ER-2 809
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Condensation Nucleus Counters (CNCs) and Electrical Aerosol Sampler (EAS)

Instrument: Condensation Nucleus Counters (CNCs) and

Electrical Aerosol Sampler (EAS)

Principal Investigator: James C. Wilson

University of Denver
Department of Engineering
2390 S. York Street
Denver, CO 80208

Instrument Description:
Two condensation nucleus counters (CNCs) have been developed for use on the NASA ER-2 high altitude research aircraft. One CNC measures the number concentration of aerosol particles having diameters in the 0.01 to about 1.0 micron range, while the second uses a heated (150 oC) inlet to vaporize volatile components and then measures the number concentration of residue particles. Used together, the CNCs discriminate between particles composed of volatile materials (i.e., sulfuric acid), and those containing components that are non-volatile at temperatures of 150 oC. For SPADE, the CNCs should be able to distinguish between particles containing carbon soot (an aircraft exhaust product) and background sulfate particles.

Two aerosol collectors have been developed for the SPADE mission. The first uses electrical precipitation to collect particles with diameters greater than 0.01 microns on electron microscope grids. Similar samples, but of particles with diameters greater than about 0.1 microns, are taken concurrently with an impactor. The sealed samples are then returned to the laboratory for analysis by analytical electron microscopy. Up to 25 samples may be collected by each method during a single flight.

Instrument Function: The CNCs function by saturating an aerosol sample with warm alcohol vapor and then cooling the sample so that the alcohol vapor condenses on the particles. The particles grow by vapor deposition to a size such that the individual particles are easily detected by a simple optical particle counter.

The aerosol collectors function by two different principles. In the electrical collector, a needle is forced into a corona discharge by high voltage. The sample is carried past the corona point, and unipolar ions produced by the corona attatch to the particles, causing them to become charged. The charged particles are then collected on a grounded electron microscope grid. In the impactor, the air sample is accelerated through a nozzle and forced around a sharp bend. Particles larger than about 0.1 micron diameter cannot follow the streamlines and instead impact onto an electron microscope grid located at the bend.

Accuracy: The accuracy and precision of the CNCs is highly dependent on the aerosol size distribution. For aerosols whose number distribution is dominated by particles larger than 0.01 microns in diameter, the submicron number concentration is usually measured with an uncertainty of less than 20% and a precision smaller than 10%.

Reference: Wilson, James Charles, Edmund D. Blackshear and Jong Ho Hyun. "The Function and Response of an Improved Stratospheric Condensation Nucleus Counter." J. Geophys. Res. 88 (1983): 6781-6785.

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Multiple Axis Resonance Fluorescence Chemical Conversion Detector for ClO and BrO

Vacuum ultraviolet radiation produced in a low pressure plasma discharge lamp is used to induce resonance scattering in Cl and Br atoms within a flowing sample. ClO and BrO are converted to Cl and Br by the addition of NO such that the rapid bimolecular reaction ClO + NO → Cl + NO2 (BrO + NO → Br + NO2) yields one halogen atom for each halogen oxide radical present in the flowing sample. Three detection axes are used to diagnose the spatial (and thus temporal) dependence of the ClO (BrO) to Cl (Br) conversion and to detect any removal of Cl (Br) following its formation. A double duct system is used both to maintain laminar flow through the detection region and to step the flow velocity in the detection region down from free stream (200 m/sec) to 20 m/sec in order to optimize the kinetic diagnosis.

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Lyman Alpha-Hygrometer


Instrument: Lyman Alpha-Hygrometer

Principal Investigator: Ken Kelly

NOAA/ERL/Aeronomy Laboratory
325 Broadway MS R/E/AL6
Boulder, CO 80303

Principle of Operation: A 121.6 nm light source dissociates a fraction of the water and forms excited hydroxyl radicals. These radicals will either fluoresce at 309 nm or be quenched by air molecules. A PMT measures the 309 nm light, which is proportional to the water vapor mixing ratio. A photodiode monitors the 121.6 nm intensity at the same distance as the sample chamber center. An in-flight calibration is obtained from the measured absorption of 121.6 nm light by injected water vapor, the known absorption cross section and the chamber pressure. The hygrometer will measure total water.

Accuracy: 6%
Detection Limit: 0.1 ppmv
Response Time: 1 Second
Location on ER-2: Q-Bay

Reference: Kley, D., A. Schmeltekopf, K. Kelly, R. Winkler, T. Thompson, M. McFarland. "The U-2 Lyman-Alpha results from the 1980 Panama Experiment." The 1980 Stratospheric-Tropospheric Exchange Experiment. Ed: A.P.Margozzi. NASA Technical Memo 84297 (1983): 85-125.



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FSSP-300 Aerosol Spectrometer

Instrument: FSSP-300 Aerosol Spectrometer


Principal Investigator: Guy V. Ferry



NASA-Ames Research Center

M.S. 245-5

Moffett Field, CA 94035-1000


Principal Investigators: James E. Dye (303) 497-8944 Darrel Baumgardner (303) 497-1054 FAX (303) 497-8181 Organization: National Center for Atmospheric Research 1850 Table Mesa Drive Boulder, Co 80307 Principle of Operation: The Forward Scattering Spectrometer Probe (FSSP) Model 300 sizes particles by measuring the amount of laser light scattered from angles of 4 to 12&degree; by aerosol particles in situ as they pass through a focused laser beam. Comparison of voltage outputs from the signal detector and a masked slit detector is used to electro-optically define the sample area. Fig. 1 shows the configuration of the instrument. The instrument system is composed of two parts: (l) a Particle Measuring Systems model FSSP-300 aerosol spectrometer, and (2) a data acquisition and recording system. The FSSP-300 aerosol spectrometer is located on the front of the starboard spear pod of the ER-2. The data acquisition and recording system is part of the package that houses the FPCAS aerosol spectrometer located in the bottom, rear portion of the starboard spear pod of the ER-2. The FSSP-300 aerosol spectrometer sizes particles in the 0.4 to 20 micron diameter size range (depending on the refractive index of the aerosol particles measured) in the free air stream outside the ER-2. The measured particles are divided into 31 size intervals with more resolution at smaller sizes.


Detection Limit: 0.4 to 20 micrometers diameter Sampling Rate: 0.1 Hertz Location on ER-2: Nose of right pod. Reference: Baumgardner, D., et al. ~Interpretation of Measurements made by the FSSP-300 during the Airborne Arctic Stratosphenc Expedition." J. Geophys. Res. In press. 1992.


Reactive Nitrogen

Instrument: Reactive Nitrogen

Principal Investigator: David W. Fahey

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.

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Research Scanning Polarimeter

In order to demonstrate the capabilities of polarimetry an instrument that can make either ground-based, or aircraft measurements, the Research Scanning Polarimeter (RSP) has been developed by SpecTIR Corporation. This instrument has similar functional capabilities to the proposed EOSP satellite instrument. The picture above shows the assembled RSP instrument with its liquid nitrogen dewar on the left side and scanner assembly on the right. Currently data acquisition is performed on a laptop, which is shown here and gives an indication of the size of the instrument. The scientific requirements for the polarimetric measurements are satisfied by the RSP through its high measurement accuracy, the wide range of viewing angles measured and by sampling of the spectrum of reflected solar radiation over most of the radiatively significant range. The RSP instrument uses a polarization compensated scan mirror assembly to scan the fields of view of six boresighted, refractive telescopes through ±60° from the normal with respect to the instrument baseplate. The refractive telescopes are paired, with each pair making measurements in three spectral bands. One telescope in each pair makes simultaneous measurements of the linear polarization components of the intensity in orthogonal planes at 0° and 90° to the meridional plane of the instrument, while the other telescope simultaneously measures equivalent intensities in orthogonal planes at 45° and 135°. This approach ensures that the polarization signal is not contaminated by uncorrelated spatial or temporal scene intensity variations during the course of the polarization measurements, which could create false polarization. These measurements in each instantaneous field of view in a scan provide the simultaneous determination of the intensity, and the degree and azimuth of linear polarization in all nine spectral bands.

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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

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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

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