Characterization of background noise and pointing direction of a sky-imager

• Grant number: 17/22170-6
• Support type: Scholarships in Brazil - Scientific Initiation
• Effective date (Start): May 01, 2018
• Effective date (End): December 31, 2018
• Field of knowledge: Physical Sciences and Mathematics - Geosciences - Meteorology
• Principal Investigator: Henrique de Melo Jorge Barbosa
• Grantee: Giovanni Souza
• Home Institution: Instituto de Física (IF). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated research grant: 13/05014-0 - GoAmazon: interactions of the urban plume of Manaus with biogenic forest emissions in Amazonia, AP.PFPMCG.TEM

Abstract

The angular distribution of sky radiance is important for the evaluation of the interaction of this radiation with complex targets, such as the human body, animals, and plants, due to their irregular shapes and complex orientations. The radiance depends both on the scattering by gas molecules as well as the scattering by aerosol particles and cloud hydrometeors. In fact, measurements of the sky radiance can be used to infer and monitor the microphysical properties of aerosols and clouds. An instrument that can perform measurements of sky radiance with high angular and temporal resolutions is an all-sky camera, as long as it has being properly calibrated. In our laboratory, we have developed a low-cost instrument that takes pictures of the sky every 5-min. It was successfully used to obtain cloud fraction in a previous IC project. The current project has two main objectives: 1) characterize, as a function of temperature, the sensor background noise; and (2) obtain the viewing angles for each pixel of the instrument (lens + camera). These are important steps towards obtaining an absolute calibration of the measured radiance and to use this data to obtain the aerosol optical properties. (AU)