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  • ASTRONOMY  (3)
  • INSTRUMENTATION AND PHOTOGRAPHY  (2)
  • OCEANOGRAPHY  (2)
  • Astrophysics; Astronomy  (1)
  • 1
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    Medusa spectroscopy of A400, A576, A1767, and A2124 (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Galaxy velocity data taken with the Steward Observatory multiple aperture fiber optic spectrograph are presented for four Abell clusters. The root-mean-square external errors in these velocities are about 100 km/s; accuracy which compares favorably with that obtained from single-object observations. It is expected that the recent adoption of a CCD detector should decrease external errors to about 50 km/s. All four of the clusters observed are known X-ray sources and the present data agree well with empirically derived velocity dispersion-X-ray luminosity relations for clusters of galaxies. Abell 400 is interesting in this regard, since both its X-ray luminosity and its velocity dispersion are quite small. Such objects are particularly important in determining the slope of the velocity dispersion-X-ray luminosity relation. The large microwave decrement observed in A576 was initially interpreted as due to Compton scattering of the microwave background by the X-ray-emitting intracluster gas. White and Silk have presented Einstein X-ray data which indicate that A576 contains too little gas to produce the observed microwave decrement by Compton scattering. The velocity dispersion obtained here for 47 members of this cluster strengthens their conclusion.
    Keywords: ASTRONOMY
    Type: Astronomical Journal; 87; Dec. 198
    Format: text
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  • 2
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    Multiple object spectroscopy - The Medusa spectrograph (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: An instrument has been built to obtain simultaneous spectra of many objects in the field of view of the Steward 90 inch (2.29 m) telescope. Short lengths of fused silica fiber 300 microns in diameter are used to bring the light from galaxy images at the Cassegrain focus into a line along the spectrograph slit. From a single exposure of the cluster Abell 1904, which has a redshift of 20,000 km/s, the redshifts of 26 individual galaxies were determined, each with a precision of 100 km/s. The present device, while already giving a sixfold reduction in the mean telescope time per galaxy, has significant light losses because it is not ideally matched to the telescope. An instrument being designed for the prime focus will transmit light from each object as efficiently as a conventional spectrograph.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 242
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  • 3
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    Fiber optics for astronomical spectroscopy - The Medusa Spectrograph (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: An instrument has been built to obtain simultaneous spectra of 32 objects in the field of view of the Steward Observatory 2.3 m telescope. Short lengths of optical fiber are used to bring light from galaxy images at the focus of the telescope into a line at the spectrograph slit. This multi-fiber aperture plate instrument has been dubbed the Medusa Spectrograph. The Medusa is now producing spectra of about 100 galaxies per clear night. An optimized version of the instrument called the MX Spectrometer is being constructed to record spectra at a higher rate. This new instrument will have remotely positioned fibers under computer control. A Charge Coupled Device will be used as the spectrograph detector to allow sky subtraction, give increased dynamic range and provide more accurate wavelength calibration. Transmission characteristics of some commercial fibers are discussed, and the microlens optics used to match the telescope and the spectrograph to the fibers to avoid focal ratio degradation are described.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
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  • 4
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    A data reduction package for multiple object spectroscopy (1986)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Experience with fiber-optic spectrometers has demonstrated improvements in observing efficiency for clusters of 30 or more objects that must in turn be matched by data reduction capability increases. The Medusa Automatic Reduction System reduces data generated by multiobject spectrometers in the form of two-dimensional images containing 44 to 66 individual spectra, using both software and hardware improvements to efficiently extract the one-dimensional spectra. Attention is given to the ridge-finding algorithm for automatic location of the spectra in the CCD frame. A simultaneous extraction of calibration frames allows an automatic wavelength calibration routine to determine dispersion curves, and both line measurements and cross-correlation techniques are used to determine galaxy redshifts.
    Keywords: ASTRONOMY
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  • 5
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    Scientific investigations in the Gulf of Mexico and Caribbean Sea during the 1974-1975 Calypso cruise, parts 1 and 2 (1975)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The distribution and concentrations of the standing crop of phytoplankton and nutrient salts in the Gulf of Mexico and the Caribbean Sea were investigated to provide ground truth for correlating temperature and chlorophyll-a measurements with observations from NASA U-2 aircraft equipped with specially designed sensors for measuring ocean color phenomena. The physical, chemical, and biological data obtained is summarized. Sampling procedures and methods used for determining plant pigments, species composition of phytoplankton, nutrient salt analysis, and the euphotic zones are described.
    Keywords: OCEANOGRAPHY
    Type: NASA-CR-156688
    Format: application/pdf
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  • 6
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    Multiple object fiber optic spectroscopy (1982)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The Steward Observatory of the University of Arizona employs short optical fiber lengths to bring light from galaxy images at the 2.3 m telescope's focus to a line along a spectrograph slit, thereby obtaining simultaneous spectra of many objects of the field of view. After describing this instrument, attention is given to the development of an improved version through which efficiency gains will be obtained by remotely positioning the fibers under computer control and by correctly matching fiber outputs to the spectrograph optics. A CCD will replace the presently employed image tube and photographic plate detector system, in order to permit sky subtraction, yield increased dynamic range, and provide more accurate wavelength calibration due to the detector's fixed format.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Instrumentation in astronomy IV; Fourth Conference; Mar 08, 1982 - Mar 10, 1982; Tucson, AZ
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  • 7
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    A biological and physical oceanographic remote sensing study aboard the Calypso (1975)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The paper discusses an oceanographic remote sensing program conducted aboard the R/V Calypso in the Gulf of Mexico and the Caribbean Sea to provide information for correlating ocean measurements with remotely sensed observations. Remote sensors on satellites and aircraft are used as operations and experiment planning tools as well as for scientific data acquisition. Emphasis is on providing surface-truth measurements for OCS flights and on investigating the area of the Gulf affected by the outflow of the Mississippi River. The discussion covers the shipboard instrumentation, ocean color scanner data acquisition and results, NOAA/VHRR data analysis approach, and Landsat and APT/ATS as planning tools. The research effort has demonstrated the feasibility of using satellite data as a supportive method to aid an oceanographic research vessel on a near real-time basis.
    Keywords: OCEANOGRAPHY
    Type: International Symposium on Remote Sensing of Environment; Oct 06, 1975 - Oct 10, 1975; Ann Arbor, MI
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  • 8
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    Nulling Data Reduction and On-Sky Performance of the Large Binocular Telescope Interferometer (2016)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The Large Binocular Telescope Interferometer (LBTI) is a versatile instrument designed for high angular resolution and high-contrast infrared imaging (1.5-13 micrometers). In this paper, we focus on the mid-infrared (8-13 micrometers) nulling mode and present its theory of operation, data reduction, and on-sky performance as of the end of the commissioning phase in 2015 March. With an interferometric baseline of 14.4 m, the LBTI nuller is specifically tuned to resolve the habitable zone of nearby main-sequence stars, where warm exozodiacal dust emission peaks. Measuring the exozodi luminosity function of nearby main-sequence stars is a key milestone to prepare for future exo-Earth direct imaging instruments. Thanks to recent progress in wavefront control and phase stabilization, as well as in data reduction techniques, the LBTI demonstrated in 2015 February a calibrated null accuracy of 0.05% over a 3 hr long observing sequence on the bright nearby A3V star Beta Leo. This is equivalent to an exozodiacal disk density of 15-30 zodi for a Sun-like star located at 10 pc, depending on the adopted disk model. This result sets a new record for high-contrast mid-infrared interferometric imaging and opens a new window on the study of planetary systems.
    Keywords: Astrophysics; Astronomy
    Type: GSFC-E-DAA-TN40853 , The Astrophysical Journal (ISSN 0004-637X) (e-ISSN 1538-4357); 824; 2; 66
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