Submillimeter-wave atmospheric and astrophysical spectroscopy

The paper describes the results and methods of work which has been in progress during the past five years at the U.K. National Physical Laboratory and Queen Mary College, London on the submillimeter spectrum and its application to atmospheric and astrophysical problems. The paper begins with descriptions of the spectroscopic techniques evolved and used, which provide spectral resolution more than half an order of magnitude finer than previously available, particularly at the lower frequency end of the range, from 15 cm(-1) to 25 cm(-1). Excellent signal-to-noise ratios and reproducibility have been obtained and applied as shown in the second part of the paper to both atmospheric studies (chiefly at NPL) and astrophysical problems (chiefly at QMC). The former are illustrated with aircraft-borne measurements of minor species, such as H(2)O, O(3), HNO(3), and other gases, the latter with a consideration of the cosmic background at submillimeter wavelengths. A common thread is provided by developments in observational and interpretational spectroscopic techniques needed to overcome problems peculiar to this region of the spectrum. Our current progress in understanding the region and also prospects for future submillimeter spectroscopy are each brought into review in this work.