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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 667 records · Page 37
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Demonstration of high sensitivity laser ranging system

We report on a high sensitivity semiconductor laser ranging system developed for the Gravity and Magnetic Earth Surveyor (GAMES) for measuring variations in the planet's gravity field. The GAMES laser ranging instrument (LRI) consists of a pair of co-orbiting satellites, one which contains the laser transmitter and receiver and one with a passive retro-reflector mounted in an drag-stabilized housing. The LRI will range up to 200 km in space to the retro-reflector satellite. As the spacecraft pair pass over the spatial variations in the gravity field, they experience along-track accelerations which change their relative velocity. These time displaced velocity changes are sensed by the LRI with a resolution of 20-50 microns/sec. In addition, the pair may at any given time be drifting together or apart at a rate of up to 1 m/sec, introducing a Doppler shift into the ranging signals. An AlGaAs laser transmitter intensity modulated at 2 GHz and 10 MHz is used as fine and medium ranging channels. Range is measured by comparing phase difference between the transmit and received signals at each frequency. A separate laser modulated with a digital code, not reported in this paper, will be used for coarse ranging to unambiguously determine the distance up to 200 km.

Millar, Pamela S.↗
NASA NTRS1998

Book Review: Physics of the Space Environment

Space physics, narrowly defined as the study of Earth's plasma environment, has had an identity crisis throughout its relatively brief existence as a discipline. - The limited and often serendipitous nature of the data requires the research style of an astrophysicist. However, the in situ observations and instrumentation that are central to the field are quite different from the remote observations and instrumentation of astronomy. Compared to neutral gases, the wealth of additional phenomena and the complexity associated with magnetized plasmas and their interaction leaves little in common with the atmospheric scientist. Although the phenomena studied in space physics are ultimately important to astrophysics, the intimate measurements of plasma properties provide a greater commonality with the plasma physicist. Space physics has experienced something of a renaissance in the past few years. The interdisciplinary umbrella "Solar-Terrestrial Physics" or "Sun-Earth Connection" has stimulated an increasing interaction of space physicists, solar physicists and atmospheric scientists. Spectacular images of the Sun from Yohkoh and SOHO and solar-activity-related damage to communications satellites have increased the public's awareness of and interest in "space weather". The dangers of energetic particles and currents in space to technological systems and to future space exploration have elevated space physics observations from interesting scientific measurements that can be included on a space probe to critically important measurements that must be made.

Holman, Gordon D.↗
NASA NTRS2001

Development of a Polarimeter for Magnetic Field Measurements in the Ultraviolet

This paper will describe the polarizing optics that are being developed for an ultraviolet magnetograph (SUMI) which will be flown on a sounding rocket payload. With a limited observing program, the polarizing optics were optimized to make simultaneous observation at two magnetic lines CIV (155nm) and MgII (280). This paper will give a brief overview of the SUMI instrument, will describe the polarimeter that will be used in the sounding rocket program and will present some of the measurements that have been made on the (SUMI) polarization optics.

West, Edward↗
NASA NTRS2002

Timekeeping for the Space Technology 5 (ST-5) Mission

Space Technology 5, or better known as ST-5, is a space technology development mission in the New Millennium Program (NMP) and NASA s first experiment in the design of miniaturized satellite constellations. The mission will design, integrate and launch multiple spacecraft into an orbit high above the Earth s protective magnetic field known as the magnetosphere. Each spacecraft incorporates innovative technology and constellation concepts which will be instrumental in future space science missions. A total of three ST-5 spacecraft will be launched as secondary payloads into a highly elliptical geo-synchronous transfer orbit, and will operate as a 3-element constellation for a minimum duration of 90 days. In order to correlate the time of science measurements with orbit position relative to the Earth, orbit position in space (with respect to other objects in space) and/or with events measured on Earth or other spacecraft, accurate knowledge of spacecraft and ground time is needed. Ground time as used in the USA (known as Universal Time Coordinated or UTC) is maintained by the U.S. Naval Observatory. Spacecraft time is maintained onboard within the Command and Data Handling (C&DH) system. The science requirements for ST-5 are that spacecraft time and ground time be correlatable to each other, with some degree of accuracy. Accurate knowledge of UTC time on a spacecraft is required so that science measurements can be correlated with orbit position relative to the Earth, orbit position in space and with events measured on Earth or other spacecraft. The most crucial parameter is not the clock oscillator frequency, but more importantly, how the clock oscillator frequency varies with time or temperature (clock oscillator drift). Even with an incorrect clock oscillator frequency, if there were no drift, the frequency could be assessed by comparing the spacecraft clock to a ground clock during a few correlation events. Once the frequency is accurately known, it is easy enough to make a regular adjustment to the spacecraft clock or to calculate the correct ground time for a given spacecraft clock time. The oscillator frequency, however, is temperature dependent, drifts with age and is affected by radiation; hence, repeated correlation measurements are required.

Raphael, Dave↗
NASA NTRS2012

Calorimetric Low-Temperature Detectors for X-Ray Spectroscopy on Trapped Highly-Charged Heavy Ions

The application of Calorimetric Low-Temperature Detectors (CLTDs) has been proposed at the Heavy-Ion TRAP facility HITRAP which is currently being installed at the Helmholtz Research Center for Heavy Ion Research GSI. This cold ion trap setup will allow the investigation of X-rays from ions practically at rest, for which the excellent energy resolution of CLTDs can be used to its full advantage. However, the relatively low intensities at HITRAP demand larger solid angles and an optimized cryogenic setup. The influence of external magnetic fields has to be taken into account. CLTDs will also be a substantial part of the instrumental equipment at the future Facility for Antiproton and Heavy Ion Research (FAIR), for which a wide variety of high-precision X-ray spectroscopy experiments has been proposed. This contribution will give an overview on the chances and challenges for the application of CLTDs at HITRAP as well as perspectives for future experiments at the FAIR facility.

Kilbourne, Caroline↗
NASA NTRS2011

Image Quality of the Helioseismic and Magnetic Imager (HMI) Onboard the Solar Dynamics Observatory (SDO)

We describe the imaging quality of the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO) as measured during the ground calibration of the instrument. We describe the calibration techniques and report our results for the final configuration of HMI. We present the distortion, modulation transfer function, stray light,image shifts introduced by moving parts of the instrument, best focus, field curvature, and the relative alignment of the two cameras. We investigate the gain and linearity of the cameras, and present the measured flat field.

Solar Dynamics Observatory↗
NASA NTRS2017

CLASP2: High-Precision Spectro-Polarimetery in Mg II h & k

The international team is promoting the CLASP2 (Chromospheric LAyer Spectro-Polarimeter 2) sounding rocket experiment, which is the re-flight of CLASP (2015). In this second flight, we will refit the existing CLASP instrument to measure all Stokes parameters in Mg II h k lines, and aim at inferring the magnetic field information in the upper chromosphere combining the Hanle and Zeeman effects. CLASP2 project was approved by NASA in December 2016, and is now scheduled to fly in 2019.

spectropolarimetry↗
NASA NTRS2019

Development of Large-Scale Magnetic Calorimeter Arrays

We describe performance of large-scale arrays of metallic magnetic calorimeters (MMCs) we are developing to meet requirements of the Lynx X-ray Microcalorimeter (LXM) instrument in the astrophysics mission concept Lynx. We have fabricated prototypes with 55,800 x-ray pixels thermally connected to 5,688 MMC sensors. Subarrays demonstrate three types of pixels, which have different energy and spatial resolution goals in LXM. Pixel pitch is 50 or 25 µm. For two subarrays, use of position sensitive detectors, in a "hydra" configuration with 25 x-ray absorbers per sensor, helps achieve a large focal plane by increasing pixel count relative to readout channels. Since each absorber has a different thermal link to its sensor, it generates a different pulse shape and enables discrimination of pixel position. Superconducting wiring from all sensors was brought out to the perimeter of the overall array using multiple buried metal layers planarized by Chemical Mechanical Planarization to achieve high critical current, low inductance, and high fabrication yield. An automated, algorithmic approach was used to layout the complex wiring pattern. For readout with existing small arrays of Superconducting Quantum Interference (SQUID) amplifiers, 112 selected pixels were connected to wire bond pads. In hydras, we successfully identified 25 pulse shapes using rise-time and pulse height. Pulse shapes were similar to simulations. We measured noise and responsivity to substrate temperature and applied x-ray pulses. While we designed sensors to have high inductance to relative to stray inductance of wiring, we had only mismatched (lower input inductance) SQUIDs available in our current apparatus, giving non-optimized resolution. We compared measured and calculated energy resolutions. We have the required sensitivity to reach < 3 eV FWHM resolution for 6 keV x-rays, required for the LXM Main Array, and the ability to discriminate the 25 different absorber pixels down to energies < 300 eV.

microcalorimeters↗
NASA NTRS1990

Installing scientific instruments into a cold LHe dewar - The Gravity Probe B approach

Gravity Probe B is an orbital test of Einstein's general theory of relativity using gyroscopes. The precession of the gyroscopes will measure both the geodetic effect (6.6 arcsec/yr) through the curved space-time surrounding the earth and the motional effect (0.042 arcsec/yr) due to the rotating earth dragging space-time around with it. To achieve the extraordinary accuracies needed to measure these small precessions, it is necessary to have the gyroscopes operating in the following environments: a vacuum of less than 10 exp -10 torr; an acceleration level of less than 10 exp -10 g's; a magnetic field of less than 10 exp -7 gauss; and a temperature near 2 K. This paper discusses designs that allow scientific instruments to be installed into a dewar at 4.2 K. Methods for structurally supporting the instruments, transferring heat across joints at low temperature in vacuum, and excluding air during the insertion process are discussed. The structural support method is designed for Shuttle launch loads.

Parmley, Richard T.↗
NASA NTRS2003

Dayside Proton Aurora: Comparisons between Global MHD Simulations and Image Observations

The IMAGE mission provides a unique opportunity to evaluate the accuracy of current global models of the solar wind interaction with the Earth's magnetosphere. In particular, images of proton auroras from the Far Ultraviolet Instrument (FUV) onboard the IMAGE spacecraft are well suited to support investigations of the response of the Earth's magnetosphere to interplanetary disturbances. Accordingly, we have modeled two events that occurred on June 8 and July 28, 2000, using plasma and magnetic field parameters measured upstream of the bow shock as input to three-dimensional magnetohydrodynamic (MHD) simulations. This paper begins with a discussion of images of proton auroras from the FUV SI-12 instrument in comparison with the simulation results. The comparison showed a very good agreement between intensifications in the auroral emissions measured by FUV SI-12 and the enhancement of plasma flows into the dayside ionosphere predicted by the global simulations. Subsequently, the IMAGE observations are analyzed in the context of the dayside magnetosphere's topological changes in magnetic field and plasma flows inferred from the simulation results. Finding include that the global dynamics of the auroral proton precipitation patterns observed by IMAGE are consistent with magnetic field reconnection occurring as a continuous process while the iMF changes in direction and the solar wind dynamic pressure varies. The global simulations also indicate that some of the transient patterns observed by IMAGE are consistent with sporadic reconnection processes. Global merging patterns found in the simulations agree with the antiparallel merging model. though locally component merging might broaden the merging region, especially in the region where shocked solar wind discontinuities first reach the magnetopause. Finally, the simulations predict the accretion of plasma near the bow shock in the regions threaded by newly open field lines on which plasma flows into the dayside ionosphere are enhanced. Overall the results of these initial comparisons between global MHD simulation results and IMAGE observations emphasize the interplay between reconnection and dynamic pressure processes at the dayside magnetopause. as well as the intricate connection between the bow shock and the auroral region.

Berchem, J.↗
NASA NTRS2006

CIV Vacuum Ultraviolet Fabry-Perot Interferometers for Transition-Region Magnetography

The vacuum ultraviolet region allows remote sensing of the upper levels of the solar atmosphere where the magnetic field dominates the physics. Obtaining an imaging interferometer that observes the transition region is the goal of this program. This paper gives a summary of our instrument development program (1998-2005) for a high-spectral-resolution, piezoelectric tunable Vacuum Ultraviolet Fabry-Perot Interferometer (VUV FPI) for obtaining narrow-passband images, magnetograms, and Dopplergrams of the transition region emission line of CN (155nm). A VUV interferometer will allow us to observe the magnetic field, flows, and heating events in the mid-transition region. The MSFC VUV FPI has measured values of FWHM approx. 9pm, FSR approx. 62pm, finesse approx. 5.3 and transmittance approx. 50% at 157nm. For the measurements, the University of Toronto's F2 eximer laser was used as an appropriate proxy for CIV 155nm. This has provided the first tunable interferometer with a FWHM compatible to VUV filter magnetograph.

Gary, G. Allen↗
NASA NTRS1987

Birkeland currents - Recent contributions from satellite magnetic field measurements

The important role that field-aligned Birkeland currents play in solar terrestrial coupling processes has been known from satellite observations for twenty years. Many satellite have been launched since the last Solar-Terrestrial Symposium with instruments capable of investigating the characteristics of Birkeland currents and their relationship to visible and UV auroral forms, particle precipitation, and convection flow patterns. An important result that has emerged is the close relationship between large-scale Birkeland currents and the orientation of the interplanetary magnetic field. These observations emphasize the fact that Birkeland currents are involved in a wide range of space plasma processes which range from small-scale ionospheric instabilities and irregularities to global scale energy coupling processes between the magnetosphere and solar wind.

Potemra, T. A.↗
NASA NTRS1985

Recent studies of magnetic canopies

Two current studies are described which stem from Giovanelli's seminal studies of the spreading of chromospheric fields near active regions and active-region network. First, improved observational techniques are described for obtaining magnetograms in the Ca II 8542 A, Fe I 8688 A, and C I 9111 A lines which at least in principle allow for more accurate treatment of instrumental noise and allow better inference of field orientation. Second, a generalized response function is developed for calculating theoretical magnetograph signals from arbitrary line-of-sight variations of magnetic field, and initial applications to two-dimensional, potential-field models of network fields are described. Preliminary indications are that potential-field models can better explain the presence of low-lying, diffuse horizontal fields than can thin flux-tube models, but fail to predict a differential response between the different lines.

Jones, H. P.↗
NASA NTRS2014

X-Ray Polarization Capabilities of a Small Explorer Mission

X-ray polarization measurements hold great promise for studying the geometry and emission mechanisms in the strong gravitational and magnetic fields that surround black holes and neutron stars. In spite of this, the observational situation remains very limited; the last instrument dedicated to X-ray polarimetry flew decades ago on OSO-8, and the few recent measurements have been made by instruments optimized for other purposes. However, the technical capabilities to greatly advance the observational situation are in hand. Recent developments in micro-pattern gas detectors allow use of the polarization sensitivity of the photo-electric effect, which is the dominant interaction in the band above 2 keV. We present the scientific and technical requirements for an X-ray polarization observatory consistent with the scope of a NASA Small Explorer (SMEX) mission, along with a representative catalog of what the observational capabilities and expected sensitivities for the first year of operation could be. The mission is based on the technically robust design of the Gravity and Extreme Magnetism SMEX (GEMS) which completed a Phase B study and Preliminary Design Review in 2012. The GEMS mission is enabled by time projection detectors sensitive to the photo-electric effect. Prototype detectors have been designed, and provide engineering and performance data which support the mission design. The detectors are further characterized by low background, modest spectral resolution, and sub-millisecond timing resolution. The mission also incorporates high efficiency grazing incidence X-ray mirrors, design features that reduce systematic errors (identical telescopes at different azimuthal angles with respect to the look axis, and mounted on a rotating spacecraft platform), and a moderate capability to perform Target of Opportunity observations. The mission operates autonomously in a low earth, low inclination orbit with one to ten downlinks per day and one or more uplinks per week. Data and calibration products will be made available through the High Energy Astrophysics Science and Archival Research Center (HEASARC).

GEMS↗
NASA NTRS1983

The Giotto magnetic field investigation

The Giotto spacecraft will carry sensors for investigating the interplanetary magnetic field while en route and the interaction between the solar wind magnetoplasma and Halley's Comet neutral gas outflow during close approach. Giotto will carry an outboard biaxial fluxgate system and inboard electronics. The instrumentation draws 1.2 kW and weighs 1.31 kg. Sampling rates will be 28/sec during close encounter, covering selectable ranges from 16 nT to 65,535 nT. In-flight calibration techniques are under development to ensure magnetic cleanliness will be obtained. Measurements are also planned of the inbound bow shock, the magnetosheath and the cometary ionopause. The data will be collected as close as 1000 km from the comet surface.

Neubauer, F. M.↗
DOE OSTI2025

Inelastic Neutron Scattering Data for Ba₃Zn(Ru₀.₁Sb₁.₉)O₉

This dataset contains inelastic neutron scattering measurements on the magnetically dilute compound Ba₃Zn(Ru₀.₁Sb₁.₉)O₉, collected at the Spallation Neutron Source using the Cold Neutron Chopper Spectrometer (CNCS) and the SEQUOIA Fine-Resolution Fermi Chopper Spectrometer. The sample consists of nominally 5% magnetic Ru⁵⁺ ions (S = 3/2) randomly substituted into a diamagnetic Sb⁵⁺ matrix. Measurements were performed at base temperature (2–5 K) and 300 K using multiple incident energies (1.00, 3.32, 12.0, and 100 meV) to resolve magnetic excitations from isolated monomers and small Ru clusters (dimers, trimers, etc.). The dataset includes raw event-mode files, momentum- and energy-resolved spectra, and supporting metadata for instrument configuration, sample environment, and reduction parameters.

36 MATERIALS SCIENCE↗
NASA NTRS1979

Initial ISEE magnetometer results - Shock observation

A selection of early measurements is used to illustrate the three advantages brought by ISEE to the study of natural collisionless shocks. These advantages are the ability to resolve most space/time ambiguity by means of simultaneous two-point measurements, instrumentation to make comprehensive field and particle observations covering all important quantities, and the capacity to record data at high time resolution. Magnetic-field records from shocks of various types are presented; the types of shock include laminar, supercritical, quasi-perpendicular, high-beta, and quasi-parallel. The spacing of the two spacecraft and the resolution of the system are employed to develop numerous kinematic descriptions of the shocks and the waves that compose and surround them. Data from a single particle experiment are correlated with field data for three cases to demonstrate the important role of comprehensive instrumentation.

Russell, C. T.↗