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HARP2 Polarimeter

HARP2 (Hyper-Angular Rainbow Polarimeter #2) is a wide angle imaging polarimeter designed to measure 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, etc. HARP2 will combine 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 the atmospheric particles including their size distribution, amount, refractive indices and particle shape.

HARP2 is a contributed instrument to the PACE mission, designed and built by UMBC's Earth and Space Institute.

HARP2 Heritage

HARP2 is preceded by its aircraft version (AirHARP) and by the HARP 3U CubeSat satellite that was successfully launched from the International Space Station on 19-Feb-2020 (learn more at the UMBC website). The three current versions of HARP uses the same basic telescope and optical system to measure polarization in the visible and near infrared (VNIR) spectral ranges.

The AirHARP instrument has flown on the NASA ER2 aircraft during the ACEPOL (Aerosol Characterization from Polarimeter and Lidar) campaign and on the NASA UC12 aircraft during the LMOS (Lake Michigan Ozone Study). AirHARP data has been used for algorithm development to demonstrate the science proposed for the HARP2 instrument on the retrieval of aerosol and cloud properties.
HARP2 Overview
9.6 kg (21.2 lb), current best estimate.
11.5 W, current best estimate.
316 x 355 x 440 mm, current best estimate.
94° cross track; +/- 57° along track.
60 along track viewing angles for the 669 nm band; 10 along track viewing angles for the other 3 bands (441, 549, and 873 nm)
2 days global coverage at 2.6 km (1.62 miles) resolution.
Center wavelengths: 441, 549, 669, 873 nm; Bandwidths: 15, 12, 16 and 43 nm.
0°, 45° and 90°.
Polarization accuracy <1%. Monthly lunar and solar calibrations. Cross calibration with OCI and SPEXOne instruments; Internal flat field calibrator to extend calibrations over the whole field of view.
AirHARP Instrument in the NASA ER2 Aircraft
The AirHARP instrument integrated to the wing super-pod of the NASA ER2 aircraft
The AirHARP instrument integrated to the wing super-pod of the NASA ER2 aircraft, as it was flown during the NASA ACEPOL aircraft campaign.
Data collected during ACEPOL over fires in Arizona
Data collected during ACEPOL over fires in Arizona. The degree of polarization (DoLP) image shows the effect of the fresh smoke on the polarization field illustrating the information contained on polarization measurements. The RGB image on the right hand side shows a true color reconstruction of one of the HARP viewing angles over the scene.