Solar aureole instrumentation and inversion techniques for aerosol studies.

Abstract

The in-flight calibration of satellite radiometers using ground truth measurements relies on the use of an atmospheric radiative transfer code. The accuracy of the calibration depends largely on the aerosol model used in the radiative transfer code. In order to improve the calibrations, a camera system has been developed for the determination of the aerosol size distribution, index of refraction, and scattering phase function. In addition, the camera can be used to measure ozone and water vapor content. The camera uses a two dimensional silicon CCD array to image the sun and the solar aureole. A filter wheel provides sixteen spectral bands from 380 nm to 1045 nm. The camera is mounted on an altitude-azimuth mount for tracking the sun. An external computer allows automatic or manual data acquisition. The aerosol size distribution retrieval is based on the combined inversion of solar extinction and solar aureole data. The real part of the aerosol refractive index is determined using scattering measurements in the near-backward direction, while diffuse-to-global measurements provide the imaginary part. The performance of the inversion schemes is illustrated for simulated in-flight satellite signal predictions over both high and low reflectance targets.