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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 415 records · Page 23
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NASA NTRS1974

Skylab II - Seeing the sun in a different light

The second Skylab mission continued the detailed investigation of man's interrelated physiological functions as they react to the novel situation of weightlessness in orbit. In general terms, the most important finding is that the increase in mission duration from 28 to 59 days failed to reveal any effects that would put a specific upper limit on the time that men can live in weightlessness. Observations of the sun during the second mission covered almost two full solar revolutions, yielding detailed data on the evolution of several active regions as they traversed the face of the sun, disappeared around the limb, then reappeared on the next cycle.

Green, W. D.↗
NASA NTRS2009

An Intelligent Archive Testbed Incorporating Data Mining

Many significant advances have occurred during the last two decades in remote sensing instrumentation, computation, storage, and communication technology. A series of Earth observing satellites have been launched by U.S. and international agencies and have been operating and collecting global data on a regular basis. These advances have created a data rich environment for scientific research and applications. NASA s Earth Observing System (EOS) Data and Information System (EOSDIS) has been operational since August 1994 with support for pre-EOS data. Currently, EOSDIS supports all the EOS missions including Terra (1999), Aqua (2002), ICESat (2002) and Aura (2004). EOSDIS has been effectively capturing, processing and archiving several terabytes of standard data products each day. It has also been distributing these data products at a rate of several terabytes per day to a diverse and globally distributed user community (Ramapriyan et al. 2009). There are other NASA-sponsored data system activities including measurement-based systems such as the Ocean Data Processing System and the Precipitation Processing system, and several projects under the Research, Education and Applications Solutions Network (REASoN), Making Earth Science Data Records for Use in Research Environments (MEaSUREs), and the Advancing Collaborative Connections for Earth-Sun System Science (ACCESS) programs. Together, these activities provide a rich set of resources constituting a value chain for users to obtain data at various levels ranging from raw radiances to interdisciplinary model outputs. The result has been a significant leap in our understanding of the Earth systems that all humans depend on for their enjoyment, livelihood, and survival. The trend in the community today is towards many distributed sets of providers of data and services. Despite this, visions for the future include users being able to locate, fuse and utilize data with location transparency and high degree of interoperability, and being able to convert data to information and usable knowledge in an efficient, convenient manner, aided significantly by automation (Ramapriyan et al. 2004; NASA 2005). We can look upon the distributed provider environment with capabilities to convert data to information and to knowledge as an Intelligent Archive in the Context of a Knowledge Building system (IA-KBS). Some of the key capabilities of an IA-KBS are: Virtual Product Generation, Significant Event Detection, Automated Data Quality Assessment, Large-Scale Data Mining, Dynamic Feedback Loop, and Data Discovery and Efficient Requesting (Ramapriyan et al. 2004).

Ramapriyan, H.↗
NASA NTRS2011

SCOSTEP: Understanding the Climate and Weather of the Sun-Earth System

The international solar-terrestrial physics community had recognized the importance of space weather more than a decade ago, which resulted in a number of international collaborative activities such as the Climate and Weather of the Sun Earth System (CAWSES) by the Scientific Committee on Solar Terrestrial Physics (SCOSTEP). The CAWSES program is the current major scientific program of SCOSTEP that will continue until the end of the year 2013. The CAWSES program has brought scientists from all over the world together to tackle the scientific issues behind the Sun-Earth connected system and explore ways of helping the human society. In addition to the vast array of space instruments, ground based instruments have been deployed, which not only filled voids in data coverage, but also inducted young scientists from developing countries into the scientific community. This paper presents a summary of CAWSES and other SCOSTEP activities that promote space weather science via complementary approaches in international scientific collaborations, capacity building, and public outreach.

Gopalswamy, Natchimuthuk↗
NASA NTRS1993

Solar magnetic cycle

Using NSO/KP magnetograms, the pattern and rate of the emergence of magnetic flux and the development of the large-scale patterns of unipolar fields are considered in terms of the solar magnetic cycle. Magnetic flux emerges in active regions at an average rate of 2 x 10(exp 21) Mx/day, approximately 10 times the estimated rate in ephemeral regions. Observations are presented that demonstrate that the large-scale unipolar fields originate in active regions and activity nests. For cycle 21, the net contribution of ephemeral regions to the axial dipole moment of the Sun is positive, and is of opposite sign to that of active regions. Its amplitude is smaller by a factor of 6, assuming an average lifetime of ephemeral regions of 8 hours. Active regions larger than 4500 Mm(sup 2) are the primary contributor to the cycle variation of Sun's axial dipole moment.

Harvey, Karen L.↗
NASA NTRS2017

In-Flight Guidance, Navigation, and Control Performance Results for the GOES-16 Spacecraft

The Geostationary Operational Environmental Satellite-R Series (GOES-R), which launched in November 2016, is the first of the next generation geostationary weather satellites. GOES-R provides 4 times the resolution, 5 times the observation rate, and 3 times the number of spectral bands for Earth observations compared with its predecessor spacecraft. Additionally, Earth relative and Sun-relative pointing and pointing stability requirements are maintained throughout reaction wheel desaturation events and station keeping activities, allowing GOES-R to provide continuous Earth and sun observations. This paper reviews the pointing control, pointing stability, attitude knowledge, and orbit knowledge requirements necessary to realize the ambitious Image Navigation and Registration (INR) objectives of GOES-R. This paper presents a comparison between low-frequency on-orbit pointing results and simulation predictions for both the Earth Pointed Platform (EPP) and Sun Pointed Platform (SPP). Results indicate excellent agreement between simulation predictions and observed on-orbit performance, and compliance with pointing performance requirements. The EPP instrument suite includes 6 seismic accelerometers sampled at 2 KHz, allowing in-flight verification of jitter responses and comparison back to simulation predictions. This paper presents flight results of acceleration, shock response spectrum (SRS), and instrument line of sight responses for various operational scenarios and instrument observation modes. The results demonstrate the effectiveness of the dual-isolation approach employed on GOES-R. The spacecraft provides attitude and rate data to the primary Earth-observing instrument at 100 Hz, which are used to adjust instrument scanning. The data must meet accuracy and latency numbers defined by the Integrated Rate Error (IRE) requirements. This paper discusses the on-orbit IRE results, showing compliance to these requirements with margin. During the spacecraft checkout period, IRE disturbances were observed and subsequently attributed to thermal control of the Inertial Measurement Unit (IMU) mounting interface. Adjustments of IMU thermal control and the resulting improvements in IRE are presented. Orbit knowledge represents the final element of INR performance. Extremely accurate orbital position is achieved by GPS navigation at Geosynchronous Earth Orbit (GEO). On-orbit performance results are shown demonstrating compliance with the stringent orbit position accuracy requirements of GOES-R, including during station keeping activities and momentum desaturation events. As we show in this paper, the on-orbit performance of the GNC design provides the necessary capabilities to achieve GOES-R mission objectives.

Chapel, Jim↗
NASA NTRS1978

Using dynamo theory to predict the sunspot number during solar cycle 21

On physical grounds it is suggested that the polar field strength of the sun near a solar minimum is closely related to the solar activity of the following cycle. Four methods of estimating the polar magnetic field strength of the sun near solar minimum are employed to provide an estimate of the yearly mean sunspot number of cycle 21 at solar maximum of 140 + or - 20. This estimate may be considered a first-order attempt to predict the cycle activity using one parameter of physical importance based upon dynamo theory.

Schatten, K. H.↗
NASA NTRS1987

Solar activity, magnetic clouds, and geomagnetic storms

Associational aspects of magnetic clouds and solar activity, and of magnetic clouds and geomagentic storms are described. For example, recent research has shown associations to exist between the launch of magnetic clouds directed Earthward from the Sun and, in particular, two forms of solar activity: flare-related, type II metric radio bursts and disappearing filaments (prominences). Furthermore, recent research has shown an association to exist between the onset of magnetic clouds on Earth and the initiation of geomagnetic storms. Based on these findings, STIP Intervals XV-XIX are examined for possible occurrences of Earthward-directed magnetic clouds.

Wilson, Robert M.↗
NASA NTRS2002

A Solar Model with g-Modes

Good evidence is assembled showing that the Suit's core arid surface vary on time scales from a month to a decade arid that a number of scales are similar. The most plausible source for numerous long time scales and periodicities is long-lived global oscillations. This suggests g-modes (oscillations restored mainly by buoyancy) because they particularly affect the core and base of the convective envelope, which then indirectly modulates the surface. Also, standing g-modes have rotational properties that match many observed periodicities. But the standard solar model (SSM) has a static core and excites few if any g-modes. making new interior structures worth exploring. The model outlined here assumes two well mixed shells near 0.18 and 0.68 R, (13 = solar radius) where sound speed data shows sharp deviations from the SSM. Mixing is sustained by flows driven by the oscillations. The shells form a cavity that excludes g-modes from their main damping region below 0.1 R, assisting their net excitation and increasing their oscillation periods by at least a factor of two and probably much more. In terms of the solar luminosity L, the modes transport up through the cavity a power approx. 0.004 L as a lower limit and 0.11 L as all upper limit. The modes dissipate energy in the outer shell and cool the inner shell, asymmetrically in each case, and this stimulates occasional convective events whose response time is typically 0.8 years longer near the inner shell. Such events cool the core and reduce neutrino flux while heating the envelope and increasing solar activity. This gives a physical basis for a well mixed Sun with low neutrino flux and basis for the observed anticorrelation and lag of neutrino behind surface activity.

Wolff, Charles L.↗
NASA NTRS1984

Progress in the study of homologous flares on the sun. II

Studies of groups of homologous flares in active regions in 1980 were performed using a variety of space and ground-based instruments. The properties of three of the groups are described and combined to form a possible sequence of events.

Woodgate, B. E.↗
NASA NTRS1992

Very Large Array-RATAN 600 observations of a solar active region

VLA-RATAN-600 observations of the sun around the partial solar eclipse in July 1990 are discussed. The relatively flat spectrum of the extended emission is attributed to the optically thin thermal bremsstrahlung of electrons trapped in a magnetic loop at coronal temperatures. Step-spectrum sunspot-associated emission is attributed to thermal gyroresonance radiation at different heights along the leg of a loop joining regions of positive magnetic polarity. Comparisons with predicted distributions of gyroresonance radio indicate that compact sunspot-associated sources lie at heights of 2500-17,500 km above the photosphere. Differences in the observed and predicted microwave emission suggest an inhomogeneous distribution of thermal plasma in the corona above the sunspot or the presence of localized flux tubes containing higher density plasma or nonpotential fields.

Bogod, V. M.↗
NASA NTRS1976

A possible variation of the solar rotation with the activity cycle

Daily spectroscopic observation of the rotation of the sun indicates that several slow changes have taken place since 1967. The equatorial rotation rate of the photospheric gas has gradually increased until, in 1976, it is close to the sunspot rate determined by Newton and Nunn (1951). The latitude gradient at middle latitudes decreased starting in 1974, and the latitude gradient at high latitudes has increased in the same interval. An increase in the number of low-latitude active regions may be responsible for accelerating the photospheric gas.

Howard, R.↗
NASA NTRSDate not supplied

Lunar TLP's and the Tectonic Processes of the Earth and the Moon

We study the transient lunar phenomena (TLP) as an indicator of lunar tectonic. Seismic phenomena can be used as a direct indicator of some tectonic activities of the planets The Moon-Earth gravitational interaction has been studied extensively as a triggering mechanism to geodynamics. In this work, we study the reverse interaction Earth-Moon in relation to the TLP activities. The lunar outgassing potentially is the leading cause for TLP activities resulting from the lunar interior's dynamic mechanism. We have studied Earth venting and earthquakes processes and have found that radon was frequently activated before significant seismic events due to Moon-Sun interaction with Earth (Ouzounov et al., 2018). Earthquake lights, an associated phenomenon reported before some major earthquakes, are analog to TLP activities on the moon. In 1972, N. Kozyrev suggested a possible moon response to the significant seismic events on Earth. To understand whether TLP's activities have any possible connection with Earth geodynamics, we perform a statistical check between the significant seismic activities from the NEIC catalog and lunar TLPs for 1907-1977 for four lunar areas :Aristarchus, Plato, Gassendi, and Alphonsus. We use TLP compiled catalog based on Middlehurst et al. (1968), Cameron (2006a,b), and Crotts (2008) catalogs. Our results revealed a causal relationship between significant earthquakes and TLP events. However, this relation varies from the location and depth of the seismic events. Deformation triggers the degassing process, and TLPs are indicators for those underlying activities. Our work can provide new information about the origin of TLP and the existence of a possible relationship between the tectonic processes of Earth and the Moon.

D Ouzonov↗
NASA NTRS2023

A SmallSat Concept to Resolve Diurnal and Vertical Variations of Aerosols, Clouds, and Boundary Layer Height

A SmallSat mission concept is formulated here to carry out Time-varying Optical Measurements of Clouds and Aerosol Transport (TOMCAT) from space while embracing low-cost opportunities enabled by the revolution in Earth science observation technologies. TOMCAT’s “around-the-clock” measurements will provide needed insights and strong synergy with existing Earth observation satellites to 1) statistically resolve diurnal and vertical variation of cirrus cloud properties (key to Earth’s radiation budget), 2) determine the impacts of regional and seasonal planetary boundary layer (PBL) diurnal variation on surface air quality and low-level cloud distributions, and 3) characterize smoke and dust emission processes impacting their long-range transport on the subseasonal to seasonal time scales. Clouds, aerosol particles, and the PBL play critical roles in Earth’s climate system at multiple spatiotemporal scales. Yet their vertical variations as a function of local time are poorly measured from space. Active sensors for profiling the atmosphere typically utilize sun-synchronous low-Earth orbits (LEO) with rather limited temporal and spatial coverage, inhibiting the characterization of spatiotemporal variability. Pairing compact active lidar and passive multiangle remote sensing technologies from an inclined LEO platform enables measurements of the diurnal and vertical variability of aerosols, clouds, and aerosol-mixing-layer (or PBL) height in tropical-to-midlatitude regions where most of the world’s population resides. TOMCAT is conceived to bring potential societal benefits by delivering its data products in near–real time and offering on-demand hazard-monitoring capabilities to profile fire injection of smoke particles, the frontal lofting of dust particles, and the eruptive rise of volcanic plumes.

John E. Yorks↗
NASA NTRS1987

Comparison of active regions on the nucleus of Comet Halley

The images of the nucleus of Comet Halley returned by the Giotto spacecraft reveal a number of active regions on the surface, one of which is near the expected location of the rotation axis. This feature is larger and brighter than other source regions, suggesting that the mechanism which drives this source is also different. At this active region near the rotation pole the Sun is circumpolar for a significant portion of the solar encounter. Continuous solar insolation causes heating of the nucleus to greater depths and results in the unique properties of this source region. For example, the dust scattering in the antisolar regions around the nucleus is less from the polar region than from the region at the sunward end of the nucleus, consistent with spotty ejection of dusty mantle from the sunward tip and widespread activity in the polar region.

Reitsema, H. J.↗
NASA NTRS1988

SUMER: Solar Ultraviolet Measurements of Emitted Radiation

The SUMER (solar ultraviolet measurements of emitted radiation) experiment is described. It will study flows, turbulent motions, waves, temperatures and densities of the plasma in the upper atmosphere of the Sun. Structures and events associated with solar magnetic activity will be observed on various spatial and temporal scales. This will contribute to the understanding of coronal heating processes and the solar wind expansion. The instrument will take images of the Sun in EUV (extreme ultra violet) light with high resolution in space, wavelength and time. The spatial resolution and spectral resolving power of the instrument are described. Spectral shifts can be determined with subpixel accuracy. The wavelength range extends from 500 to 1600 angstroms. The integration time can be as short as one second. Line profiles, shifts and broadenings are studied. Ratios of temperature and density sensitive EUV emission lines are established.

Wilhelm, K.↗
NASA NTRS2014

ALMA Observations of α Centauri First Detection of Main-Sequence Stars at 3 mm Wavelength

The precise mechanisms that provide the non-radiative energy for heating the chromosphere and the corona of the Sun and those of other stars constitute an active field of research. By studying stellar chromospheres one aims at identifying the relevant physical processes. Defining the permittable extent of the parameter space can also serve as a template for the Sun-as-a-star. This feedback will probably also help identify stars that potentially host planetary systems that are reminiscent of our own. Earlier observations with Herschel and APEX have revealed the temperature minimum of Alpha Cen, but these were unable to spatially resolve the binary into individual components. With the data reported in this Letter, we aim at remedying this shortcoming. Furthermore, these earlier data were limited to the wavelength region between 100 and 870 um. In the present context, we intend to extend the spectral mapping (SED) to longer wavelengths, where the contrast between stellar photospheric and chromospheric emission becomes increasingly evident. The Atacama Large Millimeter submillimeter Array (ALMA) is particularly suited to point sources, such as unresolved stars. ALMA provides the means to achieve our objectives with both its high sensitivity of the collecting area for the detection of weak signals and the high spatial resolving power of its adaptable interferometer for imaging close multiple stars. This is the first detection of main-sequence stars at a wavelength of 3 mm. Furthermore, the individual components of the binary Alpha CenAB are clearly detected and spatially well resolved at all ALMA wavelengths. The high signal-to-noise ratios of these data permit accurate determination of their relative flux ratios, i.e., S(sub y(sup B)) / S(sub y(sup A))> = 0.54 +/- 0.04 at 440 μm, = 0.46 +/- 0.01 at 870 μm, and = 0.47 +/- 0.006 at 3.1 mm, respectively.. The previously obtained flux ratio of 0.44+/-0.18, which was based on measurements in the optical and at 70 μm, is consistent with the present ALMA results, albeit with a large error bar. The observed 3.1 mm emission greatly exceeds what is predicted from the stellar photospheres, and undoubtedly arises predominantly as free-free emission in the ionized chromospheric plasmas of both stars. Given the distinct difference in their cyclic activity, the similarity of their submm SEDs appears surprising.

Herschel↗
NASA NTRS2014

Hi-C Observations of an Active Region Corona, and Investigation of the Underlying Magnetic Structure

The solar corona is much hotter (>=10(exp 6) K) than its surface (approx 6000 K), puzzling astrophysicists for several decades. Active region (AR) corona is again hotter than the quiet Sun (QS) corona by a factor of 4-10. The most widely accepted mechanism that could heat the active region corona is the energy release by current dissipation via reconnection of braided magnetic field structure, first proposed by E. N. Parker three decades ago. The first observational evidence for this mechanism has only recently been presented by Cirtain et al. by using High-resolution Coronal Imager (Hi-C) observations of an AR corona at a spatial resolution of 0.2 arcsec, which is required to resolve the coronal loops, and was not available before the rocket flight of Hi-C in July 2012. The Hi-C project is led by NASA/MSFC. In the case of the QS, work done by convection/granulation on the inter-granular feet of the coronal field lines translates into the heat observed in the corona. In the case of the AR, as here, there could be flux emergence, cancellation/submergence, or shear flows generating large stress and tension in coronal field loops which is released as heat in the corona. We are currently investigating the changes taking place in photospheric feet of the magnetic field involved with brightenings in the Hi-C AR corona. For this purpose, we are also using SDO/AIA data of +/- 2 hours around the 5 minutes Hi-C flight. In the present talk, I will first summarize some of the results of the Hi-C observations and then present some results from our recent analysis on what photospheric processes feed the magnetic energy that dissipates into heat in coronal loops.

Tiwari, S. K.↗
NASA NTRS1989

Solar or meteorological control of lower ionospheric fluctuations (2-15 and 27 days) in middle latitudes

Several types of short and long term effects of solar activity on the lower ionosphere are related to solar flares, the sector structure of the interplanetary magnetic field and some periodicities in sunspots or solar radio flux. The most evident periodicities of the Sun are the 11 year cycle of its activity and the differential rotation period near 27 days (25 to 30 days). Here, the following questions are discussed: which periods between 2 and 15 days and near 27 days occur in ionospheric absorption during the interval July 1980 to July 1985 and are these periods related to similar periods in solar Ly-alpha flux, geomagnetic activity, or neutral wind near 95 km observed in Collm (GDR). Day-time absorption data obtained by the A3 method was used for the following radio-paths: (164 kHz), (1539 kHz), (6090 kHz). With the use of these data the electron density variations in the lower ionosphere can be analyzed. An attempt was made to clarify the nature of the observed fluctuations in absorption.

Pancheva, D.↗