ABSTRACT
The principles, construction, and operation of a novel gas correlation spectrometer employing the Zeeman effect to perform selective modulation are described. The retrieval of column amounts of atmospheric nitric oxide (NO) is discussed. The sun is used as an IR source, and the radiation is modulated by the splitting of absorption lines in a sample of NO gas which is positioned in a variable longitudinal field. A sample of the results obtained at a high altitude observatory is presented. The diurnal variation in the observed NO column is consistent with photochemical predictions. Unexpected shorter term variabilities which are observed may be dynamic effects but are more likely to be instrumental artifacts. The instrument is insensitive to tropospheric NO, making it potentially useful for long term monitoring from the ground of NO in the stratosphere and mesosphere.
ABSTRACT
The pressure-modulated CO(2) radiometer is a new kind of instrument capable of making temperature soundings in the 40-80-km region of the earth's atmosphere. It is intended to be mounted on a polar-orbiting satellite, where it will give global coverage of the upper atmosphere in a region that is not well understood at present but that is, as rocket soundings show, clearly the seat of many interesting and vigorous phenomena. The new technique employs a cell containing carbon dioxide as a filter. The pressure and hence transmission of this cell is periodically modulated, resulting in the selection of thermal radiation from the strong lines in the spectrum of atmospheric CO(2). This radiation originates at levels in the atmosphere where the pressure is low. The energy grasp of the device is large enough to give high sensitivity. Tests with a laboratory prototype and a balloon-borne instrument show that the device, if mounted outside the atmosphere, could detect changes of around 1 K in the temperature at 65-km altitude.
