WindCam and MSPI: two cloud and aerosol instrument concepts derived from Terra/MISR heritage

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 70.5º, 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.

Ten years of MISR observations from Terra: Looking back, ahead, and in between

“…The 10-year (and counting) MISR data record provides unprecedented opportunities for characterizing long-term trends and variability, as well as 3-D information about cloud, aerosol, and surface targets conventionally thought to be accessible only to active sensors. Technology development is underway to extend future multiangle measurements to broader spectral range (ultraviolet to thermal infrared), wider spatial swaths (enabling more rapid global coverage), and accurate polarimetric imaging [9]. Data processing approaches that take advantage of continually increasing computer speeds are also being explored to facilitate algorithm advances that were not operationally practical at the beginning of the Terra mission.…”

Evaluation and Comparison of Multi-Satellite Aerosol Optical Depth Products over East Asia Ocean

“…The AOD data accuracy of MISR is stable and superior to other sensors, which, to some degree, demonstrates the superiority of the multi-angle imaging algorithm in ocean areas. This may be because the multi-angle algorithm does not require a priori information on surface properties, making it suitable for all types of surfaces [82]. However, MISR and CALIPSO show a certain degree of negative bias in different sea areas, indicating that they both underestimate the AOD values.…”

Sensitivity analysis of polarimetric O<sub>2</sub> A-band spectra for potential cloud retrievals using OCO-2/GOSAT measurements

“…3, suggests a greater sensitivity of the angular details of I and Q to r 0 . This information is exploited by multi-angle, polarizationsensitive measurements by instruments like POLDER (Deschamps et al, 1994, Polarization and Directionality of the Earth's Reflectances;), RSP (Research Scanning Polarimeter; Cairns et al, 1999), APS (Aerosol Polarimetry Sensor; Peralta et al, 2007), MSPI (Multi-angle Spectro Polarimetric Imager; Diner et al, 2008), and the future instrument 3MI (Multi-viewing Multi-channel Multi-polarisation Imager; Manolis et al, 2013). As noted by Boesche et al (2009) and Frankenberg et al (2012), the target mode of the OCO-2 instrument could allow using the sensitivity of multiangle measurements of I and Q to r 0 through the phase matrix.…”