Design, construction, and testing of a microprocessor controlled tracking and scanning solar spectroradiometer

Abstract

A versatile solar spectroradiometer has been designed which is capable of measuring direct solar radiation, the solar aureole, and sky radiance far from the sun. An active tracker consisting of a quadrant detector, telescope and stepper-motor driven alt-azimuth mount is used to position the spectroradiometer by computer control for solar tracking and almucantur scans. An internally baffled telescope designed to suppress stray light is employed as the optical receiver, and a photodiode serves to convert the collected flux to an electrical signal. A digitally controlled gain-switching transimpedance amplifier is used to scale the photodiode output to accommodate the large signal range encountered between measuring direct solar radiation and sky radiance well away from the sun. Example measurements are presented which demonstrate the system's capabilities.