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At least 343 records · Page 19

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NASA NTRS1980

Shuttle-era experiments in the area of plasma flow interactions with bodies in space

A new experimental approach is discussed that can be adopted for studies in the area of plasma flow interactions with bodies in space. The potential use of the Space Shuttle/Orbiter as a near-earth plasma laboratory for studies in space plasma physics and particularly in solar system plasmas is discussed. This new experimental approach holds great promise for studies in the supersonic and sub-Alfvenic flow regime which has applications to the motion of natural satellites around their mother planets in the solar-system (e.g., the satellite Io around the planet Jupiter). A well conceived experimental and theoretical program can lead to a better physical understanding regarding the validity and range of applicability of using gasdynamic, kinetic, and fluid approaches in describing collisionless plasma flow interactions with bodies in a variety of flow regimes. In addition to the above scientific aspects of the program, significant technological advances can be achieved regarding the interaction of space probes in planetary atmospheres/ionospheres and the reliability of using various plasma diagnostic devices on board spacecraft and large space platforms.

Samir, U.↗

NASA NTRS1981

The Spacelab Lyman alpha and white light coronagraphs program

The Harvard-Smithsonian Center for Astrophysics and the High Altitude Observatory have defined a joint coronagraphs experiment for a future Spacelab mission. The instrumentation package would include an ultraviolet light coronagraph to measure the intensity and profiles of spectral lines formed between 1.2 and 8 solar radii from sun center and a white light coronagraph to measure the intensity and polarization of visible light. The overall goals of the joint program are to use new coronal plasma diagnostic techniques to understand the physical processes and mechanisms operating in the solar corona, to understand the acceleration of high-speed and low-speed solar wind streams and to extrapolate this knowledge to other stars in order to help understand the physics of stellar coronae and stellar mass loss.

Kohl, J. L.↗

NASA NTRS1981

Experimental investigations of turbulence in magnetized, partially ionized plasmas

An experimental investigation of turbulent fluctuations associated with gradient cross-field and Farley-Buneman instabilities is described. The experiments are carried out in magnetized plasma columns with an imposed radial electric field. Microwave scattering and probe measurements provide the plasma diagnostics. Particular attention is given to the varying characteristics of the turbulent spectra for both potential and density as a function of neutral gas pressure.

Mikkelsen, T.↗

NASA NTRS1982

Science on the Space Shuttle

On the Space Shuttle's third flight, scientific instruments will study the electromagnetic environment with charging and electron beams. Beam plasma discharge will be studied. The plasma diagnostics package contains electromagnetic and particle sensors to study the ionosphere. An attempt will be made to establish a more accurate base of solar UV irradiance measurements with an absolute error of 10 percent or less over the wavelength region 120-400 nm. The solar flare X-ray polarimeter will observe flare X-rays emitted between 5 and 30 keV and measure their polarization as a function of time and photon energy. A photopolarimeter will help study zodiacal light, and interplanetary dust will be sampled by a section of thick aluminum foil. Plant seedlings will be grown to research the effect of near-zero gravity on lignification. A thermal canister experiment will help determine whether instruments can be maintained at a fixed temperature under varying thermal loads.

Neupert, W. M.↗

NASA NTRS1981

Radiometry using synchrotron radiation

It is possible to use synchrotron radiation from electron synchrotrons and electron storage rings as an absolute source, especially in the VUV and soft X-ray regions where other standards are difficult to find. At the NBS, an electron storage ring (SURF-II) has been used to calibrate spectrometers and photometers utilized in solar and aeronomy research and in fusion plasma diagnostics. The radiation incident on these spectrometers can be calculated to uncertainties of 3%, and a technique to exactly determine the number of electrons orbiting in the ring is currently being developed to reduce this uncertainty. Detector calibrations between 5 and 55 nm are routinely performed at SURF-II and transfer standard detectors with 6-10% uncertainties over the range 5-254 nm are supplied.

Saloman, E. B.↗

NASA NTRS1983

OSS-1 - A pathfinder mission for space science on Shuttle

On the third Shuttle flight (STS-3), the Orbiter carried a payload of nine scientific instruments. The payload was designated OSS-1 because the program was originaly managed by the Office of Space Science. The OSS-1 objectives are discussed, taking into account the Plasma Diagnostics Package, a study concerned with vehicle charging and potential, the Thermal Canister Experiment, the Solar Flare X-ray Polarimeter, the Solar Ultraviolet Spectral Irradiance Monitor, the study of the influence of weightlessness on lignification in developing plant seedlings, the Microabrasion Foil Experiment, the Contamination Monitor Package, and a study of the characteristics of the Shuttle/Spacelab induced atmosphere. The OSS-1 payload was launched on STS-3 on March 22, 1982.

Neupert, W. M.↗

NASA NTRS1983

Plasma jet effects on the ionospheric plasma

Heavy ion beams were injected into the ionospheric plasma (experiments ARCS 1 and ARCS 2). In ARCS 1, operation of a 25eV argon ion source, mounted on a plasma diagnostic payload, produced an accelerated electron population; broadband electric field turbulence; large, spin synchronized electric field perturbations; and depletions of thermal ions. In ARCS 2, the ion source was deployed upward along the local magnetic field direction away from the diagnostic payload, and observed effects are contained within several meters of the ion source. However, enhanced wave levels near the LHR frequency are observed at distances up to 1 km, as are the injected ions themselves. A measurement of the dominant wavelength of the enhanced waves is consistent with an inference based upon the accelerated electron population seen in ARCS 1. This electron population is not evident during ARCS 2.

Moore, T. E.↗

NASA NTRS1984

The electron Echo 6 mechanical deployment systems

The Echo 6 sounding rocket payload was flown on a Terrier boosted Black Brant vehicle on March 30, 1983. The experiment requirements resulted in the new design of a rocket propelled Throw Away Detector System (TADS) with onboard Doppler radar, a free-flyer forward experiment designated the Plasma Diagnostic Package (PDP), and numerous other basic systems. The design, developmental testing, and flight preparations of the payload and the mechanical deployment systems are described.

Meyers, S. C.↗

NASA NTRS1983

Submillimeter-wave receivers - A status report

A development status assessment is presented for the work of U.S. and Western European research groups on heterodyne sub-mm receivers in the 300-1000 GHz frequency range. The applications driving sub-mm receiver and local oscillator source technologies are radio astronomy, atmospheric measurements, plasma diagnostics, and laboratory spectroscopy. Progress is concentrated in two areas, cooled Schottky diode mixers and solid state local oscillators employing frequency multipliers.

Wilson, W. J.↗

NASA NTRS1984

Radio frequency fields generated by the S-band communication link on OV102

The Space Shuttle STS-3 mission carried a Plasma Diagnostics Package (PDP) whose instrumentation included an S-band antenna and detector. The PDP was maneuvered by the Remote Manipulator System arm through a computer controlled sequence in the Orbiter's X-Z plane, above the quad and hemi S-band communications antennas. Antenna field strength measurements were conducted during transmitter high power modes, and the results were compared to ground full scale measurements and predictions. A field strength 4.8 + or - 3 dB higher than predicted is noted. This RF field is primarily due to the quad PM transmitter, whose power output of 115 W compares with 15 W for the hemi.

Murphy, G. B.↗

NASA NTRS1984

Ion resonances and ELF wave production by an electron beam injected into the ionosphere - ECHO 6

Two effects observed with electron antennas ejected from a sounding rocket launched into the ionosphere in March 1983 carrying electron beam guns are discussed. The sensor packages were ejected and travelled parallel to the vehicle trajectory. Electric potentials were measured between the single probes and a plasma diagnostic package while the gun injected electrons into the ionosphere in perpendicular and parallel 1 kHz directions. Signal pulses over the dc-1250 kHz range were detected. A kHz gun frequency caused a signal that decreased by two orders of magnitude between 45-90 m from the beam field line. However, the signal was detectable at 1 mV/m at 120 m, supporting earlier data that indicated that pulsed electron beams can cause ELF waves in space. Beam injection parallel to the magnetic field produced an 840 Hz resonance that could be quenched by activation of a transverse beam.

Winckler, J. R.↗

NASA NTRS1984

Tunable Heterodyne Receiver from 100 Micron to 1,000 Micron for Airborne Observations

Interest in high resolution spectrometers for the submillimeter wavelength range from 100 micron to 1,000 micron is mostly stimulated by molecular spectroscopy in radioastronomy and atmospheric physics, and by plasma diagnostic experiments. Schottky diodes in waveguide mixer technology and InSb-hot electron bolometers are successfully used in the 0.5 to a few millimeter range whereas tandem Fabry-Perot spectrometers combined with photoconductive detectors (Ge:Sb and Ge:Ga) are used for the 100 micron range. Recent research on heterodyne spectrometers, with Schottky diodes in an open structure mixer and a molecular laser as local oscillators, which can be used over the whole wavelength range is summarized.

Roeser, H. P.↗

NASA NTRS1984

X-ray astronomy and plasma astrophysics

X-ray astronomy studies of thin, thermal plasmas in stellar coronas, supernova remnants, and clusters of galaxies are reviewed. Plasma diagnostics for density, temperature and elemental abundance, as well as for departures from ionization equilibrium are described. These were used in analyses of data from imaging and spectroscopic intruments on the Einstein satellite. Results of these diagnostics were used to study the nature of coronal loops in RS CVn stars; the masses and abundances in Type I and Type II supernova remnants with implications for stellar evolution and the enrichment of the interstellar medium; the structure of the interstellar medium; the quantity and distribution of dark matter in galaxy halos; and the existence of cooling accretion flow in clusters.

Canizares, C. R.↗

NASA NTRS1985

Physics of the inner heliosphere: Mechanisms, models and observational signatures

The physics of the solar wind acceleration phenomena (e.g. effect of transient momentum deposition on the temporal and spatial variation of the temperature, density and flow speed of the solar wind, formation of shocks, etc.) and the resultant effects on observational signatures, particularly spectroscopic signature are studied. Phenomena under study include: (1) wave motions, particularly spectroscopic signatures are studied. Phenomena under study include:(1) wave motions, particularly Alfven and fast mode waves, (2) the formation of standing shocks in the inner heliosphere as a result of momentum and/or heat addition to the wind and (3) coronal transient phenomena where momentum and/or heat are deposited in the corona to produce transient plasma heating and/or mass ejections. Also included are the theoretical investigation of spectroscopic plasma diagnostics for the inner heliosphere and the analysis of existing Skylab and other relevant data.

Withbroe, G. L.↗

NASA NTRS1984

Microwave-enhanced thin-film deposition

The deposition of semiconducting and insulating thin films at low temperatures using microwave technology was explored. The method of plasma formations, selection of a power source, the design of the microwave plasma cavity, the microwave circuitry, impedance matching, plasma diagnostics, the deposition chamber and the vacuum system were studied.

Chitre, S.↗

NASA NTRS1985

ELF wave production by an electron beam emitting rocket system and its suppression on auroral field lines - Evidence for Alfven and drift waves

Orthogonal probes on a free-flying plasma diagnostics payload are used to study ELF electric disturbances in the auroral ionosphere that are due to the injection of powerful electron beams. Frequency spectrograms are presented for various pitch angles, pulsing characteristics, and other properties of the injected beams; the large scale DC ionospheric convection electric field is measured, together with auroral particle precipitation, visual auroral forms, and ionospheric parameters. In view of the experimental results obtained, it is postulated that the observed ELF waves are in the Alfven and drift modes, and are generated by the positive vehicle potential during beam injection.

Winckler, J. R.↗

NASA NTRS1985

Spectrum and chemical composition of the remarkable planetary nebula NGC 6537

The planetary nebula NGC 6537 appears to be an irregular bipolar object. Conventional procedures have been employed to observe the spectrum of NGC 6537 with the image dissector scanner at the Lick 3-m telescope. Both red- and green-sensitive tubes were employed in order to cover the spectrum from the practical UV limit near lambda 3300 A to the near-infrared limit near lambda 8600 A. The instrumental response function was determined on the basis of the observation of suitable comparison stars. On Oct. 23, 1984, observations with the International Ultraviolet Explorer (IUE) were obtained. A table containing the optical region spectrum of NGC 6537 is presented along with a table providing the UV fluxes, a table listing the ionic concentrations, and a table with data describing the chemical composition of NGC 6537. Attention is given to theoretical models and the determination of the nebular chemical composition, and aspects of plasma diagnostics.

Feibelman, W.↗

NASA NTRS1985

Waterhole auroral arc modification experiments Electrodynamic response

The Waterhole series of experiments, which tested current theories of the electrodynamic structure of auroral arcs, is discussed. In these experiments, the current-carrying capability of the ionospheric plasma was modified by the explosive release of a large number of reactive molecules in the ionospheric F region, with the net effect of reducing the local plasma density over spatial scales comparable to the auroral forms. The response of the aurora to this perturbation was monitored directly by plasma diagnostic instruments on the rocket carrying the explosive release and indirectly from the ground by various photometric and imaging devices. Model predictions of the perturbation induced by the two releases are summarized, and the rocket-borne and ground-based instrumentation is described. Results from both flights are summarized, and a theoretical model is presented which relates the differences in observed response to the topological relationship between the releases and the auroral form.

Whalen, B. A.↗