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At least 775 records · Page 43
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Analysis of wind profile measurements from an instrumented aircraft

The results of an experimental program to determine the capability of measuring wind profiles on support of STS operations with an instrumented aircraft are discussed. These results are a compilation of the flight experiments and the statistical data comparing the quality of the aircraft measurements with quasi-simultaneous and quasi-spatial overlapping Jimsphere measurements. An instrumented aircraft was chosen as a potential alternative to the Jimsphere/radar system for expediting the wind profile calculation by virtue of the ability of an aircraft to traverse the altitudes of interest in roughly 10 minutes. The two aircraft which participated in the study were F-104 and ER-2.

Paige, Terry S.↗
NASA NTRS1990

High altitude reconnaissance aircraft

At the equator the ozone layer ranges from 65,000 to 130,000 plus feet, which is beyond the capabilities of the ER-2, NASA's current high altitude reconnaissance aircraft. The Universities Space Research Association, in cooperation with NASA, is sponsoring an undergraduate program which is geared to designing an aircraft that can study the ozone layer at the equator. This aircraft must be able to cruise at 130,000 feet for six hours at Mach 0.7, while carrying 3,000 lbs. of payload. In addition, the aircraft must have a minimum range of 6,000 miles. In consideration of the novel nature of this project, the pilot must be able to take control in the event of unforeseen difficulties. Three aircraft configurations were determined to be the most suitable - a joined-wing, a biplane, and a twin-boom conventional airplane. The performance of each configuration was analyzed to investigate the feasibility of the project.

Yazdo, Renee Anna↗
NASA NTRS1990

The NASA-ER2 meteorological measurement system: Instrumentaion, calibration and intercomparison results

The NASA ER-2 aircraft is used as a platform for high altitude atmospheric missions. The Meteorological Measurement System (MMS) was designed specifically for atmospheric research to provide accurate, fast response, in situ measurements of pressure, temperature, and the three dimensional wind vector. The MMS consists of three subsystems: an air motion sensing system to measure the velocity of the air with respect to the aircraft, a high resolution Inertial Navigation System (INS) to measure the velocity of the aircraft with respect to the Earth, and a Data Acquisition System, to sample, process and record the measured quantities. Details of each of these systems are given. The location of the MMS instrumentation is illustrated. The calibration of the MMS is discussed and results on an intercomparison of MMS measurements, Vaisala radiosonde observation and radar tracking data are given. An illustration of the MMS measurement of vertical wind is given.

Chan, K. Roland↗
NASA NTRS1983

Science program for an imaging radar receiving station in Alaska. Report of the science working group

It is argued that there would be broad scientific benefit in establishing in Alaska an imaging radar receiving station that would collect data from the European Space Agency's Remote Sensing Satellite, ERS-1. This station would acquire imagery of the ice cover from the American territorial waters of the Beaufort, Chukchi, and Bering Seas. This station, in conjunction with similar stations proposed for Kiruna, Sweden, and Prince Albert, Canada would provide synoptic coverage of nearly the entire Arctic. The value of such coverage to aspects of oceanography, geology, glaciology, and botany is considered.

Source record↗
NASA NTRS1991

NASA/Ames Research Center's science and applications aircraft program

NASA-Ames Research Center operates a fleet of seven Science and Applications Aircraft, namely the C-141/Kuiper Airborne Observatory (KAO), DC-8, C-130, Lear Jet, and three ER-2s. These aircraft are used to satisfy two major objectives, each of equal importance. The first is to acquire remote and in-situ scientific data in astronomy, astrophysics, earth sciences, ocean processes, atmospheric physics, meteorology, materials processing and life sciences. The second major objective is to expedite the development of sensors and their attendant algorithms for ultimate use in space and to simulate from an aircraft, the data to be acquired from spaceborne sensors. NASA-Ames Science and Applications Aircraft are recognized as national and international facilities. They have performed and will continue to perform, operational missions from bases in the United States and worldwide. Historically, twice as many investigators have requested flight time than could be accommodated. This situation remains true today and is expected to increase in the years ahead. A major advantage of the existing fleet of aircraft is their ability to cover a large expanse of the earth's ecosystem from the surface to the lower stratosphere over large distances and time aloft. Their large payload capability allows a number of scientists to use multi-investigator sensor suites to permit simultaneous and complementary data gathering. In-flight changes to the sensors or data systems have greatly reduced the time required to optimize the development of new instruments. It is doubtful that spaceborne systems will ever totally replace the need for airborne science aircraft. The operations philosophy and capabilities exist at NASA-Ames Research Center.

Hall, G. Warren↗
NASA NTRS1991

Hyperspectral data analysis for estimation of foliar biochemical content along the Oregon transect

The NASA Oregon Transect Ecosystem Research (OTTER) project completed a data acquisition phase. Data were acquired with several airborne imaging spectrometers. Included were the Airborne Visible and Infrared Imaging Spectrometer (AVIRIS) aboard the ER-2, the Advanced Solidstate Array Spectrometer (ASAS) aboard the C-130, and the Fluorescence Line Imager (FLI) and Compact Airborne Spectrographic Imager (CASI), both aboard light aircraft. In addition, Spectron visible and near-infrared data were acquired in transects across study areas from a low-altitude ultralight craft. Sunphotometer data were taken approximately coincident with each overflight for atmospheric correction of the aircraft data.

Johnson, Lee F.↗
NASA NTRS1991

The high altitude aircraft program of NASA/Ames Research Center

The ER-2 aircraft are used in NASA's Airborne Science and Applications Program as readily deployable high altitude sensor platforms to collect remote sensing and in situ data on Earth resources, celestial phenomena, atmospheric dynamics, and oceanic processes. Additionally, these aircraft are used for electronic sensor research and development and satellite investigative support. The scientific endeavors supported by these aircraft are listed.

Shelton, Gary↗
NASA NTRS1990

New laser materials for laser diode pumping

The potential advantages of laser diode pumped solid state lasers are many with high overall efficiency being the most important. In order to realize these advantages, the solid state laser material needs to be optimized for diode laser pumping and for the particular application. In the case of the Nd laser, materials with a longer upper level radiative lifetime are desirable. This is because the laser diode is fundamentally a cw source, and to obtain high energy storage, a long integration time is necessary. Fluoride crystals are investigated as host materials for the Nd laser and also for IR laser transitions in other rare earths, such as the 2 micron Ho laser and the 3 micron Er laser. The approach is to investigate both known crystals, such as BaY2F8, as well as new crystals such as NaYF8. Emphasis is on the growth and spectroscopy of BaY2F8. These two efforts are parallel efforts. The growth effort is aimed at establishing conditions for obtaining large, high quality boules for laser samples. This requires numerous experimental growth runs; however, from these runs, samples suitable for spectroscopy become available.

Jenssen, H. P.↗
NASA NTRS1990

Altimeter crossover methods for precision orbit determination and the mapping of geophysical parameters

Accurate orbit determination and the recovery of geophysical parameters are presently attempted via methodologies which use differenced height measurements at the points where the ground tracks of the altimetric satellite orbits intersect. Such 'crossover measurements' could significantly improve the earth's gravity field model. Attention is given to a novel technique employing crossover measurements from two satellites carrying altimeter instruments; this method can observe zonal harmonics of the earth's geopotential which are weakly observed through single-satellite crossovers. This dual-satellite crossover technique will be applicable to data from such future oceanographic satellites as ERS-1.

Shum, C. K.↗
NASA NTRS1990

Interpretation of aircraft measurements of NO, ClO, and O3 in the lower stratosphere

Results are presented from an October 17, 1988, flight of the NASA ER-2 stratospheric research aircraft. The flight sampled a nearly constant air mass at 20 km altitude, near 39 deg N latitude, from before sunrise until near noon. The instrumentation on board simultaneously measured NO, ClO, O3, temperature, and pressure. The measurements are combined with modeled photodissociation coefficients and known reaction kinetics to infer abundances of other important species, and the results are compared to previous estimates as a test for consistency in the understanding of the photochemical processes governing the species distributions.

Kawa, S. R.↗
NASA NTRS1990

Remote sensing contribution to land surface hydrology

Progress that has been made over the past decade in developing technology for hydrological observations from operational aircraft is described. Particular attention is given to research on soil moisture, snow cover, and vegetation. Future missions such as the ESA ERS-1 and Canada's Radarsat mission are considered.

Salomonson, V. V.↗
NASA NTRS1989

Ice classification algorithm development and verification for the Alaska SAR Facility using aircraft imagery

The Alaska SAR Facility (ASF) at the University of Alaska, Fairbanks is a NASA program designed to receive, process, and archive SAR data from ERS-1 and to support investigations that will use this regional data. As part of ASF, specialized subsystems and algorithms to produce certain geophysical products from the SAR data are under development. Of particular interest are ice motion, ice classification, and ice concentration. This work focuses on the algorithm under development for ice classification, and the verification of the algorithm using C-band aircraft SAR imagery recently acquired over the Alaskan arctic.

Holt, Benjamin↗
NASA NTRS1990

Cirrus structure and radiative parameters from airborne lidar and spectral radiometer observations - The 28 October 1986 FIRE study

A description is presented of cirrus based on results from a FIRE observation flight in central Wisconsin on October 28, 1986. Cirrus structure and radiative parameters as determined by the ER-2 lidar and imaging spectral radiometers are presented. From the lidar observations a complex structure was shown with differing cloud layers extending over six kilometers of altitude range. Both thin and dense cirrus layers were present and mixed phase clouds were found at lower altitudes. As indicated by the cloud structure, precipitation of crystals from high, but vertically thin, layers produces a significant fraction of the lower cirrus. Multiple layers should be considered as normal for cirrus formations. It is noted that the cloud height is an important factor for satellite cloud retrievals and cloud climatology.

Spinhirne, James D.↗
NASA NTRS1990

The 27-28 October 1986 FIRE IFO cirrus case study - Comparison of radiative transfer theory with observations by satellite and aircraft

Observations of cirrus and altocumulus clouds during the FIRE are compared to theoretical models of cloud radiative properties. Three tests are performed. First, radiances are used to compare the relationship between nadir reflectance ot 0.83 micron and beam emittance at 11.5 microns with that predicted for model calculations using spherical and nonspherical phase functions. Good agreement is found between observations and theory when water droplets dominate. Poor agreement is found when ice particles dominate, especially using spherical-particle phase functions (SPPFs). Even when compared to a laboratory-measured ice-particle phase function (IPPF), the observations show great side-scattered radiation than the theoretical calculations. Second, the anisotropy of conservatively scattered radiation is examined using simultaneous multiple angle views of the cirrus from Landsat and ER-2 aircraft radiometers. Observed anisotropy gives good agreement with theoretical calculations using the laboratory IPPF and poor agreement with an SPPF. Third, Landsat radiances at 0.83, 1.65, and 2.21 microns are used to infer particle phase and size. For water droplets, good agreement is found with particle-probe measurements in the cloud. For ice particles, the Landsat radiance observations predict an effective radius of 60 microns versus aircraft observations of about 200 microns. It is suggested that this discrepancy may be explained by uncertainty in the imaginary index of ice and by inadequate measurements of small ice particles by microphysical probes.

Wielicki, Bruce A.↗
NASA NTRS1991

In situ measurements of midlatitude ClO in winter

In situ measurements of ClO in the winter lower stratosphere are presented for six flights of the NASA ER-2 aircraft from 38 deg N to 61 deg N. Enhanced abundances, increasing in severity with date, were observed below 20 km, where HCl and ClONO2 dominate the inorganic chlorine budget. The greatest mixing ratios, over 150 pptv, were encountered on February 20 and 21, 1989, as the vortex experienced a major warming. Although the timing of these ClO enhancements and the evidence that vortex air can reach midlatitudes suggest that heterogeneous conversion of chlorine compounds within the vortex influences chemistry at midlatitudes, the enhacements observed early in the winter could have been caused by unknown chemistry occurring outside the vortex. In either case, photochemical loss of ozone due to catalytic reactions involving ClO at these mixing ratios may be responsible in part for the ozone decreases observed at high latitudes in the Northern Hemisphere.

Toohey, D. W.↗
NASA NTRS1991

The influence of polar heterogeneous processes on reactive chlorine at middle latitudes - Three dimensional model implications

Three-dimensional model calculations with the NASA/GSFC chemistry and transport model have been designed to consider the impact of heterogeneous processes occurring on polar stratospheric clouds (PSCs) in the Arctic vortex on the HCl distribution. By examining the HCl concentration for a calculation with PSCs relative to a calculation with gas phase chemistry only, the impact of polar processing on reactive chlorine species at middle latitudes is inferred. Results from the chemistry and transport model reproduce basic features of the ClO measurements (Toohey et al., 1991), which were made on the ferry flights of the ER-2 from Stavanger, Norway to Moffett Field, California via Wallops Island, Virginia on February 20 and 21, 1989. The model indicates that perturbed air which is contained within the polar vortex during winter is not homogeneously mixed, and that the ferry flights were made through air with the largest conversion of HCl to reactive chlorine that is seen at middle latitudes.

Douglass, Anne R.↗
NASA NTRS1991

Determination of the optical thickness and effective particle radius of clouds from reflected solar radiation measurements. II - Marine stratocumulus observations

A multispectral scanning radiometer has been used to obtain measurements of the reflection function of marine stratocumulus clouds at 0.75 micron and at 1.65 and 2.16 microns. These observations were obtained from the NASA ER-2 aircraft as part of the FIRE, conducted off the coast of southern California during July 1987. Multispectral images of the reflection function were used to derive the optical thickness and the effective particle radius of stratiform cloud layers on four days. In addition to the radiation measurements, in situ microphysical measurements were obtained from an aircraft. In this paper, the remote sensing results are compared with in situ observations, which show a good spatial correlation for both optical thickness and effective radius. These comparisons further show systematic differences between remote sensing and in situ values, with a tendency for remote sensing to overestimate the effective radius by about 2-3 microns, independent of particle radius. The optical thickness, in contrast, is somewhat overestimated for small optical thicknesses and underestimated for large optical thicknesses. An introduction of enhanced gaseous absorption at a wavelength of 2.16 microns successfully explains some of these observed discrepancies.

Nakajima, Teruyuki↗
NASA NTRS1991

Room temperature Dy:YLF laser operation at 4.34 micron

A Dy:YLF laser operating on the 6H11/2 to 6H13/2 transition at 4.34 micron and using a laser pumping scheme is reported. This pumping scheme is necessitated by the short upper-laser-level lifetime and the small effective stimulated-emission cross section. A suitable laser for this application is the Er:YLF laser operating at 1.73 micron. A simple model that approximates Dy:YLF laser performance well is presented. Results on laser performance, including a determination of the slope efficiency and threshold as a function of the output mirror reflectivity and a correlation of the pulse length with the laser output energy, are reported. Overall laser efficiency is found to be limited primarily by the ratio of the pump wavelength to laser output wavelength and the terminated four-level laser operation. Spectroscopic results, including the measurement of the absorption spectra and the lifetimes of both the upper- and lower-laser manifolds, are given.

Barnes, Norman P.↗