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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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NASA NTRS1999

A US Coordination Facility for the Spectrum-X-Gamma Observatory

Spectrum-X Gamma (SXG) is a world-class, orbiting astronomical observatory, with capabilities for all-sky monitoring, polarimetry, and high resolution spectroscopy, and wavelength coverage extending from the ultraviolet (TAUVEX and FUVITA), through the x-ray (SODART and JET-X), to the hard x-ray (MART), and gamma-ray (SPIN) regimes. SXG is a multi-national mission developed under the sponsorship of the Russian Academy of Sciences, with participation from several European countries and the U.S. The U.S. involvement in SXG includes both instrumentation and data rights. The U.S. Spectrum X Gamma Coordination Facility (SXGCF) supports U.S. observers in proposing for SXG SODART observations, analyzing SXG data, and conducting archival research. The SXGCF also has the responsibility for organizing the U.S. archive of SXG data, which will eventually include approximately half of the data from most SXG instruments. This report summarizes the activities of the SXGCF scientific and technical staff during the period from Feb. 1 through July 31, 1999.

Forman, William R.↗
NASA NTRS1999

The U.S. Spectrum X Gamma Coordination Facility

Spectrum-X-Gamma (SXG) provides for US participation in a first-class international x-ray mission. Despite launch delays, SXG will provide unique scientific opportunities due to its capability for all-sky monitoring, polarimetry, high resolution spectroscopy, and broad wavelength range-from the ultraviolet (TAUVEX and FUVITA), through the x-ray (SODART and JET-X), to the hard x-ray (MART), and gamma-ray burst detectors. Before describing our completed work, we review the unique properties of SXG and provide some examples of the scientific importance of SXG in the Chandra, XMM, and ASTRO-E era.

Forman, William R.↗
NASA NTRS2001

The Chandra X-Ray Observatory

The Chandra X-Ray Observatory is the X-ray component of NASA's Great observatories which also includes the recently decommissioned Compton Gamma Ray Observatory, the Hubble Space Telescope, and the soon to be launched Space Infra Red Telescope Facility. Chandra is a unique X-ray astronomy facility for high-resolution imaging and for high-resolution spectroscopy. Chandra's performance advantage over other X-ray observatories is analogous to that of the Hubble Space Telescope over ground-based observatories. Chandra is a NASA facility that provides scientific data to the international astronomical community in response to proposals for its use. Data becomes public one year after the observation. The Observatory is the product of the efforts of many commercial, academic, and government organizations in the United States and Europe. NASA's Marshall Space Flight Center (MSFC) manages the Project and provides Project Science; TRW Space and Electronics Group served as prime contractor responsible for providing the spacecraft, the telescope, and assembling and testing the observatory; the Smithsonian Astrophysical Observatory (SAO) provides technical support and is responsible for ground operations.

Weisskopf, M. C.↗
NASA NTRS2002

Far Ultraviolet Astronomy

The Far Ultraviolet Spectroscopic Explorer (FUSE) is studying a wide range of astronomical problems in the 905-1187 Angstrom wavelength region through the use of high resolution spectroscopy. The FUSE bandpass forms a nearly optimal complement to the spectral coverage provided by the Hubble Space Telescope (HST), which extends down to approximately 1170 Angstroms. The photoionization threshold of atomic hydrogen (911 Angstroms) sets a natural short-wavelength limit for the FUV. FUSE was launched in June 1999 from Cape Canaveral, Florida, on a Delta II rocket into a 768 km circular orbit. Scientific observations started later that year. This spectral region is extremely rich in spectral diagnostics of astrophysical gases over a wide range of temperatures (100 K to over 10 million K). Important strong spectral lines in this wavelength range include those of neutral hydrogen, deuterium, nitrogen, oxygen, and argon (H I, D I, N I, O I, and Ar I), molecular hydrogen (H2), five-times ionized oxygen (O VI), and several ionization states of sulfur (S III - S VI). These elements are essential for understanding the origin and evolution of the chemical elements, the formation of stars and our Solar System, and the structure of galaxies, including our Milky Way. FUSE is one of NASA's Explorer missions and a cooperative project of NASA and the space agencies of Canada and France. These missions are smaller, more scientifically focused missions than the larger observatories, like Hubble and Chandra. FUSE was designed, built and operated for NASA by the Department of Physics and Astronomy at Johns Hopkins University. Hundreds of astronomers world-wide are using FUSE for a wide range of scientific research. Some of the important scientific discoveries from the first two years of the mission are described.

Sonneborn, George↗
NASA NTRS2004

Solar Flares Observed with the Ramaty High Energy Solar Spectroscopic Imager (RHESSI)

Solar flares are impressive examples of explosive energy release in unconfined, magnetized plasma. It is generally believed that the flare energy is derived from the coronal magnetic field. However, we have not been able to establish the specific energy release mechanism(s) or the relative partitioning of the released energy between heating, particle acceleration (electrons and ions), and mass motions. NASA's RHESSI Mission was designed to study the acceleration and evolution of electrons and ions in flares by observing the X-ray and gamma-ray emissions these energetic particles produce. This is accomplished through the combination of high-resolution spectroscopy and spectroscopic imaging, including the first images of flares in gamma rays. RHESSI has observed over 12,000 solar flares since its launch on February 5, 2002. I will demonstrate how we use the RHESSI spectra to deduce physical properties of accelerated electrons and hot plasma in flares. Using images to estimate volumes, w e typically find that the total energy in accelerated electrons is comparable to that in the thermal plasma. I will also present flare observations that provide strong support for the presence of magnetic reconnection in a large-scale, vertical current sheet in the solar corona. RHESSI observations such as these are allowing us to probe more deeply into the physics of solar flares.

Holman, Gordon D.↗
NASA NTRS2004

The Role of Coherent Detection

Many interesting astronomical objects, such as galaxies, molecular clouds, PDRs, star - forming regions, protostars, evolved stars, planets, and comets, have rich submillimeter spectra. In order to avoid line blending, and to be able to resolve the line shape, it is often necessary to measure these spectra at high resolution. This paper discusses the relative advantages and limitations of coherent and direct detection for high resolution spectroscopy in the submillimeter and far - infrared. In principle, direct detection has a fundamental sensitivity advantage. In practice, it is di.cult to realize this advantage given the sensitivities of existing detectors and reasonable constraints on the instrument volume. Thus, coherent detection can be expected to play an important role in submillimeter and far - infrared astrophysics well into the future.

Zmuidzinas, J.↗
NASA NTRS1998

Detection of atomic deuterium in the upper atmosphere of Mars

High-resolution spectroscopy of Mars' atmosphere with the Hubble Space Telescope revealed the deuterium Lyman alpha line at an intensity of 23 +/- 6 rayleighs. This measured intensity corresponds to HD/H2 = 1.5 +/- 0.6 x 10(-4), which is smaller by a factor of 11 than HDO/H2O. This indicates that fractionation of HD/H2 relative to that of HDO/H2O is not kinetically controlled by the rates of formation and destruction of H2 and HD but is thermodynamically controlled by the isotope exchange HD + H2O left and right arrow HDO + H2. Molecular hydrogen is strongly depleted in deuterium relative to water on Mars because of the very long lifetime of H2 (1200 years). The derived isotope fractionation corresponds to an estimate of a planetwide reservoir of water ice about 5 meters thick that is exchangeable with the atmosphere.

Flight Experiment↗
NASA NTRS2005

Lunar and Planetary Science XXXVI, Part 9

The following topics were discussed: Monitoring floods with NASA's ST6 autonomous spacecraft experiment; Dynamical cloud models constrained by high resolution spectroscopy of zodiacal light; The oxygen isotopic composition of the sun and implications for oxygen processing in molecular clouds; A nochian/hisperian hiatus and erosive reactivation of martian valley networks; Hard x-ray spectro-microscopy techniques; Thermoluminescence studies of carbonaceous chondrites, etc.

Source record↗
NASA NTRS2002

THz frequency multiplier chains base on planar Schottky diodes

The Herschel Space Observatory (HSO), an ESA cornerstone mission with NASA contribution, will enable a comprehensive study of the galactic as well as the extra galactic universe. At the heart of this exploration are ultra sensitive coherent detectors that can allow for high-resolution spectroscopy. Successful operation of these receivers is predicated on providing a sufficiently powerful local oscillator (LO) source. Historically, a versatile space qualified LO source for frequencies beyond 500 GHz has been difficult if not impossible. This paper will focus on the effort under way to develop, build, characterize and qualify a LO chain to 1200 GHz (Band 5 on HSO) that is based on planar GaAs diodes mounted in waveguide circuits. State-of-the-art performance has been obtained from a three-stage ( x2 x 2 x 3 ) multiplier chain that can provide a peak output power of 120 uW (1178 GHz) at room temperature and a peak output power of 190 uW at 1183 GHz when cooled to 113 K. Implementation of this LO source for the Heterodyne Instrument for Far Infrared (HIFI) on HSO will be discussed in detail.

oscillator spectroscopy↗
NASA NTRS2002

Terahertz technology and applications

Despite great scientific interest since at least the 1920's, the THz frequency range remains on e of the least tapped regions of the electromagnetic spectrum. Sandwiched between traditional microwave and optical technologies where there is a limited atmospheric propagation path, little commercial emphasis has been placed on THz systems. This has, perhaps fortunately, preserved some unique science and applications for tomorrow's technologies. For over 25 years the sole niche for THz technology has been in the high resolution spectroscopy and remote sensing areas where heterodyne and Fourier transform techniques have allowed astronomers, chemists, Earth, planetary and space scientists to measure, catalog and map thermal emission lines for a wide variety of lightweight molecules. As it turns out, no where else in the electromagnetic spectrum do we receive so much information about these chemical species. In fact, the universe is bathed in THz energy, most of it going unnoticed and undetected.

THz electromagnetic spectrum↗
NASA NTRS2007

Neutron Stars

Neutron stars were discovered almost 40 years ago, and yet many of their most fundamental properties remain mysteries. There have been many attempts to measure the mass and radius of a neutron star and thereby constrain the equation of state of the dense nuclear matter at their cores. These have been complicated by unknown parameters such as the source distance and burning fractions. A clean, straightforward way to access the neutron star parameters is with high-resolution spectroscopy. I will present the results of searches for gravitationally red-shifted absorption lines from the neutron star atmosphere using XMM-Newton and Chandra.

Cottam, J.↗
NASA NTRS2008

Xenia: A Probe of Cosmic Chemical Evolution

Xenia is a concept study for a medium-size astrophysical cosmology mission addressing the Cosmic Origins key objective of NASA's Science Plan. The fundamental goal of this objective is to understand the formation and evolution of structures on various scales from the early Universe to the present time (stars, galaxies and the cosmic web). Xenia will use X-and y-ray monitoring and wide field X-ray imaging and high-resolution spectroscopy to collect essential information from three major tracers of these cosmic structures: the Warm Hot Intergalactic Medium (WHIM), Galaxy Clusters and Gamma Ray Bursts (GRBs). Our goal is to trace the chemo-dynamical history of the ubiquitous warm hot diffuse baryon component in the Universe residing in cosmic filaments and clusters of galaxies up to its formation epoch (at z =0-2) and to map star formation and galaxy metal enrichment into the re-ionization era beyond z ~ 6. The concept of Xenia (Greek for "hospitality") evolved in parallel with the Explorer of Diffuse Emission and GRB Explosions (EDGE), a mission proposed by a multinational collaboration to the ESA Cosmic Vision 2015. Xenia incorporates the European and Japanese collaborators into a U.S. led mission that builds on the scientific objectives and technological readiness of EDGE.

Kouveliotou, Chryssa↗
NASA NTRS2008

Joint XMM-Newton, Chandra, and RXTE Observations of Cyg X-1 at Phase Zero

We present first results of simultaneous observations of the high mass X-ray binary Cyg X-1 for 50 ks with XMM-Newton, Chandra-HETGS and RXTE in 2008 April. The observations are centered on phase 0 of the 5.6 d orbit when pronounced dips in the X-ray emission from the black hole are known to occur. The dips are due to highly variable absorption in the accretion stream from the O-star companion to the black hole. Compared to previous high resolution spectroscopy studies of the dip and non-dip emission with Chandra, the addition of XMM-Newton data allows for a better determination of the continuum, especially through the broad iron line region (with RXTE constraining the greater than 10 keV continuum).

Pottschmidt, Katja↗
NASA NTRS2008

X-ray Timing Measurements

We present new, extended X-ray timing measurements of the ultra-compact binary candidates V407 Vul and RX J0806.3+1527 (J0806), as well as a summary of the first high resolution X-ray spectra of 50806 obtained with the Chandra/LETG. The temporal baseline for both objects is approximately 12 years, and our measurements confirm the secular spin-up in their X-ray periods. The spin-up rate in 50806 is remarkably uniform at 3.55x10(exp -16)Hz/s, with a measurement precision of 0.2%. We place a limit (90% confidence) on 1 d dot nu < 4x10(exp -26)Hz/sq s. Interestingly, for V407 Vul we find the first evidence that the spin-up rate is slowing, with d dot\nu = -2.8 pm 1x10(exp -26)Hz/sq s. This provides the first indication that torques in addition to gravitational radiation are present in V407 Vul. Further monitoring could constrain the nature of the torque, as either accretion induced or due to unipolar induction. We also obtained the first high resolution X-ray spectrum of J0806 with an 80 ksec Chandra/LETG observation. We find evidence for emission features in the 25-50 AA range, with the strongest feature centered at 27 AA. The spectrum appears largely devoid of common lines of oxygen, nitrogen and neon, and we suggest the 27 AA feature may be associated with heavier species, such as magnesium, silicon or sulphur. Deeper observations will be needed to fully exploit the strong diagnostic potential of high resolution spectroscopy for these objects.

Strohmayer, T.↗
NASA NTRS2010

The EXIST Infra-Red Telescope System: Design and Performance

The Infra-Red Telescope is a critical element of the EXIST (Energetic X-Ray Imaging Survey Telescope) observatory. It is a passively cooled 1.lm visible/infrared telescope. The primary goal of the IRT is to obtain photometric and spectroscopic measurements of high redshift (>6) gamma ray burst afterglows to study the nature of these enigmatic events and their environments, and to use them as probes of the composition and ionization state of the intergalactic medium of the young universe. The IRT will provide a prompt follow up (within three minutes) of the transient discovered by the EXIST with exceptional NIR sensitivity (AB=24 in 100s) surpassing HST in the infrared due to its passively cooled (- 30 C) mirror. Its optical design and spectral coverage is tailored to the high redshift transient events that require prompt pointing, identification, accurate photometry and both low and high resolution spectroscopy. Here we describe the telescope, its instrument complement, and the cooling systems which provide its remarkable sensitivity

Moseley, Samuel H.↗
NASA NTRS2010

Mode Tracker for Mode-Hop-Free Operation of a Laser

A mode-tracking system that includes a mode-controlling subsystem has been incorporated into an external-cavity (EC) quantum cascade laser that operates in a mid-infrared wavelength range. The mode-tracking system makes it possible to perform mode-hop-free wavelength scans, as needed for high-resolution spectroscopy and detection of trace gases. The laser includes a gain chip, a beam-collimating lens, and a diffraction grating. The grating is mounted on a platform, the position of which can be varied to effect independent control of the EC length and the grating angle. The position actuators include a piezoelectric stage for translation control and a motorized stage for coarse rotation control equipped with a piezoelectric actuator for fine rotation control. Together, these actuators enable control of the EC length over a range of about 90 m with a resolution of 0.9 nm, and control of the grating angle over a coarse-tuning range of +/-6.3deg and a fine-tuning range of +/-520 microrad with a resolution of 10 nrad. A mirror mounted on the platform with the grating assures always the same direction of the output laser beam.

Wysocki, Gerard↗
NASA NTRS2010

Role of the Chandra X-Ray Observatory Observations for the Study of Ionized Plasmas

The Chandra X-Ray Observatory, launched in 1999, is now beginning its 12-th year of operation. Chandra, the X-ray component of NASA s Great Observatory program, continues to operate efficiently, somewhat remarkable considering that the Observatory was designed for three years of operation with a goal of five. The Observatory features X-ray optics with sub-arcsecond angular resolution and a small suite of instruments, including transmission gratings, which allow for high-resolution spectroscopy of point sources. We will detail the capabilities of the Observatory for making such spectroscopic measurements and discuss a number of examples of what has been learned about the astrophysical plasmas capable of producing bright X-ray emission.

Weisskopf, Martin C.↗