2MASS was developed to close the
gap between current technical capabilities and our knowledge of the
infrared sky. 2MASS is designed to observe at
the shortest of infrared wavelengths, the region of the electromagnetic
spectrum astronomers call the near infrared.
The two 2MASS Cassegrain-focus equatorial-mount reflector telescopes are identical in construction, and each has a primary mirror diameter of 1.3 meters. One telescope is located on Mt. Hopkins in Arizona (left), and the other on Cerro Tololo, along the Andes mountains in Chile (facility seen at right). Each telescope was equipped with a three-channel camera, each channel consisting of a 256-pixel × 256-pixel detector array, capable of observing the sky simultaneously at wavelength bands centered at wavelengths 1.25 micrometers, 1.65 micrometers, and 2.17 micrometers. (1 micrometer, abbreviated 1 µm, is one-millionth of a meter in length.) These bands are colloquially known by astronomers as "J", "H", and "K-short" (or "Ks"). The refrigerated dewar containing the camera is the brass canister hanging below the telescope. Computers operated each telescope's motion with respect to the sky; the motion of the much-smaller secondary mirror (seen near the top of the telescope); and the dark shutters of the three channels and digital "readout" of the three detector arrays.
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