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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Simulations of the sun's polar magnetic fields during sunspot cycle 21

Regarding new bipolar magnetic regions as sources of flux, the evolution of the radial component of the solar photospheric magnetic field is simulated during 1976-1984, and the corresponding evolution of the line-of-sight polar fields as seen from earth is derived. The observed timing and strength of the polar-field reversal during cycle 21 can be accounted for by supergranular diffusion alone, for a diffusion coefficient of 800 sq km/sec. For an assumed 300 sq km/sec rate of diffusion, on the other hand, a poleward meridional flow with a moderately broad profile and a peak speed of 10 m/s reached at about 5 deg latitude is required to obtain agreement between the simulated and observed fields. Such a flow accelerates the transport of following-polarity flux to the polar caps, but also inhibits the diffusion of leading-polarity flux across the equator. For flows faster than about 10 m/s, the latter effect dominates, and the simulated polar fields reverse increasingly later and more weakly than the observed fields.

Devore, C. Richard↗
NASA NTRS1994

A new component of Jovian kilometric radio emission

Evidence is presented for a new Jovian radio emission component in the frequency range from approximately 40 to approximately 200 kHz observed during the Ulysses-Jupiter outbound pass at high Jovian southern latitudes along the dusk terminator. The new radio component (referred to as sKOM) occurs in the same frequency range as the observed broadband kilometric (bKOM) radio emission, but its characteristics are distinctly different. It has the opposite polarization, is about 100 times weaker, and has a characteristically smooth intensity profile. It is consistently observed in the longitudinal range from approximately 120 degs to approximately 230 degs central meridian longitude, where the intermittent bKOM is often absent, and is found to originate in the Jovian magnetosphere about 5R(sub j) from Jupiter and at a latitude of about 35 deg S. Its observed right-hand circular polarization suggests that it is generated in the O mode in the source region.

Reiner, M. J.↗
NASA NTRS1974

Energy input to the lower thermosphere

The asymmetry in solar heat input to the upper atmosphere at the solstice, and the asymmetry in atomic oxygen production, are largely compensated by a large scale wind system towards the winter polar region. At magnetically disturbed times, atmospheric composition at high winter latitudes changes in such a way as to indicate that polar region heating by magnetic variations, energetic particle inputs, and current systems is more intense than solar heating at low latitudes, thus leading to a reversal of the normal pattern of upper atmospheric circulation. Uncertainties in the intensity of solar radiation responsible for upper atmospheric heating and oxygen dissociation, and uncertainties in the degree of oxygen dissociation in the upper atmosphere, are such that the average rates of eddy mixing may be significantly lower than frequently assumed for the lower thermosphere.

Johnson, F. S.↗
NASA NTRS1998

Polar Cap Plasma and Convection

This presentation will describe the character of the polar cap plasma in 10% AGU Spring 1998 particular the convection velocities at the perigee (about 1.8 Re) and apogee( about 8.9 Re) of Polar in relationship to Interplanetary Magnetic Field (IMF) and solar wind parameters. This plasma is thought to be due to several sources; the polar wind, cleft ion fountain, and auroral outflow. The plasma in the polar cap tends to be mostly field-aligned. At any given point in the polar cap, this plasma could be from a different regions since convection of magnetic field lines can transport this material. it is quite difficult to study such a phenomena with single point measurements. Current knowledge of the polar cap plasma obtained by in situ measurements will be presented along with recent results from the Polar mission. This study also examines the direct electrical coupling between the magnetosphere and ionosphere by comparing convection velocities measured by the Thermal Ion Dynamics Experiment (TIDE) and Magnetic Field Experiment (MFE) instruments in magnetosphere and measurements of the ionosphere by ground-based radars. At times such a comparison is difficult because the Polar satellite at apogee spends a large amount of time in the polar cap which is a region that is not coverage well by the current SuperDam coherent radars. This is impart due to the lack of irregularities that returns the radar signal.

Elliott, Heather A.↗
NASA NTRS2023

The Temporal Brightening of Uranus’ Northern Polar Hood from HST/WFC3 & HST/STIS Observations

Hubble Space Telescope Wide-Field Camera 3 (HST/WFC3) observations spanning 2015 to 2021 confirm a brightening of Uranus' north polar hood feature with time. The vertical aerosol model of Irwin et al. (2023, https://doi.org/10.1038/s41550-023-02047-0) (IRW23), consisting of a deep haze layer based at ∼5 bar, a 1–2 bar haze layer, and an extended haze rising up from the 1–2 bar layer, was applied to retrievals on HST Space Telescope Imaging Spectrograph (STIS) (HST/STIS) observations (Sromovsky et al., 2014, 2019, https://doi.org/10.1016/j.icarus.2014.05.016, https://doi.org/10.1016/j.icarus.2018.06.026) revealing a reduction in cloud-top CH4 volume mixing ratio (VMR) (i.e., above the deep ∼5 bar haze) by an average of 0.0019 ± 0.0003 between 40–80◦N (∼10% average reduction) from 2012 to 2015. A combination of latitudinal retrievals on the HST/WFC3 and HST/STIS data sets, again employing the IRW23 model, reveal a temporal thickening of the 1–2 bar haze layer to be the main cause of the polar hood brightening, finding an average increase in integrated opacity of 1.09 ± 0.08 (∼33% increase) at 0.8 µm north of ∼45°N, concurrent with a decrease in the imaginary refractive index spectrum of the 1–2 bar haze layer north of ∼40°N and longwards of ∼0.7 µm. Small contributions to the brightening were found from a thickening of the deep aerosol layer, with an average increase in integrated opacity of 0.6 ± 0.1 (58% increase) north of 45°N between 2012 and 2015, and from the aforementioned decrease in CH4 VMR. Our results are consistent with the slowing of a stratospheric meridional circulation, exhibiting subsidence at the poles.

Arjuna James↗
NASA NTRS2015

Spectrographic Polarimeter and Method of Recording State of Polarity

A single-shot real-time spectropolarimeter for use in astronomy and other sciences that captures and encodes some or all of the Stokes polarization parameters simultaneously using only static, robust optical components with no moving parts is described. The polarization information is encoded onto the spectrograph at each wavelength along the spatial dimension of the 2D output data array. The varying embodiments of the concept include both a two-Stokes implementation (in which any two of the three Stokes polarization parameters are measured) and a full Stokes implementation (in which all three of the Stokes polarization parameters are measured), each of which is provided in either single beam or dual beam forms.

Sparks, William B.↗
NASA NTRS1997

Polar Wind in the Context of the Auroral Plasma Fountain for 2 to 8 RE

Operations of the POLAR Plasma Source Instrument have provided adequate observing time with controlled spacecraft potential to begin a 3D characterization of the polar wind as it exists in the context of the auroral plasma fountain. The principal periods of such polar wind observation to date have been 15-18 Apr. 96, 28 may 96, 14 Jun. - 6 Sep. 96, 17-29 Mar. 97, 29 May - 12 Jun. 97, 13-27 Aug. 97. Separate observations have been made near 2 RE geocentric in the south polar perigee passes and between 6-8 RE geocentric in the north polar apogee passes. Analyses of data from the Thermal Ion Dynamics Experiment during these periods are used to characterize the altitude, local time, and invariant latitude distribution of the polar wind. Data from these and other periods are used to establish the auroral plasma heating context within which the polar wind outflows exist. The available data will be used to address the temporal variability of the polar wind during the period of operations to date. Comparisons between the observations and a coupled fluid-semikinetic model are used to interpret the observed spatial structure and temporal variability.

Moore, T. E.↗
NASA NTRS1985

Comparison of polar cap potential drops estimated from solar wind and ground magnetometer data - CDAW 6

It is pointed out that the maximum electrostatic potential difference across the polar cap, Phi, is a fundamental measure of the coupling between the solar wind and the earth's magnetosphere/ionosphere sytem. During the Coordinated Data Analysis Workshop (CDAW) 6 intervals, no suitably instrumented spacecraft was in an appropriate orbit to determine the polar-cap potential drop directly. However, two recently developed independent techniques make it possible to estimate the polar-cap potential drop for times when direct spacecraft data are not available. The present investigation is concerned with a comparison of cross-polar-cap potential drop estimates calculated for the two CDAW 6 intervals on the basis of these two techniques. In the case of one interval, the agreement between the potential drops and Joule heating rates is relatively good. In the second interval, however, the agreement is not very good. Explanations for this discrepancy are discussed.

Reiff, P. H.↗
NASA NTRS1986

Optical image subtraction techniques, 1975-1985

Real- and nonreal-time optical image subtraction (OIS) techniques are reviewed. Real-time OIS techniques include source encoding, polarization modulation, pseudocolor image difference detection, the holographic shear lens technique, and nonlinear optics. Included in the nonreal-time category are speckle diffuser encoding, speckle-pattern encoding, halftone screen encoding, and polarization-shifted encoding. It is concluded that the most useful techniques are the real-time operations. It is noted that some nonreal-time optical techniques can be applied directly while others may be converted into real-time ones through the use of advance real-time spatial light modulators or electrooptic devices.

Liu, Hua-Kuang↗
NASA NTRS2018

The Advanced Energetic Pair Telescope for Gamma-Ray Polarimetry

The Advanced Energetic Pair Telescope (AdEPT), a future NASA/GSFC MIDEX mission, is being developed to perform high-sensitivity medium-energy (5-200 MeV) astronomy and revolutionary gamma-ray polarization measurements. The enabling technology for AdEPT is the Three- Dimensional Track Imager (3-DTI), a large volume gaseous time projection chamber with 2- dimentional micro-well detector (MWD) readout. The low density and high spatial resolution of the 3-DTI allows AdEPT to achieve high angular resolution (~0.5 at 67.5 MeV) and, for the first time, exceptional gamma-ray polarization sensitivity. These capabilities enable a wide range of scientific discovery potential for AdEPT. The key science goals of the AdEPT mission include: 1) Explore fundamental processes of particle acceleration in active astrophysical objects, 2) Reveal the magnetic field configuration of the most energetic accelerators in the Universe, 3) Explore the origins and acceleration of cosmic rays and the Galactic MeV diffuse emission, 4) Search for dark matter in the Galactic center, and 5) Test relativity with polarization measurements. We report on the latest developments of the MWDs for the 3-DTI.

Hunter, Stanley D.↗
NASA NTRS1992

The interannual variability of polar cap recessions as a measure of Martian climate and weather: Using Earth-based data to augment the time line for the Mars observer mapping mission

The recessions of the polar ice caps are the most visible and most studied indication of seasonal change on Mars. Circumstantial evidence links these recessions to the seasonal cycles of CO2, water, and dust. The possible advent of a planet encircling storm during the Mars Observer (MO) mission will provide a detailed correlation with a cap recession for that one Martian year. That cap recession will then be compared with other storm and nonstorm years. MO data will also provide a stronger link between cap recessions and the water and CO2 cycles. Cap recession variability might also be used to determine the variability of these cycles. After nearly a century of valiant attempts at measuring polar cap recessions, including Mariner 9 and Viking data, MO will provide the first comprehensive dataset. In contrast to MO, the older data are much less detailed and precise and could be forgotten, except that it will still be the only information on interannual variability. By obtaining simultaneous Earth-based observations (including those from Hubble) during the MO mission, direct comparisons can be made between the datasets.

Martin, L. J.↗
NASA NTRS1973

A Geopause satellite system concept.

The Geopause satellite system concept offers promising approaches in connection with four different problem areas. A typical Geopause satellite orbit has a 14-hour period, a mean height of about 4.6 earth radii, and is nearly circular, polar, and normal to the ecliptic. At this height only a relatively few gravity terms have uncertainties corresponding to orbital perturbations above the decimeter level. The Geopause satellite system also provides the tracking geometery and coverage needed for determining the orbit, the tracking system biases, and the station locations. Studies indicate that the Geopause satellite, tracked with a 2-cm ranging system from nine NASA affiliated sites, can yield decimeter station location accuracies. Five or more fundamental stations well distributed in longitude can view Geopause over the North Pole. This means not only that redundant data are available for determining tracking system biases, but also that both components of the polar motion can be observed frequently. When tracking Geopause, the NASA sites become a two-hemisphere configuration which is ideal for a number of earth physics applications such as the observation of the polar motion with a time resolution of a fraction of a day.

Siry, J. W.↗
NASA NTRS1973

Apollo/Saturn 5 Postflight Trajectory - SA-513 Skylab 1 Mission. Tracking and Flight Reconstruction

The postflight trajectory for the Apollo/Saturn V SA-513 Skylab I flight is presented. An analysis is included of the orbital and powered flight trajectories of the launch vehicle, the orbital trajectory of the spent S-II stage, and the free flight impact trajectory of the expended S-IC stage. Launch vehicle trajectory dependent parameters are provided in earth-fixed launch site, launch vehicle navigation, and geographic polar coordinate systems. The time history of the trajectory parameters for the launch vehicle is presented from guidance reference release to the transfer to ATM control. Tables of significant launch vehicle parameters at engine cutoff, stage separation, and workshop orbit insertion are included. Figures of such parameters as altitude, surface and cross range, and the magnitude of total velocity and acceleration as a function of range time for the powered flight trajectory are given.

Source record↗
NASA NTRS1973

Apollo/Saturn 5 postflight trajectory: AS-512

The postflight trajectory is presented for the Apollo/Saturn V AS-512 flight. An analysis is included of the orbital and powered flight trajectories of the launch vehicle and the free flight trajectories of the expended S-IC and S-II stages. Trajectory dependent parameters are provided in earth-fixed launch site, launch vehicle navigation, and geographic polar coordinate systems. The time history of the trajectory parameters for the launch vehicle is presented from guidance reference release to Command Service Module (CSM) separation. Tables of significant parameters at engine cutoff, stage separation, parking orbit insertion, and translunar injection are included. Figures of such parameters as altitude, surface and cross range, and the magnitude of total velocity and acceleration as a function of range time for the powered flight trajectories are presented.

Pinson, G. T.↗