Design and characterization of specMACS, a multipurpose hyperspectral cloud and sky imager

Abstract

Abstract. The new spectrometer of the Munich Aerosol Cloud Scanner (specMACS) is a multipurpose hyperspectral cloud and sky imager designated, but not limited to investigations of cloud-aerosol interactions in Earth's atmosphere. Equipped with a high spectral and spatial resolution, the instrument is designed to measure solar radiation in the visible and short-wave infrared region that is reflected from, or transmitted through clouds and aerosol layers. It is based on two hyperspectral line cameras that measure in the solar spectral range between 400–2500 nm with a spectral bandwidth between 2.5–12.0 nm. The instrument was already operated in ground-based campaigns as well as aboard the German High Altitude LOng Range (HALO) research aircraft, e.g. during the ACRIDICON-CHUVA campaign in Brazil during summer 2014. This paper describes the specMACS instrument hardware and software design and characterizes the instrument performance. During the laboratory characterization of the instrument the radiometric response as well as the spatial and spectral performance was assessed. Since the instrument is primarily intended for retrievals of atmospheric quantities by inversion of radiative models using measured radiances, a focus is placed on the determination of its radiometric response. Radiometric characterization was possible for both spectrometers with an absolute accuracy of 3 % at their respective central wavelength regions. First measurements are presented which demonstrate the application possibilities and show that the key demands on radiometric and spectral accuracy as posed by the intended remote sensing techniques are fulfilled.