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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS2006

Real Time Mars Approach Navigation Aided by the Mars Network

A NASA Mars technology project is described that is building a prototype embedded real time Mars approach navigation capability which can be hosted on the Mars Network's Electra transceiver. The paper motivates the reason for doing real time Mars approach navigation via a set of analyses demonstrating its utility for enabling Mars pin-point landing (less than 1-km landing error). The development approach, software design, and test results are discussed. Finally, the way forward towards a flight demonstration on the Mars Science Laboratory (MSL) is presented.

Mars Network↗
NASA NTRS1979

Airborne laser induced fluorescence system for measuring OH and other trace gases in the parts-per-quadrillion to parts-per-trillion range

Described in detail is a laser induced fluorescence system which has been successfully interfaced with two aircraft sampling platforms (i.e., Sabreliner jet and an L-188C Electra). This system, which has been under development for four years, presently consists of the following major components: (1) a Nd-Yag laser driven oscillator-amplifier dye laser; (2) a sampling manifold with associated fluorescence detection optics; (3) an OH calibration chamber; (4) a laser beam steering assembly; and (5) sampling electronics and data processing hardware. During the last three years, this system has been flown some 50,000 air miles making tropospheric OH radical measurements over the latitude range of 70 N to 57 S. OH concentrations measured during these flights have ranged from 30 parts-per-quadrillion (3.7 x 10 to the 5th molecules/sq cm) at altitudes of 6 km to 0.8 parts-per-trillion (2.0 x 10 to the 7th molecules/sq cm) at 0.5 km. Computations have been completed which indicate that the existing aircraft system with modest modifications should also be capable of detecting natural tropospheric levels of NO, SO2, CH2O, NO2, HNO2, NO3, H2O2 and CS2 by using both conventional laser-induced fluorescence methodology and multiphoton techniques.

Davis, D. D.↗
NASA NTRS1982

IUE observations of reflection nebulae

Low-resolution IUE spectra in the SWP and LWR ranges were obtained of several reflection nebulae in the vicinity of their respective illuminating stars. Data for NGC 7023 (HD200775), NGC 1435 (Merope, 23 Tau), NGC 1432 (Maia, 20 Tau) and the Electra (17 Tau) nebula were found to display significant differences in the shape of their normalized nebular spectra. If the dust in these nebulae is similar from one object to the next, these differences can be most readily explained by differences in the line-of-sight dust distribution, coupled with a wavelength-dependent phase function, changing from a strongly forward throwing form (g = 0.6-0.7) in the visible to a more nearly isotropic shape (g approximately 0.25) at 1400A.

Witt, A. N.↗
NASA NTRS1982

CO, O3, and aerosol measurements from NASA Global Tropospheric Experiment - Test flights 1981

A series of four instrument test flights was conducted during July 1981 in preparation for the NASA Global Tropospheric Experiment. The purpose of the flights was to demonstrate the feasibility and value of simultaneously measuring several specific atmospheric pollutants over a 25 deg latitudinal range. Carbon monoxide and methane grab samples were obtained simultaneously with nearly continuous in situ ozone and remote ozone and aerosol optical radar measurements. The sampling platform was a NASA Electra, a four engine turboprop aircraft. Attention is given to CO and CH4 sample collection and analysis, ozone measurement methods, the aerosol measurement method, an interpretation of the optical radar display, and a synergistic consideration of results.

Hinton, R. R.↗
NASA NTRS1984

Ocean waves and turbulence as observed with an adaptive coherent multifrequency radar

An adaptive coherent multifrequency radar system is developed for several applications. The velocity distribution (Doppler spectrum) and spectral intensity of 15 different irregularity scales (waves and turbulence) can be measured simultaneously. Changing the azimuth angle of the antennas at regular intervals, the directivity of the wave/turbulence pattern on the sea surface can also be studied. A series of measurements for different air/sea conditions are carried out from a coast based platform. Experiments in the Atlantic are also performed with the same equipment making use of the NASA Electra aircraft. The multifrequency radar allows the measurement of the velocity distribution (""coherent and incoherent component'') associated with 15 different ocean irregularity scales simultaneously in a directional manner. It is possible to study the different air/sea mechanisms in some degree of detail.

Gjessing, D. T.↗
NASA NTRS1985

Airborne DIAL System for Remote Tropospheric Sensing

Spatial distribution of gases and of aerosols measured. Airborne DIAL system uses two frequency-doubled Nd:YAG lasers and mounted in NASA Wallops Electra aircraft. Multipurpose airborne differential absorption lidar (DIAL) system, developed at Langley Research Center, remotely measures profiles of various gases and aerosols in diverse atmospheric investigations. Capability to rapidly determine spatial distribution of gases such as ozone, water vapor, sulfur dioxide, and nitrogen dioxide and to measure simultaneously distribution of aerosols at several laser wavelengths provides opportunity for developing extensive data base for examining complex interaction of atmospheric dynamics and chemistry.

Browell, E. V.↗
NASA NTRS1985

Development and operation of a real-time data acquisition system for the NASA-LaRC differential absorption lidar

Computer hardware and software of the NASA multipurpose differential absorption lidar (DIAL) sysatem were improved. The NASA DIAL system is undergoing development and experimental deployment for remote measurement of atmospheric trace gas concentration from ground and aircraft platforms. A viable DIAL system was developed with the capability of remotely measuring O3 and H2O concentrations from an aircraft platform. Test flights were successfully performed on board the NASA/Goddard Flight Center Electra aircraft from 1980 to 1984. Improvements on the DIAL data acquisition system (DAS) are described.

Butler, C.↗
NASA NTRS1985

Airborne lidar measurements of El Chichon stratospheric aerosols

A NASA Electra airplane, outfitted with a lidar system, was flown in January to February 1983 between the latitudes of 27 deg N and 76 deg N. One of the primary purposes of this mission was to determine the spatial distribution and aerosol characteristics of the El Chichon-produced stratospheric material. This report presents the lidar data from that flight mission. Representative profiles of lidar backscatter ratio, plots of the integrated backscattering function versus latitude, and contours of backscatter mixing ratio versus altitude and latitude are given. It addition, tables containing numerical values of the backscatter ratio and backscattering function versus altitude are supplied for each profile. The largest amount of material produced by the El Chichon eruptions of late March to early April 1982, which was measured by this flight, resided between 35 deg N and 52 deg N. Peak backscatter ratios at a wavelength of 0.6943 micro m decreased from 8 to 10 at the lower latitudes to 3 at the higher latitudes. Backscatter ratio profiles taken while crossing the polar vortex show that the high-altitude material from El Chichon arrived at the north polar region sometime after the winter polar vortex was established. This report presents the results of this mission in a ready-to-use format for atmospheric and climatic studies.

Mccormick, M. P.↗
NASA NTRS1985

Airborne Lidar measurements of aerosols, mixed layer heights, and ozone during the 1980 PEPE/NEROS summer field experiment

A detailed summary of the NASA Ultraviolet Differential Absorption Lidar (UV DIAL) data archive obtained during the EPA Persistent Elevated Pollution Episode/Northeast Regional Oxidant Study (PEPE/NEROS) Summer Field Experiment Program (July through August 1980) is presented. The UV dial data set consists of remote measurements of mixed layer heights, aerosol backscatter cross sections, and sequential ozone profiles taken during 14 long-range flights onboard the NASA Wallops Flight Center Electra aircraft. These data are presented in graphic and tabular form, and they have been submitted to the PEPE/NEROS data archive on digital magnetic tape. The derivation of mixing heights and ozone profiles from UV Dial signals is discussed, and detailed intercomparisons with measurements obtained by in situ sensors are presented.

Browell, E. V.↗
NASA NTRS1986

Theory and operation of the real-time data acquisition system for the NASA-LaRC differential absorption lidar (DIAL)

The improvement of computer hardware and software of the NASA Multipurpose Differential Absorption Lidar (DIAL) system is documented. The NASA DIAL system is undergoing development and experimental deployment at NASA Langley Research Center for the remote measurement of atmospheric trace gas concentrations from ground and aircraft platforms. A viable DIAL system was developed capable of remotely measuring O3 and H2O concentrations from an aircraft platform. Test flights of the DIAL system were successfully performed onboard the NASA Goddard Flight Center Electra aircraft from 1980 to 1985. The DIAL Data Acquisition System has undergone a number of improvements over the past few years. These improvements have now been field tested. The theory behind a real time computer system as it applies to the needs of the DIAL system is discussed. This report is designed to be used as an operational manual for the DIAL DAS.

Butler, C.↗
NASA NTRS1986

Real-time atmospheric absorption spectra for in-flight tuning of an airborne dial system

Real-time measurements of atmospheric absorption spectra are displayed and used to precisely calibrate and fix the frequency of an Alexandrite laser to specific oxygen absorption features for airborne Differential Absorption Lidar (DIAL) measurements of atmospheric pressure and temperature. The DIAL system used contains two narrowband tunable Alexandrite lasers: one is electronically scanned to tune to oxygen absorption features for on-line signals while the second is used to obtain off-line (nonabsorbed) atmospheric return signals. The lidar operator may select the number of shots to be averaged, the altitude, and altitude interval over which the signals are averaged using single key stroke commands. The operator also determines exactly which oxygen absorption lines are scanned by comparing the line spacings and relative strengths with known line parameters, thus calibrating the laser wavelength readout. The system was used successfully to measure the atmospheric pressure profile on the first flights of this lidar, November 20, and December 9, 1985, aboard the NASA Wallops Electra aircraft.

Dombrowski, M.↗
NASA NTRS1987

Airborne lidar measurements of El Chichon stratospheric aerosols, January 1984

A lidar-equipped NASA Electra aircraft was flown in January 1984 between the latitude of 38 and 90 deg N. One of the primary purposes of this mission was to determine the spatial distribution and aerosol characteristics of El Chichon produced stratospheric material. Lidar data from that portion of the flight mission between 38 deg N and 77 deg N is presented. Representative profiles of lidar backscatter ratio, a plot of the integral backscattering function versus latitude, and contours of backscatter mixing ratio versus altitude and latitude are given. In addition, tables containing numerical values of the backscatter ratio and backscattering function versus altitude are applied for each profile. These data clearly show that material produced by the El Chichon eruptions of late March-early April 1982 had spread throughout the latitudes covered by this mission, and that the most massive portion of the material resided north of 55 deg N and was concentrated below 17 km in a layer that peaked at 13 to 15 km. In this latitude region, peak backscatter ratios at a wavelength of 0.6943 microns were approximately 3 and the peak integrated backscattering function was about 15 X 10 to the -4/sr corresponding to a peak optical depth of approximately 0.07. This report presents the results of this mission in a ready-to-use format for atmospheric and climatic studies.

Mccormick, M. Patrick↗
NASA NTRS1987

Parametric representation of heat and moisture fluxes in cloud-topped mixed layers

The Betts (1973, 1978) parametrization of heat and moisture fluxes is tested using measurements made in thin, broken, and solid stratocumulus clouds by the NCAR Electra off the California coast in June 1976. The turbulence data are used to determine updraft-downdraft properties, heat and moisture fluxes, spectra, and cospectra. From the convective properties, vertical mass flux profiles are obtained and examined for consistency. A convective scaling which is appropriate for cloud-topped mixed layers is discussed. The results demonstrate the usefulness of a mass flux formulation in modeling applications for cloud conditions varying between solid and broken.

Penc, Richard S.↗
NASA NTRS1987

In situ ozone instrumentation for 10-Hz measurements - Development and evaluation

The development of the fast-response ozone detector for the Electra aircraft is described. The selection of a technique to meet the design goal of 10-Hz detection is examined in terms of detection principles, instrument sampling parameters, signal conditioning, and aircraft and sampling environment. An instrument which employs a NO technique for detection of ozone with a reaction chamber volume of 16 cu cm, a pressure of 60 torr, and a sample flow of 1000 standard cu cm/min was developed. Laboratory and flight testings of the detector were conducted in order to evaluate its performance. The data reveal that the fast-response ozone detector is highly reliable with a response of 0.1 sec to 90 percent of reading, has a lower detection limit of 1 ppbv, and an S/N of 20 at 20 ppbv ozone.

Gregory, G. L.↗
NASA NTRS1988

Carbon monoxide over the Amazon Basin during the 1985 dry season

During the Amazon Boundary Layer Experiment, approximately 100 hours of in situ carbon monoxide measurements were obtained using a tunable diode laser sensor that provided continuous, fast-response (about 1 s) measurements. This data set, taken on board the NASA Electra between July 12 and August 12, 1985, characterizes the temporal and spatial changes in the CO distribution over the Amazon Basin as meteorological conditions progressed from the early to middle phases of the 1985 day season. Early dry-season CO values of 75-95 ppbv were generally observed in the PBL. As the dry season became well established, biomass burning and a persistent capping inversion at about 3 km profoundly altered the CO distribution, with PBL values typically reaching 150-275 ppbv. Concentrations as high as 800 ppbv were measured within identifiable haze layers. An analysis of satellite imagery shows that biomass burning was occurring along the Amazon River system and in savannah areas located more than 1000 km south of the region sampled.

Sachse, G. W.↗
NASA NTRS1988

Tropospheric ozone and aerosol distributions across the Amazon Basin

As a part of the NASA Global Tropospheric Experiment to study the Amazon boundary layer, ozone and aerosol distributions were made measured in July-August 1985 by a NASA Electra aircraft on several long-range flights spanning different areas between Tabatinga and Belem, Brazil. Both positive and negative correlations were found in PBL between aerosol concentrations and O3 mixing ratios. The negative correlations result from the downward transport of relatively clean O3-rich air from the upper troposphere into PBL (which normally has higher aerosol loading and lower O3 concentrations than troposphere); positive correlations are found in biomass-burning plumes, where the aerosols are emitted into the air and O3 is photochemically produced. It was found that, in the dry season, a significant portion of the ozone over the rain forest is a result of biomass burning and that the distribution of photochemically produced O3 is strongly affected by synoptic-scale transport from large fires to the south/southeast.

Browell, E. V.↗
NASA NTRS1988

Biomass-burning emissions and associated haze layers over Amazonia

The characteristics of haze layers, which were visually observed over the central Amazon Basin during many of the Amazon Boundary Layer Experiment 2A flights in July/August 1985, were investigated by remote and in situ measurements, using the broad range of instrumentation and sampling equipment on board the Electra aircraft. It was found that these layers strongly influenced the chemical and optical characteristics of the atmosphere over the eastern Amazon Basin. Relative to the regional background, the concentrations of CO, CO2, O3, and NO were significantly elevated in the plumes and haze layers, with the NO/CO ratio in fresh plumes much higher than in the aged haze layers. The haze aerosol was composed predominantly of organic material, NH4, K(+), NO3(-), SO4(2-), and organic anions (formate, acetate, and oxalate).

Andreae, M. O.↗
NASA NTRS1990

July 16, 1987 revisited: Lessons for modelers

A cross pattern was flown by the NCAR Electra in the restricted air space around San Nicolas Island (SNI). There was available a LANDSAT image coincident with the mission. The variability of cloud thickness along the flight track is discussed. The evidence points to variability in the water vapor content above the inversion as the controlling factor. This compounds the difficulty of parameterizing these clouds in General Circulation Models (GCMs). The importance of specifying correctly the upper boundary condition in cloud models is stressed. Particularly, in GCMs, calculating the humidity in the lower layers of the model is crucial for successful parameterization of marine stratocumulus clouds.

Hanson, Howard P.↗