Synonyms: 
DC8
DC-8
NASA DC8
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Airborne Multichannel Microwave Radiometer

The Airborne Multichannel Microwave Radiometer (AMMR) measures thermal microwave emission (in degrees Kelvin of brightness temperature) from surface and atmosphere. The up-looking radiometer at 21 and 37 GHz is a component of AMMR that was developed in the 1970's for precipitation measurements from an aircraft. The entire AMMR assembly covers a frequency range of 10-92 GHz. The 21/37 GHz unit has been flown in many types of aircraft during the past three decades in various field campaigns. It was refurbished during the year 2000 and is ready for flight again.

The fixed-beam Dicke radiometer has a beam width of about 6 degrees and is currently programmed with radiometric output every second. The temperature sensitivity is < 0.5 K, and the calibration accuracy is about ±4 K. The calibration is performed on the ground by viewing targets of known brightness (e.g., sky and absorber with known brightness temperature). The unit can be installed in one of the windows of the NASA P-3 aircraft so that it views at an angle of about 15º from zenith. Thus, it is necessary to spiral the aircraft gradually down to region below the freezing level in order to make measurements effectively. Ideally, the aircraft descends at the rate of about 1 km per 5 minutes. The system requires a bottle of N2 gas to keep the wave guides dry during the in-flight operation.

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Convair 580 NRC, DC-8 - AFRC, P-3 Orion - WFF
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Advanced Microwave Precipitation Radiometer

The AMPR is a total power passive microwave radiometer producing calibrated brightness temperatures (TB) at 10.7, 19.35, 37.1, and 85.5 GHz. These frequencies are sensitive to the emission and scattering of precipitation-size ice, liquid water, and water vapor. The AMPR performs a 90º cross-track data scan perpendicular to the direction of aircraft motion. It processes a linear polarization feed with full vertical polarization at -45º and full horizontal polarization at +45º, with the polarization across the scan mixed as a function of sin2, giving an equal V-H mixture at 0º (aircraft nadir). A full calibration is made every fifth scan using hot and cold blackbodies. From a typical ER-2 flight altitude of ~20 km, surface footprint sizes range from 640 m (85.5 GHz) to 2.8 km (10.7 GHz). All four channels share a common measurement grid with collocated footprint centers, resulting in over-sampling of the low frequency channels with respect to 85.5 GHz.

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Broadband CO2 Lidar - 1.5 micron version

The Broadband CO2 lidar instrument operates on the principle of differential absorption. This means that the instrument examines the transmission of light through the atmosphere at two or more different wavelengths that are absorbed differently by the species one wishes to measure. There are then two principal elements involved in the measurement—the source and the detector. Passive systems use natural processes such as sunlight or atmospheric emission to generate a number of different wavelengths which are separated for analysis by the detector. Most laser based systems (eg. DIAL lidars) use two or more different laser sources to provide different wavelengths. These systems then might use the same detector for the multiple wavelengths using time separation or modulation to differentiate the signals coming from the different lasers.

This system, however, uses as a detector that can differentiate wavelengths just as conventional passive sensors. The detector was originally developed as the Fabry-Perot passive sensor measuring CO2 using reflected sunlight. Our new approach is made possible by the emergence of a new type of source—the superluminescent light emitting diode (SLED). The SLED has the same high brightness and collimation characteristics as a conventional laser but it emits light over a broader range of wavelengths than conventional lasers. This permits a differential absorption measurement employing a single source with wavelength differentiation in the detector.

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Berkeley Nitrogen Oxides Detector

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Airborne Tropospheric Hydrogen Oxides Sensor

ATHOS uses laser-induced fluorescence (LIF) to measure OH and HO2 simultaneously. OH is both excited and detected with the A2Σ+ (v’=0) → X2π (v”=0) transition near 308 nm. HO2 is reacted with reagent NO to form OH and is then detected with LIF. The laser is tuned on and off the OH wavelength to determine the fluorescence and background signals. ATHOS can detect OH and HO2 in clear air and light clouds from Earth's surface to the lower stratosphere. The ambient air is slowed from the aircraft speed of 240 m/s to 8-40 m/s in an aerodynamic nacelle. It is then pulled by a vacuum pump through a small inlet, up a sampling tube, and into two low-pressure detection cells - the first for OH and the second for HO2. Detection occurs in each cell at the intersection of the airflow, the laser beam, and the detector field-of-view.

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Airborne Raman Ozone, Temperature, and Aerosol Lidar

This is a stratospheric lidar which is configured to fly on the NASA DC-8. It is a zenith viewing instrument, which makes vertical profile measurements of ozone, aerosols and temperature. Stratospheric ozone can be measured at solar zenith angles greater than ~30 degrees, while temperature and aerosols require SZA > 90 degrees. The SNR is maximized under dark coonditions. The measurement of Near-field water vapor measurements is being investigated and could be readily implemented. The instrument utilizes a XeCl excimer laser and a Nd-YAG laser to make DIAL, Raman DIAL, and backscatter measurements. A zenith viewing 16" telescope receives the lidar returns.

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Autonomous Modular Sensor

The Autonomous Modular Sensor (AMS) is an airborne scanning spectrometer that acquires high spatial resolution imagery of the Earth's features from its vantage point on-board low and medium altitude research aircraft. Data acquired by AMS is helping to define, develop, and test algorithms for use in a variety of scientific programs that emphasize the use of remotely sensed data to monitor variation in environmental conditions, assess global change, and respond to natural disasters.

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Airborne Synthetic Aperture Radar

The Airborne Synthetic Aperture Radar (AIRSAR) was an all-weather imaging tool able to penetrate through clouds and collect data at night. The longer wavelengths could also penetrate into the forest canopy and in extremely dry areas, through thin sand cover and dry snow pack. AIRSAR was designed and built by the Jet Propulsion Laboratory (JPL) which also manages the AIRSAR project. AIRSAR served as a NASA radar technology testbed for demonstrating new radar technology and acquiring data for the development of radar processing techniques and applications. As part of NASA’s Earth Science Enterprise, AIRSAR first flew in 1988, and flew its last mission in 2004.

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Airborne Cloud Radar

The utility of millimeter-wave radars have been successfully used for cloud sensing and cloud microphysical studies. Studies of the impact of cloud feedbacks on the earth's radiation budget have underscored the importance of having a means of measuring the vertical distribution of clouds. Millimeter-wave radars can provide this information under most conditions, with high resolution, using a relatively compact system.

The Airborne Cloud Radar (ACR) for profiling cloud vertical structure was developed by the Jet Propulsion Laboratory and the University of Massachusetts in 1996. It is a W-band (95 GHz) polarimetric Doppler radar designed as a prototype airborne facility for the development of the 94 GHz Cloud Profiling Radar (CPR) for NASA CloudSat mission.

The ACR is a third-generation millimeter-wave cloud radar. While adopting the well tested techniques used by its predecessors, ACR also has a number of new features including an internal calibration loop, frequency agility, digital I and Q demodulation, digital matched filtering, and a W-band low-noise amplifier.

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DC-8 - AFRC, P-3 Orion - WFF, Twin Otter (DOE)
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