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All sourcesNASA NTRSDOE OSTI
NASA NTRS2006

Kilometric Continuum Radiation

Kilometric continuum (KC) is the high frequency component (approximately 100 kHz to approximately 800 kHz) of nonthermal continuum (NTC). Unlike the lower frequency portion of NTC (approximately 5 kHz to approximately 100 kHz) whose source is around the dawn sector, the source of KC occurs at all magnetic local times. The latitudinal beaming of KC as observed by GEOTAIL is, for most events, restricted to plus or minus 15 degrees magnetic latitude. KC has been observed during periods of both low and strong geomagnetic activity, with no significant correlation of wave intensity with K(sub p), index. However statistically the maximum observed frequency of KC emission tends to increase with K(sub p) index, the effect is more pronounced around solar maximum, but is also detected near solar minimum. There is strong evidence that the source region of KC is from the equatorial plasmapause during periods when a portion of the plasmapause moves significantly inwards from its nominal position. Case studies have shown that KC emissions are nearly always associated with plasmaspheric notches, shoulders, and tails. There is a recent focus on trying to understand the banded frequency structure of this emission and its relationship to plasmaspheric density ducts and irregularities in the source region.

Green, James L.↗
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 NTRS1998

Minimum High Fire Temperatures Detected in AVIRIS Spectral Measurements from Brazil in 1995

In August and September of 1995 the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) was deployed to Brazil as part of the NASA Smoke Cloud Aerosol and Radiation experiment in Brazil (SCAR-B). AVIRIS measures spectra from 400 to 2500 nm at 10-nm intervals. These spectra are acquired as images with dimensions of 11 by up to 800 km with 20-m spatial resolution. Spectral images measured by AVIRIS are spectrally, radiometrically, and spatially calibrated. During the SCAR-B deployment, AVIRIS measured more than 300 million spectra of regions of Brazil. A portion of these spectra were acquired over areas of actively burning fires. Actively burning fires emit radiance in the AVIRIS spectral range as a function of temperature. This emitted radiance is expressed from the 2500-nm end of the AVIRIS spectrum to shorter wavelengths as a function of intensity and modeled by the Planck function. The objective of this research and analysis was to use spectroscopic methods to determine the minimum high temperature of the most intense fires measured in the SCAR-B AVIRIS data set. Spectra measured by AVIRIS with hot sources have been previously examined for volcanic lava.

Green, Robert O.↗
NASA NTRS1998

Minimum High Fire Temperatures Detected in AVIRIS Spectral Measurements from Brazil in 1995

In August and September of 1995 the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) was deployed to Brazil as part of the NASA Smoke Cloud Aerosol and Radiation experiment in Brazil (SCAR-B). AVIRIS measures spectra from 400 to 2500 nm at 10-nm intervals. These spectra are acquired as images with dimensions of 11 by up to 800 km with 20-m spatial resolution. Spectral images measured by AVIRIS are spectrally, radiometrically, and spatially calibrated. During the SCAR-B deployment, AVIRIS measured more than 300 million spectra of regions of Brazil. A portion of these spectra were acquired over areas of actively burning fires. Actively burning fires emit radiance in the AVIRIS spectral range as a function of temperature. This emitted radiance is expressed from the 2500-nm end of the AVIRIS spectrum to shorter wavelengths as a function of intensity and modeled by the Planck function.. The objective of this research and analysis was to use spectroscopic methods to determine the minimum high temperature of the most intense fires measured in the SCAR-B AVIRIS data set. Spectra measured by AVIRIS with hot sources have been previously examined for volcanic lava and fires in Brazil.

Green, Robert O.↗
NASA NTRS1984

Particle excitation, airglow and H2 vibrational disequilibrium in the atmosphere of Jupiter

The extreme ultraviolet EUV emission produced by particle excitation of the hydrogen atmospheres of Jupiter and Saturn is examined using model calculations to determine the nature of the energy deposition process and the effect of such processes on atmospheric structure. Tasks ranging from examination of phenomenologically related processes on Saturn and Titan to analysis of experimental laboratory data required to allow accurate modeling of emissions from hydrogenic atmospheres are investigated. An explanation of the hydrogen H Ly(alpha) bulge in Jupiter's emission from the equatorial region is presented. It is proposed that Saturn, rather then Titan is the major source of the extended hydrogen cloud. The atomic hydrogen detected at the rings of Saturn may originate predominantly from the same source. A cross calibration is obtained between the Pioneer 10 EUV photometer and the Voyager EUV spectrometers, thus providing a direct measure of the temporal morphology of Jupiter between a minimum and a maximum in solar activity. Atomic and molecular data required for the research program are analyzed. An extrapolation of conditions in the upper atmospheres of Jupiter and Saturn produces a predicted condition at Uranus in terms of excitation and hydrogen escape rates that may be observed at Voyager-Uranus encounter.

Shemansky, D. E.↗
NASA NTRS1994

Search for effects of Comet S-L 9 fragment impacts on low radio frequency emission from Jupiter

Decametric radio observations of Jupiter were made before, during, and after the impacts of the fragments of the comet S-L 9 with the planet, from the University of Florida Radio Observatory, the Maipu Radio Astronomy Observatory of the University of Chile, and the Owens Valley Radio Observatory of the California Institute of Technology. The decametric radiation was monitored at frequencies from 16.7 to 32 MHz. The minimum detectable flux densities were on the order of 30 kJy, except for that of the large 26.3 MHz array in Florida, which was about 1 kJy. There was no significant enhancement or suppression of the decametric L-burst or S-burst emission with respect to normal activity patterns that might be attributed to the fragment entries. A burst of left-hand elliptically polarized radiation having a considerably longer duration than an L-burst was observed almost simultaneously with the impact of the large fragment Q2, and another with right-hand elliptical polarization was observed simultaneously with Q1. We consider the possibility that these two bursts were emitted just above the local electron cyclotron frequencies from the southern and northern ends, respectively, of magnetic flux tubes that had been excited in some way by the proximity of fragments Q2 and Q1. A search was conducted for possible comet-enhanced Jovian synchrotron radiation at 45 MHz using a large dipole antenna array at the observatory in Chile.

Carr, T. D.↗
NASA NTRS2017

Modeling and Simulation Plans in Support of Low Cost, Size, Weight, and Power Surveillance Systems for Detecting and Tracking Non-Cooperative Aircraft

RTCA Special Committee (SC) 228 has initiated a second phase for the development of minimum operational performance standards (MOPS) for UAS detect and avoid (DAA) systems. Technologies to enable UAS with less available Size, Weight, and Power (SWaP) will be considered. RTCA SC-228 has established sub-working groups and one of the sub-working groups is focused on aligning modeling and simulations activities across all participating committee members. This briefing will describe NASAs modeling and simulation plans for the development of performance standards for low cost, size, weight, and power (C-SWaP) surveillance systems that detect and track non-cooperative aircraft. The briefing will also describe the simulation platform NASA intends to use to support end-to-end verification and validation for these DAA systems. Lastly, the briefing will highlight the experiment plan for our first simulation study, and provide a high-level description of our future flight test plans. This briefing does not contain any results or data.

surveillance↗
NASA NTRS2024

The CARMENES Search for Exoplanets Around M Dwarfs: Revisiting the GJ 581 Multi-Planetary System With New Doppler Measurements From CARMENES, HARPS, and HIRES

Context.GJ 581 is a nearby M dwarf known to host a packed multiple planet system composed of two super-Earths and a Neptune-mass planet. We present new orbital analyses of the GJ 581 system, utilizing recent radial velocity (RV) data obtained from the CARMENES spectrograph combined with newly reprocessed archival data from the HARPS and HIRES spectrographs. Aims.Our aim was to analyze the post-discovery spectroscopic data of GJ 581, which were obtained with CARMENES. In addition, we used publicly available HIRES and HARPS spectroscopic data to seek evidence of the known and disputed exoplanets in this system. We aimed to investigate the stellar activity of GJ 581 and update the planetary system’s orbital parameters using state-of-the-art numerical models and techniques. Methods.We performed a periodogram analysis of the available precise CARMENES, HIRES, and HARPS RVs and of stellar activity indicators. We conducted detailed orbital analyses by testing various orbital configurations consistent with the RV data. We studied the posterior probability distribution of the parameters fit to the data and we explored the long-term stability and overall orbital dynamics of the GJ 581 system. Results. We refined the orbital parameters of the GJ 581 system using the most precise and complete set of Doppler data available. Consistent with the existing literature, our analysis confirms that the system is unequivocally composed of only three planets detectable in the present data, dismissing the putative planet GJ 581 d as an artifact of stellar activity. Our N-body fit reveals that the system’s inclination is i=47.0+14.6−13.0deg, which implies that the planets could be up to 30% more massive than their previously reported minimum masses. Furthermore, we report that the GJ 581 system exhibits long-term stability, as indicated by the posterior probability distribution, characterized by secular dynamical interactions without the involvement of mean motion resonances.

Satellites↗
NASA NTRS1991

S Persei: Optical and water maser variability - 1984 to 1990

The M supergiant S Persei was monitored since 1984 optically and since 1987 for water maser emission at 22 GHz. The dozen H2O maser features show complex variations in intensity with many of the features varying independently of one another. Some of the water maser features brightened dramatically at the time of the bright optical maximum observed in 1988 August and again 10 weeks later. It is possible the increase in water maser intensity is related to the ejection of a dust shell near the time of the preceding optical minimum. The intensity variations of the maser spectrum as being produced by an asymmetric distribution of maser spots are interpreted. A double shell of maser spots may be present on the near side of the shell, but appears to be lacking or be occulted on the far side. No chromospheric activity was detected about 10 weeks after optical maximum. A well developed shock is seen in a near-infrared spectrum obtained in 1988 October.

Little-Marenin, I. R.↗
NASA NTRS2011

The High-Energy View of the Broad-Line Radio Galaxy 3C 111

We present the analysis of Suzaku and XMM -Newton observations of the broad-line radio galaxy (BLRG) 3C 111. Its high-energy emission shows variability, a harder continuum with respect to the radio-quiet active galactic nucleus population, and weak reflection features. Suzaku found the source in a minimum flux level; a comparison with the XMM-Newton data implies an increase of a factor of 2.5 in the 0.5-10 keV flux, in the 6 months separating the two observations. The iron K complex is detected in both data sets, with rather low equivalent width(s). The intensity of the iron K complex does not respond to the change in continuum flux. An ultrafast, high-ionization outflowing gas is clearly detected in the Suzaku/X-ray Imaging Spectrometer data; the absorber is most likely unstable. Indeed, during the XMM-Newton observation, which was 6 months after, the absorber was not detected. No clear rollover in the hard X-ray emission is detected, probably due to the emergence of the jet as a dominant component in the hard X-ray band, as suggested by the detection above approx.100 keV with the GSO onboard Suzaku, although the present data do not allow us to firmly constrain the relative contribution of the different components. The fluxes observed by the gamma-ray satellites CGRO and Fermi would be compatible with the putative jet component if peaking at energies E approx. 100MeV. In the X-ray band, the jet contribution to the continuum starts to be significant only above 10 keV. If the detection of the jet component in 3C 111 is confirmed, then its relative importance in the X-ray energy band could explain the different observed properties in the high-energy emission of BLRGs, which are otherwise similar in their other multiwavelength properties. Comparison between X-ray and gamma -ray data taken at different epochs suggests that the strong variability observed for 3C 111 is probably driven by a change in the primary continuum.

Ballo, L.↗
NASA NTRS1980

The morphology of metallic ions in the upper atmosphere

Analysis of metallic ion data from a day-night pair of rockets, OGO 6, and the elliptic phases of AE-C and AE-D shows the presence of Fe(+) ions at altitudes above 400 km only at low magnetic latitudes. The detection probability of this ion decreases with altitude, with a maximum over the Atlantic and a minimum over India; the rocket data indicate ions in the E region during the day and on the bottom of the F layer at night. Mg(+) and Fe(+) are the dominant ions below 250 km at all latitudes, but Al(+), Na(+), Si(+), and Ca(+) are also detectable; a correlation was found between solar activity and metallic ion detection probability at low latitudes and high altitudes at night

Kumar, S.↗
NASA NTRS1979

Portable device for detection of petit mal epilepsy

A portable device that analyzes the electroencephalogram to determine if petit mal epilepsy waveforms are present is developed and tested. Clinicians should find it useful in diagnosing seizure activity of their patients. The micropower, battery-operated, portable device indicates a seizure has occurred if three criteria are satisfied: (1) frequencies of 2.5-7 Hz, (2) large-amplitude waves, and (3) minimum number of waves per second. Levels and counts are adjustable, thus insuring high reliability against noise artifacts and permitting each subject to be individually fitted. The device has shown promise in giving the patient a possible mechanism of seizure control or suppression.

Smith, R. G.↗
NASA NTRS2014

IXPE: The Imaging X-ray Polarimetry Explorer, Implementing a Dedicated Polarimetry Mission

Only a few experiments have conducted x-ray polarimetry of cosmic sources since Weisskopf et al confirmed the 19% polarization of the Crab Nebula with the Orbiting Solar Observatory (OSO-8) in the 70's center dot The challenge is to measure a faint polarized component against a background of non-polarized signal (as well as the other, typical background components) center dot Typically, for a few % minimum detectable polarization, 106 photons are required. center dot So, a dedicated mission is vital with instruments that are designed specifically to measure polarization (with minimal systematic effects) Over the proposed mission life (2- 3 years), IXPE will first survey representative samples of several categories of targets: magnetars, isolated pulsars, pulsar wind nebula and supernova remnants, microquasars, active galaxies etc. The survey results will guide detailed follow-up observations. Precise calibration of IXPE is vital to ensuring sensitivity goals are met. The detectors will be characterized in Italy, and then a full calibration of the complete instrument will be performed at MSFC's stray light facility. Polarized flux at different energies Heritage: X-ray Optics at MSFC polarimetry mission.

Ramsey, Brian↗
NASA NTRS2006

Precision Astrometry with SIM PlanetQuest: Science and Mission Update

This viewgraph presentation gives a science and mission update of precision Astrometry with the Space Interferometry Mission (SIM) PlanetQuest. The topics include: 1) SIM PlanetQuest - the World s First Long- Baseline Optical Interferometer in Space; 2) National Academy of Sciences / NRC endorses SIM PlanetQuest; 3) Astrometry with an Interferometer; 4) Overall Configuration (deployed); 5) SIM Planet Finding Capabilities; 6) Planet detection with SIM - minimum masses; 7) Searching for Terrestrial Planets with SIM; 8) Planets around Young Stars; 9) SIM PlanetQuest Science Team; 10) SIM Astrophysics; 11) SIM's Reach Extends Across our Entire Galaxy to do Precision Astrophysics; 12) Dynamics of Galaxy Groups within 5 Mpc; 13) Galactic tidal tails; 14) Dark Halo of our Galaxy; 15) Probing Active Galactic Nuclei with Astrometry; 16) Sample tile for relative astrometry; 17) Astrometric signatures of AGN; 18) Snapshot Observing Mode: Astrometry for the masses; and 19) SIM Technology Development is Complete.

space interferometry mission (SIM)↗
NASA NTRS2004

Mesoscale Gravity Wave Variances from AMSU-A Radiances

A variance analysis technique is developed here to extract gravity wave (GW) induced temperature fluctuations from NOAA AMSU-A (Advanced Microwave Sounding Unit-A) radiance measurements. By carefully removing the instrument/measurement noise, the algorithm can produce reliable GW variances with the minimum detectable value as small as 0.1 K2. Preliminary analyses with AMSU-A data show GW variance maps in the stratosphere have very similar distributions to those found with the UARS MLS (Upper Atmosphere Research Satellite Microwave Limb Sounder). However, the AMSU-A offers better horizontal and temporal resolution for observing regional GW variability, such as activity over sub-Antarctic islands.

middle atmosphere↗
DOE OSTI2026

Performance evaluation of neutron noise analysis in detecting special nuclear materials

Reliable and rapid inspection techniques play a vital role in preventing illicit trafficking of special nuclear materials. Active interrogation systems using neutrons produced by portable, high-flux deuterium-deuterium or deuterium-tritium neutron generators are being actively developed as a secondary scanning tool for this purpose. In this study, a neutron noise analysis-based approach for detecting unshielded and shielded special nuclear materials by using a pulsed deuterium-tritium neutron generator was evaluated. Here, this approach analyzes the fluctuation of neutron counts. Its performance was quantified with regard to time-to-detection to achieve a minimum probability of detection of 99% and a probability of false alarm of less than 1% considering various amounts of special nuclear materials and different shielding configurations. It was demonstrated that this approach could detect 17 uranium slugs in 5 s given a neutron generator yield of 8.1 × 10 7 n/s. These slugs could be detected within a reasonable time frame (200 s) when they were shielded by 10.16 cm of high-density polyethylene. The results obtained using the neutron noise analysis approach were compared with those obtained using the commonly used differential die-away analysis technique, a sensitive technique for detecting the presence of fissile materials by utilizing the prompt fission neutrons produced when the source neutrons from a neutron generator are completely diminished. For example, the time to detect 2 unshielded uranium slugs was 2.1 s when using the differential die-away analysis technique; it increased to 93 s for the neutron noise analysis approach. Although the noise analysis-based approach exhibits an overall performance which is not as good as that of differential die-away, neutron noise provides an alternative method for effective detection of special nuclear materials.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS2004

Solar Activity and its Impact on Earth's Climate

The Sun's activity is now approaching an expected 2006 minimum, following the dramatic maximum of Solar Cycle 23, that included events such as the 2001 "Bastille Day" Coronal Mass Ejection, and the record-setting Oct-Nov 2003 solar flares, with their associated sunspots and variations in Total Solar Irradiance, or TSI. On Nov 4,2003 the largest X-ray flare ever detected (X-28) was observed in detail. We discuss recent satellite measurements of TSI by ACRIM 2 and 3 and Virgo, and new precision observations of TSI and SSI (Solar Spectral Irradiance) from the SORCE mission, that launched on January 25,2003. TSI variations recorded during the June 8,2004 transit of Venus show the unprecedented precision of the SORCE Total Irradiance Monitor (TIM) instrument, the first of its kind to employ phase-sensitive detection. The SORCE spectral instruments, XPS, Solstice, and SIM, record the Sun's changes over a wide range of wavelengths, from 1 to more than 2000 nanometers, for the first time covering the peak of the solar spectrum, including spectral components that provide energy inputs to key components of the climate system - ultraviolet (UV) into the upper atmospheric ozone layer, infrared (IR) into the lower atmosphere and clouds, and Visible into the Oceans and biosphere. Succeeding satellite missions are planned to monitor both TSI and SSI through Cycle 24. We summarize current ideas about decadal and longer solar variability, and associated potential impacts on Earth's climate on time scales from decades to centuries, especially highlighting the role of feedbacks in the climate system.

Cahalan, Robert F.↗
NASA NTRS2016

FT4 Data Analysis Summary (SSI-ARC)

Standards for Unmanned Aircraft System (UAS) Detect-and-Avoid (DAA) systems are currently being developed under the auspices of the RTCA Special Committee 228 (SC-228). To support the development of these standards, a series of flight tests has been conducted at NASAs Armstrong Flight Research Center (NASA-AFRC). The fourth in this series of flight test activities (Flight Test 4, or simply FT4) was conducted during the Spring and Summer of 2016. FT4 supported the objectives of numerous organizations working toward UAS DAA Minimum Operational Performance Standards (MOPS) and UAS DAA Radar MOPS. The summary provided herein is limited to the objectives, analysis and conclusions of the NASA Ames Research Center (NASA-ARC) SSI team toward the refinement of UAS DAA MOPS. This document provides a high-level overview of FT4 and the SSI-ARC objectives, a summary of the data analysis methodology and recommendations for UAS DAA MOPS refinements based on the data analysis results. A total of 72 encounters were flown to support SSI-ARC objectives. Test results were generally consistent with acceptable UAS DAA system performance and will be considered in broader SC-228 requirements validation efforts. Observed alert lead times indicated acceptable UAS DAA alerting performance. Effective interoperability between the UAS DAA system and the Traffic Alert and Collision Avoidance System (TCAS) was observed with one notable exception: TCAS Resolutions Advisories (RA) were observed in the absence of any DAA alert on two occasions, indicating the need for alert parameter refinement. Findings further indicated the need for continued work in the areas of DAA Well Clear Recovery logic and alert stability for Mode-C-only intruders. Finally, results demonstrated a high level of compliance with a set of evaluation criteria designed to provide anecdotal evidence of acceptable UAS DAA system performance.

UAS Test Flight↗