GISS Research Scanning Polarimeter

Photopolarimetry Measurements of Aerosols

Photo of the RSP device with a cooling dewar and the scanning system attached to a central mount

The NASA GISS Research Scanning Polarimeter (RSP) is a passive, downward-facing polarimeter that makes total radiance and linear polarization measurements in nine spectral bands ranging from the visible/near-infrared (VNIR) to the shortwave infrared (SWIR). The band centers are: 410 (30), 470 (20), 550 (20), 670 (20), 865 (20), 960 (20), 1590 (60), 1880 (90) and 2250 (130) nm where the full width at half maximum (FWHM) bandwidths of each channel is shown in parenthesis. Noise is minimized in the SWIR channels by cooling the detectors to less than 165K using a dewar of liquid nitrogen. The RSP measures the degree of linear polarization (DoLP) with an uncertainty of < 0.2%. The polarimetric and radiometric intensity measurement uncertainties are each < 3%. A full set of RSP's design parameters are shown in Table 1 and more details on design and calibration can be found in Cairns et al. (1999) and Cairns et al. (2003).

Table 1: RSP Design Parameters
Parameter Performance
Degree of Linear Polarization Uncertainty (%) < 0.2
Polarization Uncertainty (%) < 3.0
Radiometric Uncertainty (%) < 3.0
Dynamic Range > 104
Signal-to-Noise Ratio > 2000 (with R=0.3)
Spectral Characteristics See Table 2 below
Field of View > 90°
Instantaneous FOV 14 mraa
Photodiode Detector Type:
 * Visible/NIR
 * Shortwave IR (temperature)
HgCdTe (165K)a
SWIR Detector Cooling LN2 dewar
Data Rate < 20 kbytes/sec
Size, W×L×H (cm) 40×64×34
Mass (kg) < 20
Power (watts) < 20 w/o heaters
Table 2: RSP Spectral Characteristics
Band ID λc (nm) Δλ (nm) Wavelength Type
V1 410 27 Visible
V2 470 20 Visible
V3 555 20 Visible
V4 670 20 Visible
V5 865 20 Near-IR
V6 960 20 Near-IR
S1 1590 60 Shortwave-IR
S2 1880 90 Shortwave-IR
S3 2250 130 Shortwave-IR

The RSP is an along track scanning instrument that can make up to 152 measurements sweeping ±60° from nadir along the aircraft's track every 0.8 seconds with each measurement having a 14 mrad (∼0.8°) field-of-view. Each scan includes stability, dark reference and calibration checks. As the RSP travels aboard an aircraft, the same nadir footprint is viewed from multiple angles. Consecutive scans are aggregated into virtual scans that are reflectances of a single nadir footprint from multiple viewing angles. This format comprises the RSP's Level 1C data.

RSP's high-angular resolution and polarimetric accuracy enables numerous aerosol, cloud and ocean properties to be retrieved. These are Level 2 data products. A summary of the primary L2 aerosol, cloud and ocean data products retrieved by the RSP are shown in Table 3.

Table 3: Summary of L2 Data Products
Property Type Property Uncertainty Reference
Aerosol Aerosol Optical Depth for fine & coarse modes (column) 0.02/7% Stamnes et al., 2018
Aerosol Size: effective radius for fine and coarse modes (column) 0.05 µm/10% Stamnes et al., 2018
Aerosol Size: effective variance for fine and coarse modes (column) 0.3/50% Stamnes et al., 2018
Aerosol Single Scatter Albedo (column) 0.03 Stamnes et al., 2018
Aerosol Refractive Index (column) 0.02 Stamnes et al., 2018
Aerosol Number Concentration 50% Schlosser et al., 2022
Aerosol Top Height < 1 km Wu et al., 2016
Surface Wind Speed 0.5 m s-1 Stamnes et al., 2018
Ocean Chlorophyll-A Concentration 0.7 mg m-3 Stamnes et al., 2018
Ocean diffuse attenuation coefficient 40% Stamnes et al., 2018
Ocean hemispherical backscatter coefficient 10% Stamnes et al., 2018
Cloud Cloud Flag 10%  
Cloud Albedo 10%  
Cloud Top Phase Index 10% van Diedenhoven et al., 2012
Cloud Top Effective Radius 1 µm/10% Alexandrov et al., 2012a/b
Cloud Top Effective Variance 0.05/50% Alexandrov et al., 2012a/b
Cloud Mean Effective Radius 20% Alexandrov et al., 2012a/b
Cloud Optical Depth 10% Nakajima & King, 1990
Liquid Water Path 25% Sinclair et al., 2021
Columnar Water Vapor (Above Surface or Cloud) 10%  
Cloud Top Height 15% Sinclair et al., 2017
Cloud Droplet Number Concentration 25% Sinclair et al., 2021; Sinclair et al., 2019

Data Downloads

The RSP's data archive is publicly available and organized by air campaign, each of which contains a README file provided by the RSP team for their Level 1C and Level 2 data products, including important details about biases and uncertainties that data users should consult. The RSP data archive is available at

Campaign Visualizer

A visualizer showing the times and locations of NASA Airborne Campaigns the RSP has taken part in is available at


Recent campaigns the RSP has taken part in include:

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Alexandrov, M.D., B. Cairns, and M.I. Mishchenko, 2012: Rainbow Fourier transform. J. Quant. Spectrosc. Radiat. Transfer, 113, 2521-2535, doi:10.1016/j.jqsrt.2012.03.025.

Alexandrov, M.D., B. Cairns, C. Emde, A.S. Ackerman, and B. van Diedenhoven, 2012: Accuracy assessments of cloud droplet size retrievals from polarized reflectance measurements by the research scanning polarimeter. Remote Sens. Environ., 125, 92-111, doi:10.1016/j.rse.2012.07.012.

Cairns, B., E.E. Russell, and L.D. Travis, 1999: The Research Scanning Polarimeter: Calibration and ground-based measurements. In Polarization: Measurement, Analysis, and Remote Sensing II, 18 Jul. 1999, Denver, Col., Proc. SPIE, vol. 3754, pp. 186, doi:10.1117/12.366329.

Cairns, B., E.E. Russell, J.D. LaVeigne, and P.M.W. Tennant, 2003: Research scanning polarimeter and airborne usage for remote sensing of aerosols. In Polarization Science and Remote Sensing, 3 Aug. 2003, San Diego, Cal., Proc. SPIE, vol. 5158, pp. 33, doi:10.1117/12.518320.

Nakajima, T., and M.D. King, 1990: Determination of the optical thickness and effective particle radius of clouds from reflected solar radiation measurements. Part I: Theory. J. Atmos. Sci., 47, no. 15, 1878-1893, doi:10.1175/1520-0469(1990)047<1878:DOTOTA>2.0.CO;2.

Schlosser, J.S., S. Stamnes, S.P. Burton, B. Cairns, E. Crosbie, B. Van Diedenhoven, G. Diskin, S. Dmitrovic, R. Ferrare, J.W. Hair, C.A. Hostetler, Y. Hu, X. Liu, R.H. Moore, T. Shingler, M.A. Shook, K.L. Thornhill, E. Winstead, L. Ziemba, and A. Sorooshian, 2022: Polarimeter + lidar-derived aerosol particle number concentration. Front. Remote Sens., 3, 885332, doi:10.3389/frsen.2022.885332.

Sinclair, K., B. van Diedenhoven, B. Cairns, J. Yorks, A. Wasilewski, and M. McGill, 2017: Remote sensing of multiple cloud layer heights using multi-angular measurements. Atmos. Meas. Tech., 10, 2361-2375, doi:10.5194/amt-10-2361-2017.

Sinclair, K., B. van Diedenhoven, B. Cairns, M. Alexandrov, R. Moore, E. Crosbie, and L. Ziemba, 2019: Polarimetric retrievals of cloud droplet number concentrations. Remote Sens. Environ., 228, 227-240, doi:10.1016/j.rse.2019.04.008.

Sinclair, K., B. van Diedenhoven, B. Cairns, M. Alexandrov, A. Dzambo, and T. L'Ecuyer, 2021: Inference of precipitation in warm stratiform clouds using remotely sensed observations of the cloud top droplet size distribution. Geophys. Res. Lett., 48, no. 10, e2021GL092547, doi:10.1029/2021GL092547.

Stamnes, S., C. Hostetler, R. Ferrare, S. Burton, X. Liu, J. Hair, Y. Hu, A. Wasilewski, W. Martin, B. van Diedenhoven, J. Chowdhary, I. Cetinic, L. Berg, K. Stamnes, and B. Cairns, 2018: Simultaneous polarimeter retrievals of microphysical aerosol and ocean color parameters from the "MAPP" algorithm with comparison to high spectral resolution lidar aerosol and ocean products. Appl. Opt., 57, no. 10, 2394-2413, doi:10.1364/AO.57.002394.

Van Diedenhoven, B., A.M. Fridlind, A.S. Ackerman, and B. Cairns, 2012: Evaluation of hydrometeor phase and ice properties in cloud-resolving model simulations of tropical deep convection using radiance and polarization measurements. J. Atmos. Sci., 69, 3290-3314, doi:10.1175/JAS-D-11-0314.1.

Wu, L., O. Hasekamp, B. van Diedenhoven, B. Cairns, J.E. Yorks, and J. Chowdhary, 2016: Passive remote sensing of aerosol layer height using near-UV multi-angle polarization measurements. Geophys. Res. Lett., 43, no. 16, 8783-8790, doi:10.1002/2016GL069848.