Far‐infrared detectors for observational cosmology

Abstract

We describe the design of a radiometer for observations of faint astronomical sources at millimeter wavelengths. The main purpose of this instrument is to make extremely sensitive measurements of the spatial distribution of the 2.7° K Cosmic Microwave Background Radiation. Important innovations in the design of this instrument are: 1) simultaneous detection of wavelengths in several bands from 2 mm to 10 mm, 2) an optical system with equal beam sizes at all wavelengths on a balloon-borne telescope platform, 3) extremely sensitive cooled bolometers with superconducting thermistors, and 4) a robust cryogenic system featuring an adiabatic demagnetization refrigerator for cooling detectors to 0.1° K in a balloon environment. These technologies are being developed by university students for future orbital applications.