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At least 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

The Giotto ion mass spectrometer

The Giotto Ion Mass Spectrometer (IMS) consists of two sensors: one optimized for the outer and the other for the inner coma, with each obtaining complementary information in the region for which it is not optimized. The outer coma is characterized by the interaction between solar wind and comentary plasmas, the inner coma by the outflow of cometary neutrals and their ionization products. Both sensors feature mass imaging characteristics, permitting simultaneous measurements of several ion species by multidetector arrays. Resultant mass-per-charge resolution is greater than or = 20. Energy per charge, and the elevation and aximuth of incident ions are measured. Calibration and in-flight solar-wind data show that the IMS will meet its scientific goals for the Halley encounter.

Balsiger, H.↗
NASA NTRS1985

Deformation of the heliospheric current sheet

A kinematic analysis of the previously neglected effect of velocity inhomogeneity on the topology of the heliospheric current sheet in a radially flowing solar wind shows how the originally smooth current sheet becomes 'ruffled'. In the highly idealized case of a totally uniform, radial, steady solar wind, the shape of the current sheet is independent of distance from the sun. However, the real solar wind is inhomogeneous; the velocity varies from point to point along the current sheet, causing a distortion in the current sheet of progressively greater amplitude with increasing distance from the sun. This is true even for purely radial flow. Significant and observable distortion is produced by relatively small gradients in velocity; thus to predict or understand the shape of the heliospheric current sheet it is essential to know the solar wind in which the current sheet is embedded. Examples are given of mild velocity gradients which demonstrate the principles, the magnitude, and the character of the effect; deformation of the actual heliospheric current sheet in the highly variable solar wind is expected to be of far greater amplitude and complexity than in the simplified, tutorial examples. A new expression for the inclination of the current sheet as a function of velocity inhomogeneity and distance from the sun that is easily applied to the interpretation of solar wind data is also derived.

Suess, S. T.↗
NASA NTRS1985

Flight tests and preliminary aerodynamic parameter extraction of an externally piloted vehicle aircraft model

Model aircraft flight test investigations have been undertaken to develop a low cost flight data acquisition system and to evaluate aerodynamic parameter estimation techniques. The externally piloted vehicles (EPVs) used are instrumented with sensors measuring acceleration, angular rates, angles of attack and sideslip, flight path velocity, and control deflections. Measured state variables are downlink telemetered to a ground-based real time flight data acquisition system; the data thus recorded are used by flight test engineers and EPV pilots to monitor conditions and aid in piloting tasks. Attention is given to comparisons of F-16 EPV data with wind tunnel data.

White, E. R.↗
NASA NTRS1986

Wind profiler demonstration system

The National Oceanic and Atmospheric Administration (NOAA) has started procurement of a 30-station demonstration network of Doppler radar wind profilers to be deployed in the central United States by 1989. The purposes of this demonstration network are: (1) to assess the impact of a large wind profiler network on meteorological forecasting; (2) to test wind profiler hardware designed specifically for commercial production and widespread deployment; and (3) to provide wind data for research programs involving weather phenomena in the central United States.

Chadwick, R. B.↗
NASA NTRS1986

Mean zonal winds on Venus from Doppler tracking of the Vega balloons

Doppler measurements of the two Vega balloons yield the following provisional estimates for the mean zonal wind velocity at the 53-54 km level in the Venus atmosphere: 69 + or - 1 m/sec for Vega 1 and 66 + or - 1 m/sec for Vega 2, with westward flow. The wind data show a perturbation which might be an evidence of solar tides.

Andreev, R. A.↗
NASA NTRS1987

Mapping global winds with satellite borne Doppler lidar - A plan

The application of the Laser Atmospheric Wind Sounder to the EOS and Space Station is proposed. The use of pulsed, CO2 Doppler lidar to measure wind is described. The design requirements for a Doppler lidar operating in space, and the need to study the global distribution of naturally occurring atmospheric aerosols are discussed. The space-based Doppler lidar wind data will be useful for improving the skill of numerical weather predictions, for studying large-scale atmospheric circulation and climate dynamics, and for analyzing global biogeochemical and hydrological cycles.

Fitzjarrald, D.↗
NASA NTRS1987

Shock overshoots revisited

The ISEE 1 and 2 magnetometer and solar wind data for about 65 quasi-perpendicular bow shocks were used to investigate the role played by low-frequency turbulence in the determination of magnetic field overshoots in collisionless shock waves. Overshoots calculated from both high-resolution data and data averaged to eliminate the effects of turbulence exhibited similar behavior, but the overshoots calculated from the averaged data were generally lower by a factor of 2. Moreover, the size of overshoots calculated from the high-resolution data increased much more strongly with Mach number than that of overshoots calculated from averaged data. The difference between overshoots measured by the two sets of data was generally consistent with the presence of a component of overshoot magnitude due to low-frequecy turbulence.

Mellott, M. M.↗
NASA NTRS1988

Airborne Doppler lidar wind field measurements of waves in the lee of Mount Shasta

Doppler lidar wind data obtained along one leg of a race track traverse around Mount Shasta are presently studied to establish their value and limitations for the study of orographic flows, as well as to evaluate the relative usefulness of a linear model in the analyses of the observed fields-of-motion. The model successfully reproduced the observed downstream lee of positive horizontal divergence which embedded spatially irregular waves, but the amplitudes of the model downstream divergence is smaller than the observations by a factor of two.

Blumen, William↗
NASA NTRS1988

Doppler lidar wind measurements on the EOS - LAWS

This paper discusses the efforts currently underway to prepare for the deployment of the Laser Atmospheric Wind Sounder (LAWS) instrument on an Earth Observing System (EOS) polar orbiter and on the Space Station. Attention is given to the measurement techiques, which include ground-based and airborne measurements in the atmosphere, and to the scientific and the technical issues being addressed. Global wind profiles obtained with the LAWS will effect dramatic improvement in numerical weather prediction and will be useful in determining the midtroposphere steering currents that are important in hurricane track forecasts. The global wind data will also provide information on large-scale atmospheric circulation and climate dynamics and on biogeochemical and hydrologic cycles.

Fitzjarrald, Daniel E.↗
NASA NTRS1988

Windshear detection and avoidance - Airborne systems perspective

The generalized windshear hazard index presently defined is derived from aircraft-position wind data and remotely sensed data obtained along the extended flight path by such candidate sensor technologies as microwave Doppler radar, Doppler lidar, and IR radiometry. Attention is given here to the results of a comparative evaluation of CO2 and Ho:YAG lidar sensor-employing windshear-detection systems, over a range 1-3 km ahead of the aircraft (corresponding to 15-45 sec of warning time). While the technology for a 10.6-micron CO2 lidar system is available, an optimum 2-micron REE laser crystal-based system remains to be developed.

Bowles, Roland L.↗
NASA NTRS1988

A solar-wind 'trigger' for the outer heliosphere radio emissions and the distance to the terminal shock

The solar wind data from the plasma science experiment on the Voyager spacecraft are examined to search for the source of the 2 to 3 kHz radio noise detected in the outer heliosphere. It is found that two anomalous high speed streams passed Voyager 2 before the noise was initially observed. It is suggested that the interaction of these streams with the terminal shock is responsible for the more intense emission. Using a time-of-flight argument, the distance to the shock is estimated at about 70 AU-140 AU. The larger value is consistent with an estimate using Voyager data and a standard pressure-balance argument.

Mcnutt, Ralph L., Jr.↗
NASA NTRS1988

Analysis of in-flight winds for shuttle Mission STS 51-L

Television photos of smoke plumes are analyzed to estimate meridional wind shear on the space shuttle Challenger associated with the accident of Mission 51-L. Gust velocities were obtained by detailed examination of the debris trails. The shuttle exhaust trail was used to establish altitudes of significant features in the photographs. Wind data obtained from the photographs compare favorably with data obtained from a rawinsonde released 9 min after the launch of the shuttle.

Fichtl, George H.↗
NASA NTRS1988

Adapting the NSCAT data system to changing requirements

The data system of the spaceborne eight-beam NASA scatterometer for measuring ocean backscatter is a nonreal-time ground-based science data processing system which inputs backscatter telemetry, processes the data into wind vectors, and archives and distributes the wind vector data and other products. Special attention is given to changes to the baseline design intended to meet new requirements for the data granularity, the data needs of the science team receiving the data, and the telemetry data source.

Benada, J. R.↗
NASA NTRS1989

Remote sensing of the termination of the solar wind via in situ plasma measurements

Since 1983 the Plasma Wave experiments on the two Voyager spacecraft have detected low frequency radio noise in the outer heliosphere which has been postulated to emanate from the terminal shock of the solar wind or, possibly, from the heliopause itself. The solar wind data from the Plasma Science experiment on the Voyager spacecraft are studied to search for correlations with these radio emissions. It is found that two anomalous high speed streams passed Voyager 2 in late 1982 and early 1983 and it is suggested that the interaction of the streams with the heliospheric terminal shock is responsible for the generation of the most intense radio noise observed later in the same year. If the stream speeds did not decrease in traveling to the interaction region, that region is about 135 AU from the sun. This is consistent with previous estimates of the distance to the inner heliospheric shock.

Mcnutt, R. L., Jr.↗
NASA NTRS1991

MEGASODAR experiment

SODAR application to wind shear and wake vortex detection is described. A commercial phase array SODAR line was developed and operated at Roissy International Airport for a few days. Some radial wind data are presented. Even though this system was not optimized for such application, it showed ranges of about 800 m for an averaging time of 10 min and an elevation angle of 20 deg. Some strong echo regions are present in the data and seem to be related to wake vortex.

Donzier, Alain↗
NASA NTRS1990

A simple inertial model for Neptune's zonal circulation

Voyager imaging observations of zonal cloud-tracked winds on Neptune revealed a strongly subrotational equatorial jet with a speed approaching 500 m/s and generally decreasing retrograde motion toward the poles. The wind data are interpreted with a speculative but revealingly simple model based on steady gradient flow balance and an assumed global homogenization of potential vorticity for shallow layer motion. The prescribed model flow profile relates the equatorial velocity to the mid-latitude shear, in reasonable agreement with the available data, and implies a global horizontal deformation scale L(D) of about 3000 km.

Allison, Michael↗
NASA NTRS1990

Observed mid-to-high latitude interchange of atmospheric angular momentum and some implications

Graphic illustration of midlatitude interchange of atmospheric angular momentum between distant regions is presented. An examination is conducted of the global distribution of atmospheric angular momentum during 1977-1978 and 1982-1983 in order to identify evidence of prominent short-term interchanges of relavitive atmospheric angular momentum between mid and high latitude zones in both hemispheres. Thirty-day detrended angular momentum time series, prepared from the NMC global zonal wind data, are examined in latitude bands. The results confirm that momentum can be selectively redistributed between tropical, temperate, and high latitudes in patterns indicative of the development and dissipation of interacting regions, described variously in studies on the index cycle, seesaws, and telecommunications.

Taylor, H. A., Jr.↗
NASA NTRS1991

Spaceborne radar measurement of wind velocity over the ocean - An overview of the NSCAT scatterometer system

Scatterometry and scatterometer design issues are reviewed. The design of the NASA Scatterometer (NSCAT) to be flown on the Japanese ADEOS mission is presented. Building on Seasat experience, the NSCAT system includes several enhancements, such as three antenna azimuths in each of two swaths, and an onboard digital Doppler processor to allow backscatter measurements to be colocated everywhere within the orbit. These enhancements will greatly increase the quality of the NSCAT wind data. The ground processing of data is discussed, and scatterometers of the next decade are briefly described.

Naderi, F. M.↗