Abstract
The Multi-angle Imaging SpectroRadiometer (MISR) has been acquiring global cloud and aerosol data from polar orbit
since February 2000. MISR acquires moderately high-resolution imagery at nine view angles from nadir to 70.5°, in four
visible/near-infrared spectral bands. Stereoscopic parallax, time lapse among the nine views, and the variation of
radiance with angle and wavelength enable retrieval of geometric cloud and aerosol plume heights, height-resolved
cloud-tracked winds, and aerosol optical depth and particle property information. Two instrument concepts based upon
MISR heritage are in development. The Cloud Motion Vector Camera, or WindCam, is a simplified version comprised
of a lightweight, compact, wide-angle camera to acquire multiangle stereo imagery at a single visible wavelength. A
constellation of three WindCam instruments in polar Earth orbit would obtain height-resolved cloud-motion winds with
daily global coverage, making it a low-cost complement to a spaceborne lidar wind measurement system. The
Multiangle SpectroPolarimetric Imager (MSPI) is aimed at aerosol and cloud microphysical properties, and is a
candidate for the National Research Council Decadal Survey's Aerosol-Cloud-Ecosystem (ACE) mission. MSPI
combines the capabilities of MISR with those of other aerosol sensors, extending the spectral coverage to the ultraviolet
and shortwave infrared and incorporating high-accuracy polarimetric imaging. Based on requirements for the nonimaging
Aerosol Polarimeter Sensor on NASA's Glory mission, a degree of linear polarization uncertainty of 0.5% is
specified within a subset of the MSPI bands. We are developing a polarization imaging approach using photoelastic
modulators (PEMs) to accomplish this objective.
