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NASA NTRS2004

XTE J1550-564: INTEGRAL Observations of a Failed Outburst

The well known black-hole X-ray binary transient XTE J1550-564 underwent an outburst during the spring of 2003 which was substantially underluminous in comparison to previous periods of peak activity in that source. In addition, our analysis shows that it apparently remained in the hard spectral state over the duration of that outburst. This is again in sharp contrast to major out-bursts of that source in 1998/1999 during which it exhibited an irregular light curve, multiple state changes and collimated outflows. This leads us to classify it as a failed outburst. We present the results of our study of the spring 2003 event including light curves based on observations from both INTEGRAL and RXTE. In addition, we studied the evolution of the high-energy 3-300 keV continuum spectrum using data obtained with three main instruments on INTEGRAL. These spectra are consistent with typical low-hard-state thermal Comptonization emission. We also consider the 2003 event in the context of a multi-source, multi-event period-peak luminosity diagram in which it is a clear outlyer. We then consider the possibility that the 2003 event was due to a discrete accretion event rather than a limit-cycle instability. In that context, apply model fitting to derive the timescale for viscous propagation in the disk, and infer some physical characteristics.

Sturner, S. J.↗
NASA NTRS2005

Development of mid-IR lasers for Laser Remote Sensing

There is an existing need in JPL and in NASA for development of mid-IR lasers, such as Quantum Cascade (QC) lasers, for in-situ and remote laser spectrometers. Mid-IR, compact, low power consumption laser spectrometers have a great potential for detection and measurements of planetary gases and biological important biomarker molecules such as H20, H202, CH4, and many additional chemical species on Mars and other Solar system planets. Another potential application of QC lasers for future NASA mission is in high power remote Laser Reflectance Spectrometers (LRS). In LSR instrument, mid-infrared lasers will act as the illumination source for conducting active mid-IR reflectance spectroscopy of solid-surfaced objects in the outer Solar System. These spectrometers have the potential to provide an incredible amount of information about the compositions of surfaces in the outer Solar System. In this work, we will discuss our current effort at JPL to advance QC lasers to a level that the laser performance, operational requirements and reliability be compatible with the instruments demands for space exploration applications.

Mid - IR lasers↗
NASA NTRS2013

Mars Science Laboratory Entry, Descent, and Landing Trajectory and Atmosphere Reconstruction

On August 5th 2012, The Mars Science Laboratory entry vehicle successfully entered Mars atmosphere and landed the Curiosity rover on its surface. A Kalman filter approach has been implemented to reconstruct the entry, descent, and landing trajectory based on all available data. The data sources considered in the Kalman filtering approach include the inertial measurement unit accelerations and angular rates, the terrain descent sensor, the measured landing site, orbit determination solutions for the initial conditions, and a new set of instrumentation for planetary entry reconstruction consisting of forebody pressure sensors, known as the Mars Entry Atmospheric Data System. These pressure measurements are unique for planetary entry, descent, and landing reconstruction as they enable a reconstruction of the freestream atmospheric conditions without any prior assumptions being made on the vehicle aerodynamics. Moreover, the processing of these pressure measurements in the Kalman filter approach enables the identification of atmospheric winds, which has not been accomplished in past planetary entry reconstructions. This separation of atmosphere and aerodynamics allows for aerodynamic model reconciliation and uncertainty quantification, which directly impacts future missions. This paper describes the mathematical formulation of the Kalman filtering approach, a summary of data sources and preprocessing activities, and results of the reconstruction.

Karlgaard, Christopher D.↗
NASA NTRS2012

X-Ray and Optical Observations of A 0535+26

We present recent contemporaneous X-ray and optical observations of the Be/X-ray binary system A 0535+26 with the Fermi/Gamma-ray Burst Monitor (GBM) and several ground-based observatories. These new observations are put into the context of the rich historical data (since 1978) and discussed in terms of the neutron-star-Be-disk interaction. The Be circumstellar disk was exceptionally large just before the 2009 December giant outburst, which may explain the origin of the unusual recent X-ray activity of this source. We found a peculiar evolution of the pulse profile during this giant outburst, with the two main components evolving in opposite ways with energy. A hard 30-70 mHz X-ray quasi-periodic oscillation was detected with GBM during this 2009 December giant outburst. It becomes stronger with increasing energy and disappears at energies below 25 keV. In the long term a strong optical/X-ray correlation was found for this system, however in the medium term the Halpha equivalent width and the V-band brightness showed an anti-correlation after 2002 August. Each giant X-ray outburst occurred during a decline phase of the optical brightness, while the H showed a strong emission. In late 2010 and before the 2011 February outburst, rapid V/R variations are observed in the strength of the two peaks of the H line. These had a period of 25 days and we suggest the presence of a global one-armed oscillation to explain this scenario. A general pattern might be inferred, where the disk becomes weaker and shows V/R variability beginning 6 months following a giant outburst.

Camero-Arranz, A.↗
NASA NTRS2012

SBS 0846+513: a New Gamma-ray Emitting Narrow-line Seyfert 1 Galaxy

We report Fermi-LAT observations of the radio-loud AGN SBS 0846+513 (z=0.5835), optically classified as a Narrow-Line Seyfert 1 galaxy, together with new and archival radio-to-X-ray data. The source was not active at γ-ray energies during the first two years of Fermi operation. A significant increase in activity was observed during 2010 October-2011 August. In particular a strong gamma-ray flare was observed in 2011 June reaching an isotropic γ-ray luminosity (0.1-300 GeV) of 1.0×10(sup 48) erg s(sup −1), comparable to that of the brightest flat spectrum radio quasars, and showing spectral evolution in gamma rays. An apparent superluminal velocity of (8.2+/-1.5)c in the jet was inferred from 2011-2012 VLBA images, suggesting the presence of a highly relativistic jet. Both the power released by this object during the flaring activity and the apparent superluminal velocity are strong indications of the presence of a relativistic jet as powerful as those of blazars. In addition, variability and spectral properties in radio and gamma-ray bands indicate blazar-like behaviour, suggesting that, except for some distinct optical characteristics, SBS 0846+513 could be considered as a young blazar at the low end of the blazar's black hole mass distribution.

emitting↗
NASA NTRS2012

Atmospheric Dust Modeling from Meso to Global Scales with the Online NMMB/BSC-Dust Model Part 2: Experimental Campaigns in Northern Africa

The new NMMB/BSC-Dust model is intended to provide short to medium-range weather and dust forecasts from regional to global scales. It is an online model in which the dust aerosol dynamics and physics are solved at each model time step. The companion paper (Perez et al., 2011) develops the dust model parameterizations and provides daily to annual evaluations of the model for its global and regional configurations. Modeled aerosol optical depth (AOD) was evaluated against AERONET Sun photometers over Northern Africa, Middle East and Europe with correlations around 0.6-0.7 on average without dust data assimilation. In this paper we analyze in detail the behavior of the model using data from the Saharan Mineral dUst experiment (SAMUM-1) in 2006 and the Bodele Dust Experiment (BoDEx) in 2005. AOD from satellites and Sun photometers, vertically resolved extinction coefficients from lidars and particle size distributions at the ground and in the troposphere are used, complemented by wind profile data and surface meteorological measurements. All simulations were performed at the regional scale for the Northern African domain at the expected operational horizontal resolution of 25 km. Model results for SAMUM-1 generally show good agreement with satellite data over the most active Saharan dust sources. The model reproduces the AOD from Sun photometers close to sources and after long-range transport, and the dust size spectra at different height levels. At this resolution, the model is not able to reproduce a large haboob that occurred during the campaign. Some deficiencies are found concerning the vertical dust distribution related to the representation of the mixing height in the atmospheric part of the model. For the BoDEx episode, we found the diurnal temperature cycle to be strongly dependant on the soil moisture, which is underestimated in the NCEP analysis used for model initialization. The low level jet (LLJ) and the dust AOD over the Bodélé are well reproduced. The remaining negative AOD bias (due to underestimated surface wind speeds) can be substantially reduced by decreasing the threshold friction velocity in the model.

photometers↗
NASA NTRS2015

Radioisotope Power System Pool Concept

Advanced Radioisotope Power Systems (RPS) for NASA deep space science missions have historically used static thermoelectric-based designs because they are highly reliable, and their radioisotope heat sources can be passively cooled throughout the mission life cycle. Recently, a significant effort to develop a dynamic RPS, the Advanced Stirling Radioisotope Generator (ASRG), was conducted by NASA and the Department of Energy, because Stirling based designs offer energy conversion efficiencies four times higher than heritage thermoelectric designs; and the efficiency would proportionately reduce the amount of radioisotope fuel needed for the same power output. However, the long term reliability of a Stirling based design is a concern compared to thermoelectric designs, because for certain Stirling system architectures the radioisotope heat sources must be actively cooled via the dynamic operation of Stirling converters throughout the mission life cycle. To address this reliability concern, a new dynamic Stirling cycle RPS architecture is proposed called the RPS Pool Concept.

Power↗
NASA NTRS2016

Characterization of Potential Springs in the Lower Colorado Desert of Southern California using Satellite Radar and Landsat Time Series Analysis

Renewable energy development in southern California is receiving increasing attention due to potential impacts on wildlife habitats and water sources. This study was designed to quantify and map, for the first time, sub-surface water sources from springs in the Lower Colorado Desert area of southern California using satellite radar data and 30 years of Landsat satellite image data. Synthetic Aperture Radar (SAR) data was used to identify sub-surface water sources not already documented as springs or seeps in the National Hydrography Database. Landsat imagery starting in 1985 was used to characterize vegetation growth patterns at these suspected spring locations detected from SAR analysis. Results showed a total of 104 potential spring locations across the Lower Colorado Desert study area, 19 of which were detected within Solar Energy Zone (SEZ) development boundaries, roughly evenly split between Riverside East and Imperial East, and 13 of which (both inside and outside SEZs) showed relatively high green vegetation index values over the period of 1985 to 2015 that would depend on non-precipitation water sources associated with active springs.

DRECP↗
NASA NTRS1997

Multiwavelength Observations of a Dramatic High Energy Flare in the Blazar 3C 279

Multiwavelength observation of blazars in conjuction with EGRET points have been obtained at several epochs. However, either the monitoring was to sparse or the source was not active during the campaign, so that detections of correlated mulitwavelentgh variabiltiy on short times scales are tentaive (3C 279, Maraschi et al. 1994; Hartman et al. 1996; OJ 287, Webb et al. 1996; PKS 0537-441, Pian et al. 1997).

gamma↗
NASA NTRS2013

USNO Analysis Center for Source Structure Report

This report summarizes the activities of the United States Naval Observatory Analysis Center for Source Structure for the 2012 calendar year and the activities planned for the year 2013.

Fey, Alan L.↗
NASA NTRS1991

Active vibration isolation using smart structures

Passive technologies for the isolation of structures from vibrating sources are often inadequate. Using active control inputs applied directly to the source or designing a structure integrating the transducers required for the control inputs and the response measurements are ways of dealing with the problem. Results are given which were obtained on an experimental set up simulating this kind of problem where the form and the position of the transducers could be varied. By measuring the response of the structure integrated over a particular area the effects of particular types of modes could be taken into account to deal with specific types of input or limit particular modes of response more efficiently. Results of using different modes of vibration excitation of the receiving structure with and without control are presented for particular input frequencies. The problems of optimizing the control system to deal with multiple frequency inputs are discussed.

Guigou, C.↗
NASA NTRS1986

Dust-gas interaction deduced from Halley multicolor camera observations

The dust and gas productions of comet Halley were measured by the dust counter and the mass spectrometers on the Giotto spacecraft. These instruments give only little information about the spatial asymmetry of the activity. The asymmetry in the dust production is clearly evident from the dust jets seen in the Halley Multicolor Camera images. Since the dust is entrained by the gas, gas production must be similarly asymmetric. The intensity profiles along and across several dust jets are related to their source regions on the nucleus. Properties of the dust jets are investigated. A few compact, but highly active source regions on the nucleus produce most of the visible dust and can account for most of the gas produced by the comet.

Huebner, W. F.↗
NASA NTRS1994

X-ray and gamma-ray emission of Sagittarius A* as a wind-accreting black hole

If, as many believe, Sgr A* is a massive black hole at the Galactic center, one should expect it to be a source of X-ray and gamma-ray activity, behaving basically as a scaled-down active galactic nucleus. An unavoidable source of accretion is the wind from IRS 16, a nearby group of hot, massive stars. Since the density and velocity of the accreting matter are known from observations, the accretion rate is basically a function of the putative black hole mass, M(sub h), only; this value represents a reliable lower limit to a real rate, given the other possible sources of accreting matter. Based on this and on the theories about shock acceleration in active galactic nuclei, we have estimated the expected production of relativistic particles and their hard radiation. These values turn out to be a function of M(sub h) as well. Comparing our results with available X-ray and gamma-ray observations which show Sgr A* to have a relatively low activity level, we conclude tentatively that the putative black hole in the Galactic center cannot have a mass greater than approximately 6 x 10(exp 3) solar mass. This conclusion is consistent with the upper limits to the black hole mass found by different methods earlier, although much more work is needed to make calculations of shock acceleration around black holes more reliable.

Mastichiadis, A.↗
NASA NTRS1998

Remote Sensing of Tropospheric Aerosols from Space: Past, Present, and Future

Aerosol particles originate from man-made sources such as urban/industrial activities,rurning associated with land use processes, wind-blown dust, and natural sources. Their interaction with sunlight and their effect on cloud microphysics forms a major uncertainty in predicting climate change. Furthermore, the lifetime of only a few days causes high spatial variability in aerosol optical and radiative properties that requires global observations from space. Remote sensing of aerosol properties from space is reviewed both for present and planned national and international satellite sensors. Techniques that are being used to enhance our ability to characterize the global distribution of aerosol properties include well-calibrated multispectral radiometers, multispectral polarimeters, and multi-angle spectroradiometers. Though most of these sensor systems rely primarily on visible to mid-infrared spectral channels, the availability of of thermal channels to aid in cloud screening is an important additional piece of information that is not always incorporated into the sensor design. In this paper we describe the various satellite sensor systems being developed by Europe, Japan, and the U.S., and highlight the advantages and disadvantages of each of these systems for aerosol applications. An important underlying theme is that the remote sensing of aerosol properties, especially aerosol size distribution and single scattering albedo, is exceedingly difficult. As a consequence, no one sensor system is capable of providing totally unambiguous information, and hence a careful intercomparison of derived products from different sensors, together with a comprehensive network of ground-based sun-photometer and sky radiometer systems, are required to advance our quantitative understanding of global aerosol characteristics.

King, Michael D.↗
NASA NTRS2001

Determining the amount of physical activity needed for long-term weight control

OBJECTIVE: To evaluate prospectively the influence of habitual physical activity on body weight of men and women and to develop a model that defines the role of physical activity on longitudinal weight change. DESIGN AND SETTING: Occupational cohort study conducted for a mean of 5.5 y. SUBJECTS: A total of 496 (341 male and 155 female) NASA/Johnson Space Center employees who completed the 3 month education component of the employee health-related fitness program and remained involved for a minimum of 2 y. MEASUREMENTS: Body weights were measured at baseline (T1) and follow-up (T2), and habitual physical activity was obtained from the mean of multiple ratings of the 11-point (0-10) NASA Activity Scale (NAS) recorded quarterly between T1 and T2. Other measures included age, gender, VO(2 max) obtained from maximal treadmill testing, body mass index (BMI), and body fat percentage. RESULTS: Multiple regression demonstrated that mean NAS, T1 weight, aging and gender all influence long-term T2 weight. T1 age was significant for the men only. Independently, each increase in mean NAS significantly (P<0.01) reduced T2 weight in men (b=-0.91 kg; 95% CI:-1.4 to-0.42 kg) and women (b=-2.14 kg; 95% CI:-2.93 to-1.35 kg). Mean NAS had a greater effect on T2 weight as T1 weight increased, and the relationship was dose-dependent. CONCLUSIONS: Habitual physical activity is a significant source of long-term weight change. The use of self-reported activity level is helpful in predicting long-term weight changes and may be used by health care professionals when counseling patients about the value of physical activity for weight control.

Exercise↗
NASA NTRS2015

The Application of New Optical Meteor Flux Routines to the 2014 May Camelopardalid Outburst

NASA's Meteoroid Environment Office (MEO) is charged with monitoring the meteoroid environment in near-Earth space for the protection of satellites and spacecraft. The MEO has recently established eight wide-field meteor cameras, four cameras each at two separate stations to calculate automated meteor fluxes in the millimeter size range. Each camera consists of a 17 mm focal length Schneider lens on a Watec 902H2 Ultimate CCD video camera, producing a 21.7 x 15.5 degree field of view. This configuration has a limiting meteor magnitude of about +5. One station is located at Marshall Space Flight Center in Huntsville, Alabama and the other is 31.8 kilometers away at a school in Decatur, Alabama. Both single-station and double-station fluxes are calculated every morning using data from the previous night. The flux algorithms employed here differ from others currently in use in that they do not assume a single height for all meteors observed in the common camera volume. In the MEO system, the volume is broken up into a set of height intervals, with the collecting areas determined by the position of the active shower or sporadic source radiant. The flux per height interval is calculated and summed to obtain the total meteor flux. As the mass is also computed from the photometry, a mass flux can also be calculated. First, a weather algorithm indicates if sky conditions are clear enough to calculate fluxes, at which point a limiting magnitude algorithm is employed. The limiting magnitude algorithm performs a fit of stellar magnitudes versus camera intensities. The stellar limiting magnitude is derived from this and converted to a limiting meteor magnitude for the active shower or sporadic source. The fluxes are scaled to an average limiting magnitude throughout the night and zenithal hourly rate (ZHR's) are output daily along with flux values. In addition to this process, results will be presented as applied to the 2014 May Camelopardalid outburst, using data from several different optical systems, which looked at May Camelopardalids in different size ranges.

Blaauw, Rhiannon↗
NASA NTRS2013

Automated Meteor Fluxes with a Wide-Field Meteor Camera Network

Within NASA, the Meteoroid Environment Office (MEO) is charged to monitor the meteoroid environment in near ]earth space for the protection of satellites and spacecraft. The MEO has recently established a two ]station system to calculate automated meteor fluxes in the millimeter ]size ]range. The cameras each consist of a 17 mm focal length Schneider lens on a Watec 902H2 Ultimate CCD video camera, producing a 21.7 x 16.3 degree field of view. This configuration has a red ]sensitive limiting meteor magnitude of about +5. The stations are located in the South Eastern USA, 31.8 kilometers apart, and are aimed at a location 90 km above a point 50 km equidistant from each station, which optimizes the common volume. Both single station and double station fluxes are found, each having benefits; more meteors will be detected in a single camera than will be seen in both cameras, producing a better determined flux, but double station detections allow for non ]ambiguous shower associations and permit speed/orbit determinations. Video from the cameras are fed into Linux computers running the ASGARD (All Sky and Guided Automatic Real ]time Detection) software, created by Rob Weryk of the University of Western Ontario Meteor Physics Group. ASGARD performs the meteor detection/photometry, and invokes the MILIG and MORB codes to determine the trajectory, speed, and orbit of the meteor. A subroutine in ASGARD allows for the approximate shower identification in single station meteors. The ASGARD output is used in routines to calculate the flux in units of #/sq km/hour. The flux algorithm employed here differs from others currently in use in that it does not assume a single height for all meteors observed in the common camera volume. In the MEO system, the volume is broken up into a set of height intervals, with the collecting areas determined by the radiant of active shower or sporadic source. The flux per height interval is summed to obtain the total meteor flux. As ASGARD also computes the meteor mass from the photometry, a mass flux can be also calculated. Weather conditions in the southeastern United States are seldom ideal, which introduces the difficulty of a variable sky background. First a weather algorithm indicates if sky conditions are clear enough to calculate fluxes, at which point a limiting magnitude algorithm is employed. The limiting magnitude algorithm performs a fit of stellar magnitudes vs camera intensities. The stellar limiting magnitude is derived from this and easily converted to a limiting meteor magnitude for the active shower or sporadic source.

Blaauw, R. C.↗
NASA NTRS1984

X-ray spectra and time variability of active galactic nuclei

X ray measurements taken with the HEAO-1 and -2 satellites are examined for clues to the source of emissions from active galactic nuclei (AGN). The data covered the energy range 2-100 keV and 0.5-4.5 keV and encompassed quasars, BL Lac objects, Seyfert I galaxies and broadline radio galaxies. The broadline spectra were best fit with a power law with a slope of about 0.68. The continua displayed roughly equivalent energy at all wavelengths except for radio bands. Spectral variability was detected in the BL Lac objects, which may emit optical, UV and soft X ray radiation from optically thin synchrotron emission with a hard X ray tail from inverse Compton scattering. No strong variability was evidenced with other AGN, suggesting that the emitting regions are below the Eddington luminosity and thus exhibit stable flow characteristics.

Mushotzky, R. F.↗