DC-8 - AFRC

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.

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.

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.

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.

NIRSPEC detects shock emissions in the range 0.96 - 1.67 micron and measures blackbody continuum in the near-Infrared where the blackbody continuum peaks at lower temperatures.

The instrument consists of an InGaAs camera with a 600 l/mm objective grating. The InGaAs camera detects stars of about J-magnitude +2, meteors of about magnitude -1. The co-aligned intensified camera detects stars of magnitude +6.

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.

NO is measured using a chemiluminescence detector. One of the four NO detectors is used for the NO measurements. NOy is measured simultaneously by catalytically converting it to NO on the surface of gold tubes heated to ±° C, with carbon monoxide (CO) acting as a reducing agent. The converter system is contained in a pod mounted outside the cabin to minimize the length of the inlet tubes. Gas phase-NOy measurements are made by sampling air through the rearward facing inlet which discriminates against particles of diameter larger than 1 mm. The mixing ratios of total NOy (gas phase-NOy + amplified particulate-NOy) are measured by sampling air through the forward facing inlet which is heated to 100° C. The mixing ratios of gas phase and total NOy are measured independently. A humidifier maintains the H2O mixing ratio in sample flows at a few % in order to stabilize the instrument background against humidity variations in the ambient air. The absolute sensitivities of the NO and NOy channels are measured every 80 minutes by adding NO or NO2 standard gases. The pressure in the gold catalytic converter for gas-phase NOy is maintained at a constant value of about 50 hPa, independent of the ambient pressure. The pressure is held constant by controlling the sample flow using a servo-controlled Teflon valve mounted upstream of the converter tube. All parts of the inlet system upstream of the gold catalyst are made of Perfluoroalkoxy (PFA) Teflon which is temperature controlled at 40˚C. The NO2 conversion efficiency is 99.0611%. The HCN conversion efficiency is lower than 5% for dry air with O3 mixing ratios lower than 100 ppbv. It decreases to 2% for humid air with an H2O mixing ratio of 0.1% and O3 mixing ratios lower than 100 ppbv. This instrument is also equipped with an NO2 photolytic converter combined with an NO detector in our first attempt to access the accuracy of the NO2 measurements.

The miniature Echelle spectrograph provides gigh-resolution Echelle spectroscopy, whereby the spectral range (360 - 900 nm) is folded into shorter segments and projected on a CCD camera for simultaneous exposure.

This instrument consists of a 100 mm f4.5 UV Nikkor lens and Catalina Scientific Corp. "Echellette" Spectrograph with Visible Module or UV Module coupled to a Q-Imaging "Intensified Retiga" blue-enhanced image intensified CCD camera.

Scientific objective: Spectral resolution of shock layer radiation. Resolve spectral lines of air plasma emissions at optical wavelengths for the measurement of excitation temperatures. Provide highest possible spectral resolution.

The X-band LRR, which is suitable for aircraft or space-based platforms, enables markedly improved measurement of precipitation drop size and distribution (at 10.7 GHz), as well as rain rate and surface wind speeds, when used in conjunction with other instruments, such as the PR-2. With a receiver less than 1/8th the size and using 50% less power than predecessors, the LRR could lead to a space-borne 25 channel synthetic aperture radiometer that would not be strictly limited by size and power requirements.

The core technology of the LRR – a synthetically thinned aperture radiometer (STAR) – demonstrated the feasibility of a one-dimensional geometric interferometer (no moving parts) for future NASA X-band missions. The lack of a mechanical scanning apparatus found on traditional radiometers makes the LRR payload smaller, lighter, and cheaper to launch while also reducing the complexity and risk of the instrument. The team also conducted an antenna design study that validated the STAR technology in the critical Ku- and Ka-bands.