The Hyper-Angular Rainbow Polarimeter #2 (HARP2) aboard NASA's Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) satellite is a wide-angle imaging polarimeter that measures aerosol particles and clouds, as well as properties of land and water surfaces. The amount and type of particles in suspension in the atmosphere are relevant to applications pertaining to health effects, cloud life cycle and precipitation, climate, and more. 

HARP2 combines data from multiple along-track viewing angles (up to 60), four spectral bands in the visible and near infrared ranges, and three angles of linear polarization to measure the microphysical properties of suspended atmospheric particles, including their size distribution, amount, refractive indices, and particle shape.