Synonyms: 
ER-2
Associated content: 
ER-2 - AFRC
Sub-categories: 
ER-2 #806, ER-2 #809

Reactive Nitrogen

Instrument: Reactive Nitrogen

Principal Investigator: David W. Fahey

Organization:
NOAA Aeronomy Laboratory
325 Broadway,R/E/AL6
Boulder, CO 80303

Principle of Operation:
The instrument is designed to measure nitric oxide (NO) and the sum of reactive nitrogen oxides (NOy). Species included in NOy are NO, NO2, HNO3, N2O5 and ClONO2. NO is measured by detecting light from the chemiluminescent reaction between reagent ozone and NO in the ambient sample. NOy is reduced to NO by catalytic reduction on a gold surface with carbon monoxide (CO) acting as a reducing agent. The catalyst is located outside the aircraft fuselage in order to avoid inlet line losses. Two reaction vessels are incorporated in the instrument to allow for simultaneous measurement of NO and NOy. Ca1ibration with NO or NO2 is made by standard addition several times during a flight. The baseline of each measurement is determined in part by the addition of synthetic air that contains no reactive nitrogen. The difference between the sample flow velocity in the inlet opening and the aircraft velocity cause aerosol particles in the atmosphere to be oversampled. For sizes below 5 micrometers in diameter, this feature assists in the identification of aerosol particles that contain NOy.

 

 

Accuracy: < 20% plus precision
Detection limit: < 0.1 ppbv NOy, ~0.02 ppbv NO
Response time: 1 sec
Location on the ER2: Lower Q-bay rack

Reference: D.W. Fahey et al., In situ aerosol measurements of total reactive nitrogen, total water, and aerosol in a polar stratospheric cloud in the Antarctic, J. Geophys. Res. 94 11-99-11315, 1959.

Measurements: 
NO2, NO3, NOy, NO, N2O5, ClONO2
Aircraft: 
ER-2 - AFRC
Point(s) of Contact: 
David Fahey (PI)

Research Scanning Polarimeter

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
 

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
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

 

Table 2: RSP Spectral Channels
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

 

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 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

 

Table 4: References
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.
Instrument Type: 
Polarimeter
Measurements: 
Imagery
Aircraft: 
ER-2 - AFRC, P-3 Orion - WFF, C-130- WFF, King Air B-200 - LaRC, J-31
Point(s) of Contact: 
Brian Cairns (PI)

Enhanced MODIS Airborne Simulator

The Enhanced MODIS Airborne Simulator (EMAS) is a multispectral scanner configured to approximate the Moderate-Resolution Imaging Spectrometer (MODIS), an instrument orbiting on the NASA Terra and Aqua satellites. MODIS is designed to measure terrestrial and atmospheric processes. The EMAS was a joint development project of Daedalus Enterprises, Berkeley Camera Engineering, the USU Space Dynamics Laboratory, and Ames Research Center. The EMAS system acquires 50-meter spatial resolution imagery, in 38 spectral bands, of cloud and surface features from the vantage point of the NASA ER-2 high-altitude research aircraft.

Instrument Type: Multispectral Imager
Measurements: VNIR/SWIR/LWIR Imagery
 

Instrument Type: 
Spectrometer
Measurements: 
Imagery
Aircraft: 
ER-2 - AFRC
Point(s) of Contact: 
Steve Platnick (Co-I)

HIAPER Airborne Radiation Package

The HIAPER Airborne Radiation Package (HARP) instrumentation is a comprehensive atmospheric radiation suite to measure spectrally resolved actinic flux and horizontally stabilized irradiance. HARP was developed in a collaborative effort between NCAR, the University of Colorado, the Leibniz-Institute for Tropospheric Research, Metcon, Inc and Enviscope GmbH. The package is part of the HIAPER Aircraft Instrumentation Solicitation (HAIS), funded by NSF.

Instrument Type: 
Radiometer
Measurements: 
Actinic Flux, Irradiance
Aircraft: 
Gulfstream V - NSF, C-130 - NSF, ER-2 - AFRC
Point(s) of Contact: 
Samuel R. Hall (PI)

Harvard Halogen Instrument

Many changes from the original Chlorine Nitrate instrument. NO2 instrument removed. New inlet with orifice for one halogen duct, addition of vacuum scroll pump, new RF oscillators and amplifiers, new RF frequency, new lamp housings and cooling for lamp modules. Flew in MACPEX without dissociation heaters, i.e., focus on BrO and ClO measurements and not measure ClONO2 or ClOOCl.

Instrument Type: 
Fluorescence
Measurements: 
BrO, ClO, CIONO2
Aircraft: 
WB-57 - JSC, ER-2 - AFRC
Point(s) of Contact: 
David Wilmouth (PI)

Advanced Whole Air Sampler

32 samples/flight (ER-2); 50 samples/flight (WB57); 90 samples/flight (Global Hawk)

Updated control system with remote control capability

Fill times
–14 km 30 – 40 sec
–16 km 40 – 50 sec
–18 km 50 – 60 sec
–20 km 100 – 120 sec (estimated)

Analysis in UM lab: GC/MS; GC/FID; GC/ECD

Instrument Type: 
Whole Air Sampling
Measurements: 
CFCs, HFCs, HCFCs, Halons, Solvents, VSLS, NMHCs, Organic Nitrates, CO, CH4, N2O
Aircraft: 
Global Hawk - AFRC, ER-2 - AFRC, WB-57 - JSC
Point(s) of Contact: 
Elliot Atlas (PI)

Cloud Lidar System

The CLS is flown on the ER-2 to conduct cloud radiation and severe storm field experiments. Designed to operate at high altitudes in order to obtain measurements above the highest clouds, the instrument provides the true height of cloud boundaries and the density structure of less dense clouds. The height structure of cirrus, cloud top density and multiple cloud layers may also be profiled. The system specifications are as follows:

Laser Type: Nd:YAG I,II
Wavelength: 1064, 532 nanometer
Pulse Energy: 90, 30 mJ
Pulse repetition frequency: 10 Hz
Beam width: 1 mrad

Diameter: 0.15 m
Beam width: 1.4 mrad
Polarization: vert. and horiz.

Sample rate: Measurements at 20 m intervals at 200 m/s aircraft speed
Range Resolution: 7.5 m
Number of Channels: 4
Samples per Channel: 3310
Record Capacity: 8 hours

Instrument Type: 
Lidar
Measurements: 
Cloud Thickness
Aircraft: 
ER-2 - AFRC
Point(s) of Contact: 
James Spinhirne (PI)

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