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  • INSTRUMENTATION AND PHOTOGRAPHY  (7)
  • MECHANICAL ENGINEERING  (6)
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  • 1
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    Development of lightweight, glass mirror segments for the Large Deployable Reflector (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Accomplishments in the development of lightweight, honeycomb-core, sandwich mirror blanks made of borosilicate and high-silica glasses at the University of Arizona for the Large Deployable Reflector program are described. In this paper, work spanning the last 2 years is reported, highlighting a new mirror blank fabrication technique that permits the fabrication of the honeycomb core integrally with the front and back plates of the blank in a single furnace cycle. Two types of mirror blanks made by this method, an off-axis, aspheric segment and a smaller Vycor circular piece, are described. The fabrication of two off-axis, aspheric mirror segments is also described. Cryogenic test results are included on the test of a 38-cm diameter, lightweight, honeycomb core, sandwich mirror made of Pyrex.
    Keywords: MECHANICAL ENGINEERING
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  • 2
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    Bragg crystal spectrometer for HEAO-B X-ray astronomy experiment (1973)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The X-ray astronomy experiment for the HEAO mission is described. The instrument to be flown on the satellite consists of two Bragg crystal spectrometers designed to make measurements with high spectral resolution in the energy range from 0.1 to 10 keV. No sharp spectroscopic features were detected directly in X-ray astronomy except emission lines in the sun; therefore, the objectives and design criteria of this instrument are based on the theoretical models of the different types of extra solar X-ray sources. From the point of view of instrumental techniques it is convenient to divide these into point or stellar sources, whose radiation is parallel, and diffuse sources, and to consider the possible spectral features in each type.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: ESRO X-Ray Astronomy in the Near Future; p 155-162
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  • 3
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    Steps toward 8m honeycomb mirror blanks. III - 1.8m honeycomb sandwich blanks cast from borosilicate glass (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: The design, fabrication techniques, and equipment used for producing two 1.8-m honeycomb sandwich blanks, eventually leading to production of 8-m blanks, are reported. The procedure employed 85 cast hexagonal tiles at the bottom section, affixed against flotation by SiC bolts. The two plano concave mirrors are 1.83 m thick, weight 500 kg, and are each designed for 19 supports of astatic-lever type. Both blanks are of high quality and with an adequately low bubble content; one is to be figured to high-precision 0.25-arcsecond images, and is to be tested on the Multiple Mirror Telescope. Construction of a spin-casting facility based on the same principle is being planned for test-fabricating spin-cast mirrors on a smaller scale.
    Keywords: MECHANICAL ENGINEERING
    Type: Advanced technology optical telescopes II; September 5, 6, 1983; London
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  • 4
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    Steps toward 8m honeycomb mirrors IV - Some aspects of design and fabrication (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: The tolerances in glass homogeneity, thermal control, and support of the blank, necessary to meet the requirements of telescopes in the best ground-based sites, are defined for a hypothetical 8-m honeycomb mirror spin-casting facility. Homogeneity in expansion coefficient of 10 to the -8th/C and thermal equilibration to 0.1 C are estimated. Laboratory measurements show that both can be met by a ventilated honeycomb of borosilicate or similar glass. Adequate resistance to wind pressure and buffeting can be achieved by an axial support that responds to pressure on the three defining points. Annealing of the blank at the peak cooling rate of 20 C/day will take about six weeks, leading to a temporary stress of 15 kg/sq cm.
    Keywords: MECHANICAL ENGINEERING
    Type: Advanced technology optical telescopes II; September 5, 6, 1983; London
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  • 5
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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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  • 6
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    Thinning and mounting a Texas Instruments 3-phase CCD (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Thin CCDs with precise control of thickness and surface quality allow astronomers to optimize chips for specific applications. A means of mechanically thinning a TI 800 x 800 CCD with an abrasive slurry of aluminum oxide is presented. Using the same techniques, the abrasives can be replaced with a chemical solution to eliminate subsurface damage. A technique of mounting the CCD which retains the high quality surface generated during thinning is also demonstrated. This requires the backside of the chip to be bonded to a glass window which closely matches silicon's thermal expansion properties. Thinned CCDs require backside treatment to enhance blue and UV quantum efficiency. Two methods are discussed which may be effective with this mounting system.
    Keywords: MECHANICAL ENGINEERING
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  • 7
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    A large-area lithium-fluoride Bragg spectrometer for stellar X-ray astronomy (1975)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: A large-area Bragg spectrometer used to search for the Fe XXV X-ray emission lines of Sco X-1 is described. The device has 3400 sq cm of LiF on nine crystal panels aligned perpendicular to the longitudinal axis of the rocket. X rays satisfying the Bragg condition reflect into an array of nine companion proportional counters. A pointing system incorporating a free gyroscope with 2 degrees of freedom assures that target X rays are reflected at the required angle and produces repeated spectral scans of the X-ray continuum, which are later superimposed to correct temporal effects. The instrument is capable of detecting a narrow line flux from Sco X-1 of about .01 photons/sq cm/sec.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Nuclear Instruments and Methods; 126; 1975
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  • 8
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    Steps toward 8 m honeycomb mirror blanks. II - Experiments with waffleplate and honeycomb casting (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A technique for fabricating large low-cost light-weight borosilicate-glass mirrors for ground and space-based astronomy is described. This technique involves the remelting of glass into complex molds for vacuum-formed ceramic fiber and is used to cast in one piece either waffleplate or full honeycomb sandwich blanks. The construction of molds and the cycle for melting and annealing are described in detail. A 1.1-m square blank with a 22.4-cm-thick face and 1.6-cm ribs, 15-cm deep on 15-cm squares, has been cast, and a 1.8-m circular blank of full honeycomb construction is scheduled for production. The casting of blanks of up to 8-m in diameter is anticipated, with densities of 200 kg/sq m (like that of the ST mirror) being typical of casting.
    Keywords: MECHANICAL ENGINEERING
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  • 9
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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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  • 10
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    Faint Object Spectrograph (FOS) calibration (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The Faint Object Spectrograph (FOS) designed for use with The Space Telescope (ST), is currently preparing for instrument assembly, integration, alignment, and calibration. Nearly all optical and detector elements have been completed and calibrated, and selection of flight detectors and all but a few optical elements has been made. Calibration results for the flight detectors and optics are presented, and plans for forthcoming system calibration are briefly described.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Instrumentation in astronomy IV; Fourth Conference; Mar 08, 1982 - Mar 10, 1982; Tucson, AZ
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