The NASA Langley High Altitude Lidar Observatory (HALO) is used to characterize distributions of greenhouse gasses, and clouds and small particles in the atmosphere, called aerosols. From an airborne platform, the HALO instrument provides nadir-viewing profiles of water vapor, methane columns, and profiles of aerosol and cloud optical properties, which are used to study aerosol impacts on radiation, clouds, air quality, and methane emissions. When the water vapor, aerosol and cloud products are combined it provides one of the most comprehensive data sets available to study aerosol cloud interactions. HALO is also configured to provide in the future measurements of the near-surface ocean, including depth-resolved subsurface backscatter and attenuation.
C-130- WFF
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).
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.
The RSP’s data archive is publicly available and organized by air campaign, each of which contain ReadMe files 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: https://data.giss.nasa.gov/pub/rsp/
A visualizer showing the times and locations of NASA Airborne Campaigns the RSP has taken part in is available at: http://rsp.apam.columbia.edu:3000
| 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 |
| Field of View | >90o |
| Instantaneous FOV | 14 mrad |
| Photodiode Detector Type: · Visible/NIR · Shortwave IR (temperature) |
Silicon HgCdTe (165K) |
| SWIR Detector Cooling | LN2 dewar |
| Data Rate | <20 kbytes/sec |
| Size, W x L x H (cm) | 40 x 64 x 34 |
| Mass (kg) | <20 |
| Power (watts) | <20 w/o heaters |
| 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 |
| Property Type | Property | Uncertainty | Reference |
|---|---|---|---|
| Aerosol | Aerosol Optical Depth for fine & coarse modes (column) | 0.02/7% | Stamnes et al., 2018 |
| Aerosol | Aerosol Size: effective radius for fine and coarse modes (column) | 0.05 µm/10% | Stamnes et al., 2018 |
| Aerosol | Aerosol Size: effective variance for fine and coarse modes (column) | 0.3/50% | Stamnes et al., 2018 |
| Aerosol | Aerosol Single Scatter Albedo (column) | 0.03 | Stamnes et al., 2018 |
| Aerosol | Aerosol Refractive Index (column) | 0.02 | Stamnes et al., 2018 |
| Aerosol | Aerosol Number Concentration | 50% | Schlosser et al., 2022 |
| Aerosol | Aerosol Top Height | < 1 km | Wu et al., 2016 |
| Aerosol | 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 | Ocean diffuse attenuation coefficient | 40% | Stamnes et al., 2018 |
| Ocean | Ocean hemispherical backscatter coefficient | 10% | Stamnes et al., 2018 |
| Cloud | Cloud Flag | 10% | |
| Cloud | Cloud Albedo | 10% | |
| Cloud | Cloud Top Phase Index | 10% | van Diedenhoven et al., 2012 |
| Cloud | Cloud Top Effective Radius | 1 um/10% | Alexandrov et al., 2012a/b |
| Cloud | Cloud Top Effective Variance | 0.05/50% | Alexandrov et al., 2012a/b |
| Cloud | Cloud Mean Effective Radius | 20% | Alexandrov et al., 2012a/b |
| Cloud | Cloud Optical Depth | 10% | Nakajima & King, 1990 |
| Cloud | Liquid Water Path | 25% | Sinclair et al., 2021 |
| Cloud | Columnar Water Vapor (Above Surface or Cloud) | 10% | Nielsen et al., 2023 (to be submitted) |
| Cloud | Cloud Top Height | 15% | Sinclair et al., 2017 |
| Cloud | Cloud Droplet Number Concentration | 25% | Sinclair et al., 2021; Sinclair et al., 2019 |
| Alexandrov, M. D., Cairns, B., & Mishchenko, M. I. (2012). Rainbow fourier transform. Journal of Quantitative Spectroscopy and Radiative Transfer, 113(18), 2521-2535. |
| Alexandrov, M. D., Cairns, B., Emde, C., Ackerman, A. S., & van Diedenhoven, B. (2012). Accuracy assessments of cloud droplet size retrievals from polarized reflectance measurements by the research scanning polarimeter. Remote Sensing of Environment, 125, 92-111. |
| 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., & King, M. D. (1990). Determination of the optical thickness and effective particle radius of clouds from reflected solar radiation measurements. Part I: Theory. Journal of Atmospheric Sciences, 47(15), 1878-1893. |
| Schlosser, J. S., Stamnes, S., Burton, S. P., Cairns, B., Crosbie, E., Van Diedenhoven, B., ... & Sorooshian, A. (2022). Polarimeter+ lidar derived aerosol particle number concentration. CHARACTERIZATION OF REMOTELY SENSED, MODELED, AND IN-SITU DERIVED AMBIENT AEROSOL PROPERTIES. |
| Sinclair, K., Van Diedenhoven, B., Cairns, B., Yorks, J., Wasilewski, A., & McGill, M. (2017). Remote sensing of multiple cloud layer heights using multi-angular measurements. Atmospheric Measurement Techniques, 10(6), 2361-2375. |
| Sinclair, K., Van Diedenhoven, B., Cairns, B., Alexandrov, M., Moore, R., Crosbie, E., & Ziemba, L. (2019). Polarimetric retrievals of cloud droplet number concentrations. Remote Sensing of Environment, 228, 227-240. |
| Sinclair, K., van Diedenhoven, B., Cairns, B., Alexandrov, M., Dzambo, A. M., & L'Ecuyer, T. (2021). Inference of precipitation in warm stratiform clouds using remotely sensed observations of the cloud top droplet size distribution. Geophysical Research Letters, 48(10), e2021GL092547. |
| Stamnes, S., et al. "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." Applied optics 57.10 (2018): 2394-2413. |
| van Diedenhoven, B., Fridlind, A. M., Ackerman, A. S., & Cairns, B. (2012). Evaluation of hydrometeor phase and ice properties in cloud-resolving model simulations of tropical deep convection using radiance and polarization measurements. Journal of the Atmospheric Sciences, 69(11), 3290-3314. |
| Wu, L., Hasekamp, O., van Diedenhoven, B., Cairns, B., Yorks, J. E., & Chowdhary, J. (2016). Passive remote sensing of aerosol layer height using near‐UV multiangle polarization measurements. Geophysical research letters, 43(16), 8783-8790. |
