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At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Remote sensing of mesospheric winds with the High-Resolution Doppler Imager

Observations of the winds in the upper atmosphere obtained with the High-Resolution Doppler Imager (HRDI) on the Upper Atmosphere Research Satellite (UARS) are discussed. This instrument is a very stable high-resolution triple-etalon Fabry-Perot interferometer, which is used to observe the slight Doppler shifts of absorption and emission lines in the O2 Atmospheric bands induced by atmospheric motions. Preliminary observations indicate that the winds in the mesosphere and lower thermosphere are a mixture of migrating and non-migrating tides, and planetary-scale waves. The mean meridional winds are dominated by the 1,1 diurnal tide which is easily extracted from the daily zonal means of the satellite observations. The daily mean zonal winds are a mixture of the diurnal tide and a zonal flow which is consistent with theoretical expectations.

Hays, Paul B.↗
NASA NTRS1982

Ultra high resolution molecular beam cars spectroscopy with application to planetary atmospheric molecules

The measurement of high resolution pulsed and continuous wave (CW) coherent anti-Stokes Raman spectroscopy (CARS) measurements in pulsed and steady state supersonic expansions were demonstrated. Pulsed molecular beam sources were characterized, and saturation of a Raman transition and, for the first time, the Raman spectrum of a complex molecular cluster were observed. The observation of CW CARS spectra in a molecular expansion and the effects of transit time broadening is described. Supersonic expansion is established as a viable technique for high resolution Raman spectroscopy of cold molecules with resolutions of 100 MH2.

Byer, R. L.↗
NASA NTRS1995

Hardness Assurance and Testing Techniques for High Resolution (12- to 16-bit) Analog-to-Digital Converters

Discussed are hardness assurance and testing techniques to test and evaluate total dose radiation degradation of high resolution A/D converters. Because high-speed, high-resolution converters are critical parts in a digital signal processing or data acquisition system, the evaluation of performance in the early design phase is very important. Converters from three manufacturers are evaluated.

Analog-to-Digital↗
NASA NTRS1973

High resolution studies of the solar X-ray corona from Aerobee rockets

The research in high resolution solar X-ray astronomy is reported. The payload for the Aerobee 150 launch vehicle, which included a 23 cm diameter mirror whose polished surface was a nickel-phosphorus alloy is discussed along with the high resolution measurements, by Flight 13.028 CS, of the temperature and density structure of the lower corona. Flight 13.029 CS is also discussed.

Davis, J. M.↗
NASA NTRS2008

"Long-term Timing and High Resolution Spectroscopy of Ultracompact Candidates V407 Vul and RX J0806.3+1527"

We present new, extended X-ray timing measurements of the ultracompact binary candidates V407 Vul and RX J0806.3+1527 (J0806), as well as a summary of the first high resolution X-ray spectrum of 50806 obtained with the Chandra/LETG. The temporal baseline for both objects is about 12 years, and our measurements confirm the secular spin-up of their X-ray periods. The spin-up rate in J0806 is remarkably uniform at 3.55x10(exp -16) Hz/s, with a measurement precision of 0.2%, and we place a limit (90% confidence) on [dn/dt] < 4x10(exp -26) Hz/sq s. Interestingly, for V407 Vul we find the first evidence that the spin-up rate is slowing, with d(sup 2)n/dt(sup 2) = -2.8+/- 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 Angstrom range, with the strongest feature centered at 27 Angstrom. The spectrum appears largely devoid of common lines of oxygen, nitrogen and neon, and we suggest the 27 Angstrom feature may be associated with heavier species, such as magnesium, silicon or sulphur. Deeper observations will be needed to fully exploit the apparently strong diagnostic potential of high resolution spectroscopy for these objects.

Strohmayer, Tod↗
NASA NTRS1987

HIRIS (High-Resolution Imaging Spectrometer: Science opportunities for the 1990s. Earth observing system. Volume 2C: Instrument panel report

The high-resolution imaging spectrometer (HIRIS) is an Earth Observing System (EOS) sensor developed for high spatial and spectral resolution. It can acquire more information in the 0.4 to 2.5 micrometer spectral region than any other sensor yet envisioned. Its capability for critical sampling at high spatial resolution makes it an ideal complement to the MODIS (moderate-resolution imaging spectrometer) and HMMR (high-resolution multifrequency microwave radiometer), lower resolution sensors designed for repetitive coverage. With HIRIS it is possible to observe transient processes in a multistage remote sensing strategy for Earth observations on a global scale. The objectives, science requirements, and current sensor design of the HIRIS are discussed along with the synergism of the sensor with other EOS instruments and data handling and processing requirements.

Source record↗
NASA NTRS2008

Fabricating High-Resolution X-Ray Collimators

A process and method for fabricating multi-grid, high-resolution rotating modulation collimators for arcsecond and sub-arcsecond x-ray and gamma-ray imaging involves photochemical machining and precision stack lamination. The special fixturing and etching techniques that have been developed are used for the fabrication of multiple high-resolution grids on a single array substrate. This technology has application in solar and astrophysics and in a number of medical imaging applications including mammography, computed tomography (CT), single photon emission computed tomography (SPECT), and gamma cameras used in nuclear medicine. This collimator improvement can also be used in non-destructive testing, hydrodynamic weapons testing, and microbeam radiation therapy.

Appleby, Michael↗
NASA NTRS2018

The Volatile Composition of Comet C/2017 E4 (Lovejoy) before its Disruption, as Revealed by High-Resolution Infrared Spectroscopy with iSHELL at the NASA/IRTF

In 2017 April, we acquired comprehensive high-resolution spectra of newly discovered comet C/2017 E4 (Lovejoy) as it approached perihelion, and before its disintegration. We detected many cometary emission lines in the range (2.8-5.3) μm, in four customized instrument settings (L1-c, L3, Lp1-c, and M1) of iSHELL-the new near-IR high-resolution immersion echelle spectrograph at NASA/IRTF (Maunakea, Hawaii). We identified 12 molecular species: nine primary volatiles (H2O, HCN, NH3, CO, C2H2, C2H6, CH4, CH3OH, H2CO) and three product species (CN, NH2, OH). We detected 85 H2O emission lines from 12 water vibrational bands across L1-c and M1 settings. The many detected water emission lines enabled retrieval of accurate measures for ortho- and para-H2O independently, thereby reducing systematic uncertainty in the derived ortho-para ratio and nuclear spin temperature. Excitation analyses and emission profile analyses were performed for all species, and molecular abundance ratios relative to water are compared with values found for other Oort Cloud comets in our infrared database. Abundance ratios are consistent for most species, with the exception of underabundant methanol and overabundant ammonia in E4.

Faggi, S.↗
NASA NTRS1986

Flare stars and solar bursts - High resolution in time and frequency

Coronal loops on the sun and nearby stars are studied using observations at 20-cm wavelength with high resolution in time and frequency. Observations of the dwarf M star AD Leonis with high time resolution led to the discovery of a quasi-periodic train of circularly polarized spikes with a mean periodicity of 32 + or - 5 ms and a total duration of 150 ms. Observations at closely spaced wavelengths using the VLA revealed a narrow-band structure in solar bursts and in the slowly varying radiation of the dwarf M star YZ Canis Minoris. This narrow-band emission may be attributed to electron-cyclotron maser radiation. Maser action at the second or first harmonic of the gyrofrequency implies magnetic field strengths of 250 and 500 G, respectively. Hence, observations with high resolution in time and frequency suggest coherent processs in the coronas of the sun and dwarf M stars. It is noted that the scientific potential suggested by the present data can be realized by the development of a solar-stellar synthesis radiotelescope. This instrument would be dedicated to solar and stellar observations with high angular, temporal, and frequency resolution.

Lang, K. R.↗
NASA NTRS1996

Parallelization and Algorithmic Enhancements of High Resolution IRAS Image Construction

The Infrared Astronomical Satellite caried out a nearly complete survey of the infrared sky, and the survey data are important for the study of many astrophysical phenomena. However, many data sets at other wavelengths have higher resolutions than that of the co-added IRAS maps, and high resolution IRAS images are strongly desired both for their own information content and their usefulness in correlation. The HIRES program was developed by the Infrared Processing and Analysis Center (IPAC) to produce high resolution (approx. 1') images from IRAS data using the Maximum Correlation Method (MCM). We describe the port of HIRES to the Intel Paragon, a massively parallel supercomputer, other software developments for mass production of HIRES images, and the IRAS Galaxy Atlas, a project to map the Galactic plane at 60 and 100(micro)m.

Satellite infrared IRAS IRAS maps IRAS images↗
NASA NTRS1983

A comparison of high resolution optical and radio observations of W3

High resolution maps of the W3 complex for radio continuum and selected optical emission lines are used to derive the visual extinction A(V), the excitation, and the evolutionary state of the component H II regions. A large diffuse H II region in the east, which is the most highly evolved of this type, is found, together with a southern complex of H II regions and a northern complex of young and compact H II regions still embedded in the W3 molecular core. A comparison of the observed dust distribution with ionized and atomic hydrogen and several other molecules in W3 shows the functional relationship between the C-130 column density and A(V) to be in accord with Strohacker's (1978) result for dark clouds.

Dickel, H. R.↗
NASA NTRS1982

High-resolution continuous-wave coherent anti-Stokes Raman spectroscopy in a supersonic jet

High-resolution CW coherent anti-Stokes Raman spectra of the nu1 Q branch of methane in an underexpanded supersonic jet were obtained at temperatures as low as 31.5 K and pressures as low as 2 torr. The experimental spectra were well fitted by the calculated theoretical spectra, including transit-time broadening. A temperature of 31.5 K produced the best fit to the data, and the transit-time broadening was comparable to the residual Doppler broadening of about 100 MHz. The supersonic jet provides a convenient method of obtaining molecular cooling at relatively high density, and the ease of construction and the wide range of temperatures and densities available make it a useful tool for high resolution molecular spectroscopy.

Gustafson, E. K.↗
NASA NTRS2018

Alignment and Bonding of Silicon Mirrors for High-Resolution Astronomical X-Ray Optics [10699-141]

Future large x-ray astronomy missions require large area and high resolution. The present consensus is to integrate thin, lightweight, segmented mirrors to form a compact but large telescope with high resolution (better than 1 sec). Key technologies: 1) Accurate mirror substrates: polishing high quality mono-crystalline silicon. 2) Stress-free reflective coating: stress-based distortion cancellation. 3) Precise alignment and integration: kinematic mounting and distortion-free bonding. Four-point alignment for quasi-cylindrically symmetric mirrors (segments) - 4-Point alignment: Pitch and yaw angles, image center (X, Y) are controlled by heights of the 4 mount points; Alignment Precision: better than 1 sec; Bonding error: approx. 0.1 micrometers (approx. 1 sec); Current single mirror pair x-ray tested: 3 sec (Half-Power Diameter). Integration into (meta) shell: Shell structure has rotationally defined axis; Interlocking mirrors means lightweight, mechanically strong telescope.

Chan, Kai-Wing↗
NASA NTRS1983

Spontaneous Raman scattering as a high resolution XUV radiation source

A type of high resolution XUV radiation source is described which is based upon spontaneous anti-Stokes scattering of tunable incident laser radiation from atoms excited to metastable levels. The theory of the source is summarized and two sets of experiments using He (1s2s)(1)S atoms, produced in a cw hollow cathode and in a pulsed high power microwave discharge, are discussed. The radiation source is used to examine transitions originating from the 3p(6) shell of potassium. The observed features include four previously unreported absorption lines and several sharp interferences of closely spaced autoionizing lines. A source linewidth of about 1.9 cm(-1) at 185,000 cm(-1) is demonstrated.

Rothenberg, J. E.↗
NASA NTRS1983

Spontaneous Raman scattering as a high-resolution XUV radiation source

A type of high resolution XUV radiation source is described which is based upon spontaneous anti-Stokes scattering of tunable incident laser radiation from atoms excited to metastable levels. The theory of the source is summarized and two sets of experiments using He (1s2s)(1)S atoms, produced in a CW hollow cathode and in a pulsed high power microwave discharge, are discussed. The radiation source is used to examine transitions originating from the 3p(6) shell of potassium. The observed features include four previously unreported absorption lines and several sharp interferences of closely spaced autoionizing lines. A source linewidth of about 1.9 cm(-1) at 185,000 cm(-1) is demonstrated. Previously announced in STAR as N83-18422

Rothenberg, J. E.↗
NASA NTRS1998

A Very High Resolution Mid Infrared Spectrograph for SOFIA

The purpose of this project was to study the design of a high resolution mid-infrared spectrograph for the SOFIA airborne observatory. The primary motivation for the construction and use of such an instrument is the study of vibrational transitions of molecules in molecular clouds, circumstellar inflows and outflows, and planetary atmospheres, which are blocked from ground-based observations by absorption by the Earth's atmosphere. The instrument design studied is a cross-dispersed grating spectrograph with several modes of operation giving spectral resolving powers of approximately 4000, 20,000, and 100,000. In the two lower resolution modes a single grating is used in a long-slit spectrograph. At high resolution that grating serves as the cross-disperser for a 1-m long echelon, a very coarsely and steeply ruled grating, diamond-machined in aluminum. Several design study tasks were carried out: 1. An optical and mechanical design was developed. It differed from the preliminary design by using a reflecting focal reducer in the fore-optics and by rearranging the echelon and cross-dispersing chambers to improve the efficiency of the long-slit modes. 2. A finite-element analysis of the dewar and echelon support structures was done. It led us to change the echelon support to improve its rigidity. 3. Further information was obtained which convinced us that Hyperfine Inc. was capable of diamond-machining the echelon. 4. Several possible vendors of readout electronics and software were identified. It was decided that it is more cost-effective to purchase these items rather than developing them ourselves. 5. Observing and calibration procedures were studied. we did not identify significant changes needed from procedures used previously. 6. Possible expansions of instrument capabilities, including wavelength coverage, were studied. It appears unlikely that the echelon will perform well at wavelengths shortward of 5 microns, but the spectral coverage could be extended longward of 28 microns with the use of an Si:Sb detector. No patentable inventions were made during this study. Based on this design study, a proposal was submitted to construct the instrument. It was chosen as one of the first-light instruments for SOFIA.

Lacy, John H.↗
NASA NTRS1977

Measurement of magnetic field aligned potential differences using high resolution conjugate photoelectron energy spectra

Simultaneous high-resolution observations of a distinctive feature in the energy spectrum of conjugate photoelectrons and spacecraft potential relative to the local ionosphere have allowed the net potential difference between magnetic conjugate points at latitudes below the region of low-energy (i.e., lower than 100 eV) auroral electron precipitation to be determined. Measurements made at 300 km from Atmosphere Explorer C show that there is normally no net potential difference between hemispheres in this region, which extended up to invariant latitudes as high as 74 deg. Two types of apparently related anomalous behavior were infrequently observed at high latitudes. During these periods the incident flux of conjugate photoelectrons was either decelerated by about 3 eV or was not detected.

Peterson, W. K.↗
NASA NTRS1990

A high resolution echelle spectrometer for soft X-ray and EUV astronomy

A new design is presented for high resolution spectroscopy from 80 to 400 A. This design employs grazing incidence optics and variable line-spaced gratings to achieve high resolution. Unlike some previously proposed EUV echelles, this design employs straight groove planar gratings, which are a well-proven, easily manufactured design. The instrument delivers a peak resolution of 7500 and a peak effective area of 3 sq cm.

Green, James↗