The Airborne Multiangle SpectroPolarimetric Imager (AirMSPI): a new tool for aerosol and cloud remote sensing

Abstract

The Airborne Multiangle SpectroPolarimetric Imager (AirMSPI) is an eight-band (355, 380, 445, 470, 555, 660, 865, 935 nm) pushbroom camera, measuring polarization in the 470, 660, and 865 nm bands, mounted on a gimbal to acquire multiangular observations over a ± 67° along-track range. The instrument has been flying aboard the NASA ER-2 high altitude aircraft since October 2010. AirMSPI employs a photoelastic modulator-based polarimetric imaging technique to enable accurate measurements of the degree and angle of linear polarization in addition to spectral intensity. A description of the AirMSPI instrument and ground data processing approach is presented. Example images of clear, hazy, and cloudy scenes over the Pacific Ocean and California land targets obtained during flights between 2010 and 2012 are shown, and quantitative interpretations of the data using vector radiative transfer theory and scene models are provided to highlight the instrument's capabilities for determining aerosol and cloud microphysical properties and cloud 3-D spatial distributions. Sensitivity to parameters such as aerosol particle size distribution, ocean surface wind speed and direction, cloud-top and cloud-base height, and cloud droplet size is discussed. AirMSPI represents a major step toward realization of the type of imaging polarimeter envisioned to fly on NASA's Aerosol-Cloud-Ecosystem (ACE) mission in the next decade

Airborne multiangle spectropolarimetric imager (AirMSPI) observations over California during NASA's polarimeter definition experiment (PODEX)

“…The University of Maryland/Goddard Space Flight Center's Passive Aerosol and Cloud Suite (PACS) [15] employs a visible/near-infrared (VNIR) wide-angle camera that measures intensity and linear polarization over a ±55º field of view. The Jet Propulsion Laboratory's Airborne Multiangle SpectroPolarimetric Imager (AirMSPI) [16] is a gimbaled ultraviolet/VNIR pushbroom camera that acquires multiangle imagery over a ±67° along-track range. Each instrument uses a different polarization sensing approach.…”

Combined neural network/Phillips–Tikhonov approach to aerosol retrievals over land from the NASA Research Scanning Polarimeter

“…While no satellite multi-angle spectropolarimeters are currently operating, research is being carried out in the development of innovative spectropolarimetric instruments, which are currently operated on aircrafts, in view of future satellite missions. These include the Research Scanning Polarimeter (RSP, Cairns et al, 1999), the Airborne Multi-angle SpectroPolarimetric Imager (AirMSPI, Diner et al, 2013) and the Dutch instrument SPEX (van Amerongen et al, 2016). Additional spectropolarimetric missions under development are the CubeSat HyperAngular Rainbow Polarimeter (HARP) mission (Martins et al, 2014) and the Ukrainian project Aerosol-UA (Milinevsky et al, 2016).…”

The 3MI instrument on the Metop second generation

“…The Multi-angle SpectroPolarimeter Imager (MSPI) [6] as well as the SPEX instrument concept [7], offer equally powerful measurement techniques for the retrieval of polarimetric products, albeit both using a different modulation technique than that of POLDRER and 3MI (the first implementing a temporal modulation approach, while the later an innovative spectral modulation approach).…”