In late April, a new Shortwave Spectroradiometer (SWS) began operating at the ARM Southern Great Plains (SGP) site. The instrument measures the zenith solar spectral radiance (1.4° field of view) between 300-2200 nm. The SWS incorporates two Zeiss miniature monolithic spectrometers having a spectral resolution of 8 nm in the range 300-975 nm, and 12 nm in the range 975-2200 nm. These measurements of visible and near infrared radiation will be used for testing shortwave radiation transfer models, as well as input to retrievals of cloud and aerosol properties.
As previously reported, a prototype of the new instrument—a modified version of the Solar Spectral Flux Radiometer (SSFR)—operated uninterrupted throughout a 29 day test period at the SGP site between November and December 2004. Based on the successful test period, ARM management approved the proposal to deploy a new SWS a part of the permanent instrument suite at the SGP site.
Technicians at the SGP will calibrate the instrument biweekly, using a dedicated 12-inch diameter LabSphere integrating sphere. This task involves removing the optic element from the roof port and placing it in a fixture designed to align it with the integrating sphere. To perform these routine calibrations without moving the sensitive spectrometer, SGP Site Operations staff created a “darkroom” by partitioning the east end of the SGP Optical Trailer (where the spectrometer is located) and painting it black. Development of the data collection and ingest modules is progressing