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NASA NTRS1998

Spatially Resolved Spectra of 3C Galaxy Nuclei

We present and discuss visible-wavelength long-slit spectra of four low-redshift 3C galaxies obtained with the Space Telescope Imaging Spectrograph on the Hubble Space Telescope (HST). The slit was aligned with near-nuclear jet-like structure seen in HST images of the galaxies, to give unprecedented spatial resolution of their inner regions. In 3C 135 and 3C 171, the spectra reveal clumpy emission-line structures that indicate outward motions of a few hundred kilometers per second within a centrally illuminated and ionized biconical region. There may also be some low-ionization, high-velocity material associated with 3C 135. In 3C 264 and 3C 78, the jets have blue featureless spectra consistent with their proposed synchrotron origin. There is weak associated line emission in the innermost part of the jets with mild outflow velocity. These jets are bright and highly collimated only within a circumnuclear region of lower galaxy luminosity, which is not dusty. We discuss the origins of these central regions and their connection with relativistic jets.

Hutchings, J. B.↗

NASA NTRS1992

Description of a prototype emission-transmission computed tomography imaging system

We have developed a prototype imaging system that can perform simultaneous x-ray transmission CT and SPECT phantom studies. This system employs a 23-element high-purity-germanium detector array. The detector array is coupled to a collimator with septa angled toward the focal spot of an x-ray tube. During image acquisition, the x-ray fan beam and the detector array move synchronously along an arc pivoted at the x-ray source. Multiple projections are obtained by rotating the object, which is mounted at the center of rotation of the system. The detector array and electronics can count up to 10(6) cps/element with sufficient energy-resolution to discriminate between x-rays at 100-120 kVp and gamma rays from 99mTc. We have used this device to acquire x-ray CT and SPECT images of a three-dimensional Hoffman brain phantom. The emission and transmission images may be superimposed in order to localize the emission image on the transmission map.

NASA Discipline Musculoskeletal↗

NASA NTRS1989

Space vehicle approach velocity judgments under simulated visual space conditions

There were 35 volunteers who responded when they first perceived an increase in apparent size of a collimated, two-dimensional perspective image of an Orbiter vehicle. The variables of interest included the presence (or absence) of a fixed reticle within the field of view (FOV), background starfield velocity, initial range to the vehicle and vehicle closure velocity. It was found that: 1) increasing vehicle approach velocity yielded a very small (but significant) effect of faster detection of vehicle movement, nevertheless, response variability was relatively large; 2) including the fixed reticle in the FOV produced significantly slower detection of vehicle radial movement, however this occurred only at the largest range and the magnitude of the effect was only about 15% of the one sigma value; and 3) increasing background star velocity during this judgment led to slower detection of vehicle movement. While statistically significant, this effect was small and occurred primarily at the largest range. A possible explanation for the last two findings is that other static and dynamic objects within the visual field may compete for available attention which otherwise would be available for judging image expansion; thus, the target's retinal image has to expand more than otherwise for its movement to be detected. This study also showed that the Proximity Operations Research Mockup at NASA/Ames can be used effectively to investigate a variety of visual judgment questions related to future space operations. These findings are discussed in relation to previous research and possible underlying mechanisms.

Space Flight↗

NASA NTRS2004

Laboratory Measurement of Bidirectional Reflectance of Radiometric Tarps

This experiment measured the reflectance of tarps with ground instruments in order to check radiometric calibration, validate atmospheric correction, and predict at-sensor radiance for satellite instruments. The procedure of this experiment is as follows: 1) Assemble laboratory apparatus to duplicate ground reference measurement geometry and satellite measurement geometry; 2) Measure spectral radiance with Optronics OL 750 double monochromator/spectroradiometer; 3) Measure radiance of NIST-calibrated Spectralon panel irradiated by collimated light at incidence angle of calibrated reflectance (20 deg, 30 deg, 40 deg, or 50 deg), viewing normal to panel surface; 4) Measure radiance of Spectralon panel irradiated at incidence angle equal to solar zenith angle at time of overpass; 5) Calculate reflectance of Spectralon panel irradiated at solar zenith angle, viewing normal to panel surface (ground geometry).

Knowlton, Kelly↗

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 NTRS2004

Calibration of the Rossi X-ray Timing Explorer Proportional Counter Array

We present the calibration and background model for the Proportional Counter Array (PCA) aboard the Rossi X-ray Timing Explorer (RXTE). The energy calibration is systematics limited below 10 keV with deviations from a power law fit to the Crab nebula plus pulsar loss than 1%. Unmodelled variations in the instrument background amount to less than 2% of the observed background below 10 keV and less than 1% between 10 and 20 keV. Individual photon arrival times are accurate to 4.4 microseconds at all times during the mission and to 2.5 microseconds after 29 April 1997. The peak pointing direction of the five collimators is known at few arcsecond precision.

Jahoda, Keith↗

NASA NTRS2005

Holographic Optical Elements as Scanning Lidar Telescopes

We have developed and investigated the use of holographic optical elements (HOEs) and holographic transmission gratings for scanning lidar telescopes. For example, rotating a flat HOE in its own plane with the focal spot on the rotation axis makes a very simple and compact conical scanning telescope. We developed and tested transmission and reflection HOEs for use at the first three harmonic wavelengths of Nd:YAG lasers. The diffraction efficiency, diffraction angle, focal length, focal spot size and optical losses were measured for several HOEs and holographic gratings, and found to be suitable for use as lidar receiver telescopes, and in many cases could also serve as the final collimating and beam steering optic for the laser transmitter. Two lidar systems based on this technology have been designed, built, and successfully tested in atmospheric science applications. This technology will enable future spaceborne lidar missions by significantly lowering the size, weight, power requirement and cost of a large aperture, narrow field of view scanning telescope.

Schwemmer, Geary K.↗

NASA NTRS2005

[School-Based UV-B Monitoring Project in Support of EOS-CHEM]

This grant is an extension of Grant NAG5-8929 (Drexel Project Number 230026), resulting from extensions necessary to meet changing science objectives as described in the final report for NAG5-8929, a copy of which is attached. The instrument configuration resulting from NAG54929 has remained basically intact. Cosine response measurements conducted by James Slusser s group at Fort Collins, Colorado, in support of the proposal for Aura ground validation mentioned in the final report for NAG5-8929, indicated that there was significant light leakage to the detector through the sides of the nylon housing. This was easily remedied by machining a removable opaque collar (made from the dark same grey rigid plastic plumbing tubing as the collimating tube) that fits around the detector collar. Also during this grant period, data logging procedures were established for the UV-A instrument, to record irradiance before, during, and after an Aura overflight. This is required in order to compare spatial and temporal variability as required for ground validation of data products derived from the Ozone Monitoring Instrument (OMI). Standalone 12-bit loggers from Onset Computer Corporation (the U12 series), which were not available at the start of these projects, makes possible relatively inexpensive logging for these instruments at a usable resolution. configuration and disposition of these instruments, including the final version of a GLOBE protocol for using the instruments, currently depend on action taken on the Aura ground validation proposal submitted in 2004. A copy of that proposal is attached.

Brooks, David R.↗

NASA NTRS2005

Outbursts in Symbiotic Binaries

A major question for symbiotic stars concerns the nature and cause of their outbursts. A small subset of symbiotics, the slow novae are fairly well established as thermonuclear events that last on the order of decades. The several symbiotic recurrent novae, which are much shorter and last on the order of months, are also thought to be thermonuclear runaways. Yet the majority of symbiotics are neither slow novae nor recurrent novae. These are the so-called classical symbiotics, many of which show outbursts whose cause is not well understood. In some cases, jets are produced in association with an outburst, therefore an investigation into the causes of outbursts will yield important insights into the production of collimated outflows. To investigate the cause and nature of classical symbiotic outbursts, we initiated a program of multiwavelength observations of these events. In FUSE Cycle 2, we obtained six observational epochs of the 2000-2002 classic symbiotic outburst in the first target of our campaign - class prototype, Z Andromedae. That program was part of a coordinated multi-wavelength Target-of-Opportunity (TOO) campaign with FUSE, XMM, Chandra, MERLIN, the VLA, and ground-based spectroscopic and high time-resolution photometric observations. Our campaign proved the concept, utility, and need for coordinated multi-wavelength observations in order to make progress in understanding the nature of the outburst mechanisms in symbiotic stars. Indeed, the FUSE data were the cornerstone of this project

Sonneborn, George↗

NASA NTRS2005

Outbursts in Symbiotic Binaries: Z and Continued Observation

A major question for symbiotic stars concerns the nature and cause of their outbursts. A small subset of symbiotics, the "slow novae" are fairly well established as thermonuclear events that last on the order of decades. The several symbiotic "recurrent novae", which are much shorter and last on the order of months, are also thought to be thermonuclear runaways. Yet the majority of symbiotics are neither slow novae nor recurrent novae. These are the so-called "classical symbiotics," many of which show outbursts whose cause is not well understood. In some cases, jets are produced in association with an outburst, therefore an investigation into the causes of outbursts will yield important insights into the production of collimated outflows. To investigate the cause and nature of classical symbiotic outbursts, we initiated a program of multi- wavelength observations of these events. First of all in FUSE Cycle 2, we obtained six observational epochs of the 2000-2002 classic symbiotic outburst in the first target of our campaign - class prototype, Z Andromedae. That program was part of a coordinated multi-wavelength Target-of-Opportunity (TOO) campaign with FUSE, XMM, Chandra, MERLIN, the VLA, and ground-based spectroscopic and high time-resolution photometric observations. Our campaign proved the concept, utility, and need for coordinated multi-wavelength observations in order to make progress in understanding the nature of the outburst mechanisms in symbiotic stars. Indeed, the FUSE data were the cornerstone of this project. The present program is a continuation of that cycle 2 effort. Indeed, the observations acquired in this program are vital to the proper interpretation of the material acquired in cycle 2 as the new data cover the critical time period when the star continues to decline from outburst and actually returns to quiescence. The utilization of these data have allowed us to refine and complete description of our new model for classical symbiotic system outbursts.

Sonneborn, George↗

NASA NTRS2005

Design and Performance of a Triple Source Air Mass Zero Solar Simulator

Simulating the sun in a laboratory for the purpose of measuring solar cells has long been a challenge for engineers and scientists. Multi-junction cells demand higher fidelity of a solar simulator than do single junction cells, due to a need for close spectral matching as well as AM0 intensity. A GaInP/GaAs/Ge solar cell for example, requires spectral matching in three distinct spectral bands (figure 1). A commercial single source high-pressure xenon arc solar simulator such as the Spectrolab X-25 at NASA Glenn Research Center, can match the top two junctions of a GaInP/GaAs/Ge cell to within 1.3% mismatch, with the GaAs cell receiving slightly more current than required. The Ge bottom cell however, is mismatched +8.8%. Multi source simulators are designed to match the current for all junctions but typically have small illuminated areas, less uniformity and less beam collimation compared to an X-25 simulator. It was our intent when designing a multi source simulator to preserve as many aspects of the X-25 while adding multi-source capability.

Jenkins, Phillip↗

NASA NTRS2005

Large Field-of-View KD*P Modulator for Solar Polarization Measurements

This paper will describe the evolution of the Marshall Space Flight Center electro-optical polarimeter with emphasis on the field of view characteristics of the its KD*P modulator. Understanding the field of view characteristics was essential to the success of the MSFC vector magnetograph. The paper will show how the field of view errors of KD*P look similar to the polarization patterns seen in simple sunspots and why the placement of the KD*P in a collimated beam was essential in separating the instrumental polarization from the solar signal. Finally, this paper will describe a modulator design which minimizes those field-of-view errors.

West, E. A.↗

NASA NTRS1991

Solar-A Prelaunch Mission Operation Report (MOR)

The Solar-A mission is a Japanese-led program with the participation of the United States and the United Kingdom. The Japanese Institute of Space and Astronautical Science (ISAS) is providing the Solar-A spacecraft, two of the four science instruments, the launch vehicle and launch support, and the principal ground station with Operational Control Center. NASA is providing a science instrument, the Soft X-ray Telescope (SXT)and tracking support using the Deep Space Network (DSN) ground stations. The United Kingdom s Science and Engineering Research Council (SERC) provides the Bragg Crystal Spectrometer. The Solar-A mission will study solar flares using a cluster of instruments on a satellite in a 600 km altitude, 31 degree inclination circular orbit. The emphasis of the mission is on imaging and spectroscopy of hard and soft X-rays. The principal instruments are a pair of X-ray imaging instruments, one for the hard X-ray range and one for the soft X-ray range. The Hard X-Ray Telescope (HXT), provided by ISAS, operates in the energy range of 10-100 keV and uses an array of modulation collimators to record Fourier transform images of the non-thermal and hot plasmas that are formed during the early phases of a flare. These images are thought to be intimately associated with the sites of primary energy release. The Soft X-Ray Telescope (SXT), jointly provided by NASA and ISAS, operates in the wavelength range of 3-50 Angstroms and uses a grazing incidence mirror to form direct images of the lower temperature (but still very hot) plasmas that form as the solar atmosphere responds to the injection of energy. The SXT instrument is a joint development effort between the Lockheed Palo Alto Research Laboratory and the National Astronomical Observatory of Japan. The U.S. effort also involves Stanford University, the University of California at Berkeley and the University of Hawaii, who provide support in the areas of theory, data analysis and interpretation, and ground-based observations. The hard and soft X-ray telescopes both have an alignment sensor, operating in the visual region of the spectrum, to provide co-alignment information.

Source record↗

NASA NTRS2005

Large Field-of-view KD*P Modulator for Solar Polarization Measurements

West, Edward A.↗

NASA NTRS2006

Single-Pulse Multi-Point Multi-Component Interferometric Rayleigh Scattering Velocimeter

A simultaneous multi-point, multi-component velocimeter using interferometric detection of the Doppler shift of Rayleigh, Mie, and Rayleigh-Brillouin scattered light in supersonic flow is described. The system uses up to three sets of collection optics and one beam combiner for the reference laser light to form a single collimated beam. The planar Fabry-Perot interferometer used in the imaging mode for frequency detection preserves the spatial distribution of the signal reasonably well. Single-pulse multi-points measurements of up to two orthogonal and one non-orthogonal components of velocity in a Mach 2 free jet were performed to demonstrate the technique. The average velocity measurements show a close agreement with the CFD calculations using the VULCAN code.

Bivolaru, Daniel↗

NASA NTRS2006

Discharge Chamber Plasma Structure of a 30-cm NSTAR-Type Ion Engine

Single Langmuir probe measurements are presented over a two-dimensional array of locations in the near Discharge Cathode Assembly (DCA) region of a 30-cm diameter ring cusp ion thruster over a range of thruster operating conditions encompassing the high-power half of the NASA throttling table. The Langmuir probe data were analyzed with two separate methods. All data were analyzed initially assuming an electron population consisting of Maxwellian electrons only. The on-axis data were then analyzed assuming both Maxwellian and primary electrons. Discharge plasma data taken with beam extraction exhibit a broadening of the higher electron temperature plume boundary compared to similar discharge conditions without beam extraction. The opposite effect is evident with the electron/ion number density as the data without began, extraction appears to be more collimated than the corresponding data with beam extraction. Primary electron energy and number densities are presented for one operating condition giving an order of magnitude of their value and the error associated with this calculation.

Herman, Daniel A.↗

NASA NTRS2006

Short Haul Civil Tiltrotor Contingency Power System Preliminary Design

Eames, David J. H.↗

NASA NTRS2006

Confirmation of the E(sup src)(sub Peak)-E(sub iso) (Amati) relation from the x-ray flash XRF 050416A observed by the Swift burst alert telescope

We report Swift Burst Alert Telescope (BAT) observations of the X-ray flash (XRF) XRF 050416A. The fluence ratio between the 15-25 and 25-50 keV energy bands of this event is 1.5, thus making it the softest gamma-ray burst (GRB) observed by BAT so far. The spectrum is well fitted by a Band function with E(sup obs)(sub peak) of 15.0(sup +2.3)(sub -2.7) keV. Assuming the redshift of the host galaxy (z = 0.6535), the isotropic equivalent radiated energy E(sub iso) and the peak energy at the GRB rest frame (E(sup src)(sub peak)) of XRF 050416A are not only consistent with the correlation found by Amati et al. and extended to XRFs by Sakamoto et al. but also fill in the gap of this relation around the 30-80 keV range of E(sup src)(sub peak). This result tightens the validity of the E(sup src)(sub Peak)-E(sup src)(sub peak) relation from XRFs to GRBs. We also find that the jet break time estimated using the empirical relation between E(sup src)(sub peak) and the collimation corrected energy E(sub gamma), is inconsistent with the afterglow observation by the Swift X-Ray Telescope. This could be due to the extra external shock emission overlaid around the jet break time or to the nonexistence of a jet break feature for XRFs, which might be a further challenge for GRB jet emission models and XRF/GRB unification scenarios.

Sakamoti, T.↗