Infrastructure
ALMA will be a millimeter/submillimeter interferometer with 66 antennas in its initial configuration, with a possible extension in the future...
Fifty 12-meters diameter antennas will be used for interferometry*, four 12-meters diameter antennas for total power and twelve 7-meters diameter antennas for short spacings interferometry.
All the ALMA antennas will be equipped with ten frequency bands covering all atmospheric windows open from the Chajnantor site between 30GHz and 1THz.
The 12-m antennas will have reconfigurable baselines ranging from 150 m to 16 km and can be transported thanks to two transporters, Otto and Lore, specially designed to lift and move an antenna weighing 115 tons and place it on a concrete docking pad with millimetric precision.
The ability to move antennas to reconfigure the observatory's array is crucial to fulfilling ALMA's scientific missions. Indeed, changing the relative positions of the antennas and thus also the configuration of the array allows for different observing modes, comparable to using a zoom lens on a camera.
*The interferometric technique can achieve images as sharp as those of a telescope with a diameter equivalent to the distance between the 2 farthest antennas in the interferometer: more details in the glossary.
The ALMA array of antennas in the compact configuration (on the left) and in the extended configuration (on the right)
