Millimeter- And Submillimeter-Wave Receivers

Abstract

This review is concerned with recent developments in the design and implementation of radio-type heterodyne mixer receivers for millimeter- and submillimeter-wave astronomy. For the most part these receivers will be used for spectroscopy of the interstellar medium. Understanding of the nature of the interstellar medium has increased enormously in the last decade, in large part due to studies of interstellar molecule rotation transitions (Rank et al. 1971, Zuckerman & Palmer 1974, Thaddeus 1977). Line emission or absorption can be seen due to molecular clouds with hydrogen molecule densities ranging from 10^3-10^8 cm^(-3). This has led to improved understanding of galactic structure (Cohen et al. 1980), star formation (Elmegreen & Lada 1977), and stellar mass loss processes (Zuckerman 1980). Studies of molecule emission in external galaxies are also developing (Rickard et al. 1977). From a chemical viewpoint there has been a similar surge forward in understanding, with the identification of interstellar species such as HCO^+ (Hollis et al. 1975, Woods et al. 1975, Snyder et al . 1976) which occur in the theoretical ion-molecule reaction schemes (Herbst & Klemperer 1973, Watson 1975).