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.

The NOy instrument has three independent chemiluminescence detectors for simultaneous measurements of NOy, NO2, and NO. Each detector utilizes the reaction between NO in the sample with reagent O3. The NO/O3 reaction produces excited state NO2 which emits light of near 1µ m wavelength. Emitted photons are detected with a cooled photomultiplier tube.

Because NOy species other than NO do not respond in the chemiluminescence detector, NOy component species are reduced to NO by catalytic reduction on a gold surface with carbon monoxide (CO) acting as a reducing agent. Conversion efficiencies are > 90% at surface temperatures of 300°C. An NO signal representing NOy is then detected by chemiluminescence in the detector module. The catalyst is located outside the aircraft fuselage in order to avoid inlet line losses. NO2 is photolytically converted to NO in a glass cell in the presence of intense UV light between 300 and 400 nm. The conversion fraction is > 50% for a residence time of 1 s. The chemiluminescence detector detects NO as well as the additional NO from NO2. The third channel measures NO directly by passing the ambient sample through the detector module.

The response of each detector is checked several times in flight by standard addition of NO or NO2 calibration gas. The baseline of each measurement is determined in part by the addition of synthetic air that contains no reactive nitrogen. A continuous flow of water vapor is added directly to the sample flow in order to reduce the background signal in the detectors.

The sampling inlet for NOy is located outside the fuselage of the aircraft in a separate football-shaped housing. The shape of the housing allows for the inertial separation of large aerosols (> 5 µm diameter) from the NOy inlet at the downstream end of the housing.

The RC-30 is an airborne film camera system, using color infrared, natural color and black and white film, to obtain high resolution earth imagery.

The Itek Iris II Panoramic Camera has been employed to acquire high resolution land use and land cover data. The Forest Service has used this camera extensively for assessing timber resources and monitoring gypsy moth defoliation in the Appalachian hardwood forests. The Iris II provides a 4.5 x 34.7 inch (11.4 x 88.1 cm) image covering 2.0 x 21.4 miles (3.2 x 34.2 km) on the ground. The high resolution twenty-four inch lens provides a scale at nadir on the panoramic image of half-mile to the inch. With its 10,000 foot film capacity the Iris II allows extended flight duration allowing photography acquisition over very large areas.

Hycon HR-732 cameras are used to acquire high resolution photography in a 9 x 18 inch format. These cameras can be flown in pairs or one camera may be paired with an RC-10 mapping camera. The HR-732s acquire high resolution photography with twenty-four inch focal length lenses providing an image scale of half-mile to the inch. The large scale high resolution photography provided by these cameras is used by agencies such as the Forest Service for timber resource management and by the Fish and Wildlife Service for wetlands inventories and wildlife habitat mapping.

The NO2-ClO-ClONO2-BrO instrument is composed of two separate instruments: A laser-induced fluorescence instrument for the detection of NO2 and a thermal dissociation/resonance fluorescence instrument for the detection of ClO, ClONO2 and BrO.

The NO2 detection system uses laser-induced resonance fluorescence (LIF) for the direct detection of NO2. Ambient air passes through a detection axis where the output of a narrow bandwidth (0.06 cm-1), tunable dye laser operating near 585 nm is used to excite a rovibronic transition in NO2. The excited NO2 molecules are either quenched by collision with air or fluorescence. The NO2 fluorescence is strongly red-shifted, with emission occurring over a broad range of wavelengths from 585 nm to the mid-infrared. The specificity of the technique is accomplished by tuning the laser frequency on and off resonance with a narrow spectral feature (0.04 cm-1) in the NO2 absorption spectrum. The difference between the fluorescence signal on and off resonance is related to the mixing ratio of NO2 through laboratory and in-flight calibrations. The observations are determined with an accuracy (1 sigma) of ±10% ±50 pptv, precision (1 sigma) of ±40 pptv, and a reporting interval of 10 seconds. Higher resolution (0.25 sec) data available on request.

The halogen detection system uses gas-phase thermal dissociation of ambient ClONO2 to produce ClO and NO2 radicals. The pyrolysis is accomplished by passing the air sampled in a 5-cm-square duct through a grid of resistively heated silicon strips at 10 to 20 m/sec, rapidly heating the air to 520 K. The ClO fragment from ClONO2 is converted to Cl atoms by reaction with added NO, and Cl atoms are detected using ultra-violet resonance fluorescence at 118.9 nm. A similar detection axis upstream of the heater provides simultaneous detection of ambient ClO. An identical twin sampling duct provides the capability for diagnostic checks. The flight instrument is calibrated in a laboratory setting with known addition of ClONO2 as a function of pressure, heater temperature and flow velocity. The concentration of ClONO2 is measured with an accuracy and detection limit of ±20% and 10 pptv, respectively, in 35 seconds (all error estimates are 1 sigma). The concentration of ClO is measured with an accuracy and detection limit of ±17% and 3 pptv, respectively, in 35 seconds.

Measures the vertical profile of atmospheric temperature, pressure, relative humidity, and wind speed and direction as the sonde falls from altitude to ocean surface.

The FSSP is of that general class of instruments called optical particle counters (OPCs) that detect single particles and size them by measuring the intensity of light that the particle scatters when passing through a light beam. A Helium Neon laser beam is focused to a diameter of 0.2 mm at the center of an inlet that faces into the oncoming airstream. This laser beam is blocked on the opposite side of the inlet with an optical stop, a "dump spot" to prevent the beam from entering the collection optics. Particles that encounter this beam scatter light in all directions and some of that scattered in the forward direction is directed by a right angle prism though a condensing lens and onto a beam splitter. The "dump spot" on the prism and aperture of the condensing lens define a collection angle from about 4º - 12º.

The beam splitter divides the scattered light into two components, each of which impinge on a photodetector. One of these detectors, however, is optically masked to receive only scattered light when the particles pass through the laser beam displaced greater than approximately 1.5 mm either side of the center of focus. Particles that fall in that region are rejected when the signal from the masked detector exceeds that from the unmasked detector. This defines the sample volume needed to calculate particle concentrations.

In early 2000, the Ames Atmospheric Radiation Group completed the design and development of an all new Solar Spectral Flux Radiometer (SSFR). The SSFR is used to measure solar spectral irradiance at moderate resolution to determine the radiative effect of clouds, aerosols, and gases on climate, and also to infer the physical properties of aerosols and clouds. Additionally, the SSFR was used to acquire water vapor spectra using the Ames 25-meter base-path multiple-reflection absorption cell in a laboratory experiment. The Solar Spectral Flux Radiometer is a moderate resolution flux (irradiance) spectrometer with 8-12 nm spectral resolution, simultaneous zenith and nadir viewing. It has a radiometric accuracy of 3% and a precision of 0.5%. The instrument is calibrated before and after every experiment, using a NIST-traceable lamp. During field experiments, the stability of the calibration is monitored before and after each flight using portable field calibrators. Each SSFR consists of 2 light collectors, which are either fix-mounted to the aircraft fuselage, or on a stabilizing platform which counteracts the movements of the aircraft. Through fiber optic cables, the light collectors are connected to 2 identical pairs of spectrometers, which cover the wavelength range from (a) 350 nm-1000 nm (Zeiss grating spectrometer with Silicon linear diode array) and (b) 950 nm - 2150 nm (Zeiss grating spectrometer with InGaAs linear diode array). Each spectrometer pair covers about 95% of the incoming solar incident irradiance spectrum.