Synonyms: 
DC8
DC-8
NASA DC8
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Cryogenic Hygrometer

Water vapor concentrations are measured using the cryogenically-cooled, chilled mirror hygrometer (Buck Research model CR-1). This instrument has a wide dynamic range (-90 to +30 C or approximately 1 to 30,000 ppmv H2O) and reasonably rapid response time (2 to 20 seconds, depending on the temporal and quantitative characteristics of the change in water vapor concentrations). The model CR-1 hygrometer utilizes a cryogenically chilled mirror and electro-optical technique to determine the dew/frost point of a gas. The primary difference between the CR-1 and other chilled mirror hygrometers is the mechanism used to cool the mirror surface. The mirror surface on which the dew/frost layer is preserved is coupled to a rod cooled by LN2 cryogen. The mirror surface is heated to the dew/frost point by means of a heater winding attached to the mirror rod. A control circuit controlled by optics monitors the reflectance from a LED off the mirror surface and maintains the condensate layer at a preset level. A thermistor embedded in the mirror measures the surface temperature and is output as a direct reading of the dew/frost point of the sample gas.

Air samples for the CR-1 hygrometer are provided by a separate window-mounted droplet-excluding inlet probe which has been used aboard the DC-8 platform in previous field missions. The in situ sampling probe consists of a stainless steel tubing inlet probe insert combined with a Rosemount type102 non-deiced temperature sensor housing. This type forward-facing probe provides inboard sampling of ambient air while maintaining efficient inertial separation of droplets and particles from the sampled air stream. The outer structural portion of the probe is manufactured by Rosemount Aerospace, Inc. and is flight-certified for use aboard both research and commercial jet aircraft. In normal subsonic flight, the inlet is self-pumping and develops enough pressure head to provide up to 15 liters/minute airflow through the approximately the 1 meter of ¼ “ stainless steel tubing which connects the inlet to the sensors. The tubing used to supply the sample air to the hygrometer is heated to approximately 50° C to avoid any chance of internal condensation in the sample line and reduce errors associated with wall effects.

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Video Uplink

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Utah State University Airglow Study

The 1999 Leonid MAC campaign consisted of five consecutive nighttime flights including stops in the United States, England, Israel, and the Azores. The Space Dynamics Laboratory of Utah State University operated several instruments in the visible and infrared spectral bands. One system obtained high-resolution (4 cm-1) measurements of the night sky emission spectra in the 1 to 1.65-micrometer band. Measurements were obtained above the clouds providing exceptional viewing conditions. The OH airglow emission layer originates at an altitude of ~87 km and has a half-width of typically 8–10 km. Its behavior during the storm night of 17/18 November 1999 was of particular interest because the OH airglow emission may be affected by the Leonid meteor ablation products that can penetrate to altitudes as low as 80 to 90 km altitudes. Typical Leonid meteor end-heights are much higher above ~100 km. Variability of the OH emission was measured to investigate any changes that may result from meteor interactions with the atmosphere that could cause changes in the natural airglow emission via excitation caused by the meteor ablation products. It is also possible that organic materials in the meteors could be broken down into simpler products that include the OH hydroxyl radical.

To search for these effects, airglow data were collected by a Bomem Michelson M-150 interferometer. This interferometer operates at 4 cm-1 resolution (apodized) with a scan rate of about 1 scan every 3 seconds. The interferometer field of view is 1.5° and it is sensitive from 1 to 1.65 micrometers. An intensified Xibion camera recorded the instrument field of view during the flight, providing information on the pointing elevation and azimuth. This sensor operated almost continuously during the entire 1999 Leonid MAC campaign and collected an extensive set of night airglow spectra.

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Telescopic High Definition Television

THDTV provides high definition TV imaging with long focal length optics. It consists of a professional Sony HDTV Camcorder studio with a broadcast quality low f-number zoom lens.

This instrument detects wake phenomena at highest possible spatial resolution.

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Frequency Modulated Continuous Wave Snow Thickness Radar

The Center for Remote Sensing of Ice Sheets has developed an ultra-wideband radar that operates over the frequency from 2 to 8 GHz to map near-surface internal layers in polar firn with fine vertical resolution. The radar has also been used to measure thickness of snow over sea ice. Information about snow thickness is essential to estimate sea ice thickness from ice freeboard measurements performed with satellite radar and laser altimeters. This radar has been successfully flown on NASA P-3 and DC-8 aircraft.

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Fibre-optic Fed Slit-Spectrograph

SLIT is a high-resolution slit-spectrgraph which is fed by optical fiber attached to window assembly telescope. Its objective is to resolve shock emissions in the near-UV.

The instrument consists of a computer controlled slit-spectrograph which is fed by an optical fiber and a small telescope assembly at the window. A co-aligned camera provides pointing capability, detecting stars to magnitude +7. The camera is an EM CCD Andor DU97 IN, back illuminated UV enhanced CCD, with 1600x400 pixels (16x16 micron) and 25.6 x 6.4 mm image area. The Spectrometer is an Acton Sp300i imaging spectrometer with 300 mm focal length F/D 4.5. The telescope assembly focussing is performed with a 90 degree off-axis parabolic mirror of 50 mm diameter with a focal length of 100mm. The F/D~2 was chosen to meet the numerical aperture of the fibre optics yielding an angle of view of 0.45 degree. A bundle of 50 quartz fibres of 100 µm diameter are chosen. On the telescope side the fibres form a round cross section of 0.8 mm diameter, on the spectrometer side they are oriented in a row which can be used like a slit with a height of 5.6 mm and a width of 100 micron. If sufficient amounts of light are available, a slit can be used in addition to improve the spectral resolution.

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NOAA Lyman-Alpha Total Water Hygrometer

Total water is measured in situ as vapor with a Lyman-Alpha hygrometer. High ambient sample flows through a closed cell minimize the effect of trapped water. Lyman-a light (121.6 nm) photodissociates water to produce an excited OH radical. The fluorescence from this radical at 309 nm is detected with a phototube and counting system. At aircraft pressures the fluorescence signal is quenched by air which gives a signal that is proportional to mixing ratio. The Lyman-Alpha radiation produced with a DC-discharge lamp is monitored with an iodine ionization cell that is sensitive from 115 nm to 135 nm. Calibration occurs in flight by injecting water vapor directly into the ambient sample flow.

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URI Peroxides and Formaldehyde Instrument

POPS measures CH2O, H2O2, and CH3OOH.

CH2O is measured by aqueous collection followed by enzyme fluorescence detection.

H2O2 and CH3OOH is measured by aqueous collection followed by HPLC separation and enzyme fluorescence detection.

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Sandia National Laboratory 2-channel Radiometer

The Sandia National Laboratory 2-channel radiometer uses two narrow-band (10 nm) filters in the red and near-IR at a sampling rate of many thousands per second. It measures the total radiative output of the SRC during entry in the 380-600 nm band and the 600-900 nm band and detect rapid fluctuations of light output from spacecraft rotation, instabilities in the shock layer, and ablation.

This instrument consists of two photometers, each equipped with a filter of choice: here a low-pass and high-pass cut-off filter. Each photometer measures the sky over a large ~15 degree field of view, at about 5 - 35 degree elevation.

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Particle Into Liquid Sampler

The Particle Into Liquid Sampler (PILS) was developed for rapid automated on-line and continuous measurement of ambient aerosol bulk composition. The general approach is based on earlier devices in which ambient particles are mixed with saturated water vapor to produce droplets easily collected by inertial techniques. The resulting liquid stream is analyzed with an ion chromatograph to quantitatively measure the bulk aerosol ionic components. In this instrument, a modified version of a particle size magnifier is employed to activate and grow particles comprising the fine aerosol mass. A single jet inertial impactor is used to collect the droplets onto a vertical glass plate that is continually washed with a constant water diluent flow of nominally 0.10 ml min-1. The flow is divided and then analyzed by a dual channel ion chromatograph. In its current form, 4.3 min integrated samples were measured every 7 min. The instrument provides bulk composition measurements with a detection limit of approximately 0.1 µg m-3 for chloride, nitrate, sulfate, sodium, ammonium, calcium, and potassium.

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Na, NH4, K, Mg, Ca+2, Cl, NO2, NO3, SO4, PO4, Br-, WSOC
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