHz to 116 GHz and was responsible for computing the performances of all front ends in the other frequency bands. Moreover, TICRA’s engineers were in charge of the detailed analysis of the reflector antennas to account for the effects of the supporting struts, the gravity deformations and the panel misalignments.
Our reflector antenna modelling product GRASP naturally played a crucial role in the design of the antennas, as many effects can only be analysed using GRASP. Equally important, our – at the time – relatively new QUAST add-on to GRASP became very attractive for designing and analysing the front ends of the ALMA reflector antennas. QUAST is specifically developed to predict very accurately cross-polarization and sidelobe characteristics of quasi-optical systems, like the ALMA telescope operating from 30 GHz up to 1 THz.
ALMA still provides valuable science and just revealed two undiscovered galaxies heavily obscured by cosmic dust, and invisible until now to all other existing telescopes.
Image: ALMA (ESO/NAOJ/NRAO) from eso.org.