The Chajnantor Test Facility

The Chajnantor Test Facility, operated by Caltech in collaboration with the University of Chile and the University of Concepción, is located at an elevation of 5080 meters (16700 feet) in the Andes mountains of northern Chile. The high, dry Chajnantor plateau is one of the best sites in the world for millimeter and submillimeter astronomy. The unique location of the observatory enables very-sensitive measurements of the polarization of the CMB, opening a new window into the early universe.

Current observations at Chajnantor are focused around the QUIET project. The Q/U Imaging Experiment (QUIET) started making observations of the polarization of the cosmic microwave background radiation in October 2008. A collaboration between experimental groups at Caltech, Chicago, Columbia, JPL, KEK, Manchester, MPI Bonn, Miami, Oslo, Oxford, Princeton, and Stanford, QUIET is a program to make very-sensitive measurements of the polarization of the cosmic microwave background with large arrays of coherent correlation polarimeters. QUIET takes advantage of a breakthrough developed at JPL for the packaging of the polarimeters ("radiometer on a chip") that allows their mass production so that thousands of detectors can be used. In the first phase, two receivers have been constructed, one with 19 pixels at 44 GHz and another with 91 pixels at 90 GHz. A 1.4m compact range antenna is attached to the CBI mount. The measurements cover angular scales from a few arc minutes to several degrees.

The Chajnantor Test Facility represents a great opportunity for Caltech astronomy students from both observational and instrument building perspectives. The new radio lab in Cahill is developing and testing more sensitive detectors to be used in these radiometers.

Text maintained by Walter Max-Moerbeck <wmax [at]>