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SAM- Sun and Aureole Measurements

Visidyne's new, ground-based instrument (Patent #7693412) fills the need in a number of diverse applications for simultaneously measuring the optical depth (OD) of clouds and the forward scattering (FS) properties of their particles. Forward scattering, particularly that associated with large particles, produces the bright region surrounding the solar disk known as the aureole.

Analysis of the aureole radiance profile using an analytic solution formulated by Visidyne yields the size distribution of the scatterers. Visidyne has named the combination of two imaging cameras, a solar tracking mount, data processing software and particle scattering models, SAM (Solar Aureole Measurements). SAM sensors do not require any ancillary measurements or information other than perhaps synoptic knowledge of the scenes of interest. These sensors can provide ”truth” data to support the calibration and validation of cloud algorithms used with satellite-measured spectral radiances. SAM sensors also have important applications in cloud and climate research.


Villanucci, D., A. LePage, H. Trabucco, ..., 2008, updated weekly. "SAM (Sun and Aureole Measurements)", Burlington, MA: Visidyne, Inc. Data accessible at http://www.visidyne.com/SAM/SAM_DATA_.htm



SAM Applications

 - Climate (cloud) monitoring

 - Cloud physics research

 - Cloud algorithm cal/val

SAM Capabilities

 - Column optical depth

 - Particle size distribution

 - Column water vapor

SAM sensors can do for clouds what Aeronet sensors have done for aerosols.

An optional VIS/NIR spectrometer fitted to a SAM instrument provides coincident solar spectra from which a number of products follow. Column densities of atmospheric constituents such as water vapor and ozone can be produced from the ratios of spectral radiance. The Angstrom exponent, which is related to the size distribution of aerosols, is determined from the spectra.

Copyright 2008 - Visidyne, Inc.