Engineering topics

Carruthers, G. R.

Publications and source records attributed to Carruthers, G. R..

At least 37 records · Page 2

NASA NTRS1981

Electron bombardment charge-coupled device /CCD/ detectors for the vacuum ultraviolet

Development work is underway at Princeton and NRL on electronic-readout imaging detectors for the VUV which are based on electron-bombardment CCD arrays and opaque alkali-halide photocathodes. These detectors provide single-photoelectron detection capability and wide dynamic range combined with almost the maximum possible quantum efficiency (in excess of 50% in the wavelength range below 1300 A). The Princeton work is based on an oblique-focusing electron optical configuration, while the NRL program is based on a Schmidt optical system with opaque photocathode. Results of preliminary tests at Princeton and overall system concepts for the Princeton and NRL cameras are discussed, and applications to possible space astronomy studies are examined.

Lowrance, J. L.↗

NASA NTRS1980

Rocket-ultraviolet imagery of the North America nebula

New ultraviolet imagery of NGC 7000 has been obtained in a sounding-rocket flight with an electrographic Schmidt camera which covers the 1230-2000 A wavelength range and has a higher angular resolution than the Apollo 16 imagery. The integrated brightness of NGC 7000 near 1450 A is unexpectedly high (three times the brightness of HD 199579 as measured by CHB), but as no emission lines were observed with a nebular spectrograph, it is concluded that the radiation observed in the UV image is nearly pure continuum. Comparison with the blue continuum image is not possible, as the latter image has dominant contributions due to night sky background, hydrogen recombination continuum, and possibly unresolved faint stars. It is suggested that the high UV brightness of NGC 7000 is due to the highly efficient dust scattering of stellar radiation.

Carruthers, G. R.↗

NASA NTRS1979

Ultraviolet astronomy instrumentation for sounding rocket and Shuttle/Spacelab missions

The paper deals with an electrographic Schmidt camera for wide-field imaging and objective-spectrographic sky surveys, and with a nebula spectrograph designed to obtain slit spectra of nebulae and other diffuse sources. Each of these ultraviolet astronomy instruments has been successfully used in sounding rocket flights. It is seen that, with some minor modifications, both instruments should be readily adaptable to Spacelab missions.

Carruthers, G. R.↗

NASA NTRS1979

Wide-field electrographic cameras for imagery and spectrography at visual and middle-UV wavelengths

The use of a Kron electrographic detector for wide-field, narrow-band imagery of faint emission nebulosity in the near-UV and visual (3100-6000 A) wavelength interval is described. As an example of the photometric quality of the imagery and of the sensitivity of the instrumentation to diffuse, low-contrast objects, imagery of the Cygnus Loop supernova remnant in the high excitation forbidden line of Ne V 3426 A is presented. In addition, a program to develop electrographic detectors which use cesium telluride photocathodes for broad-band imagery and spectrography in the middle-UV (1650-3100 A) wavelength range is described.

Heckathorn, H. M.↗

NASA NTRS1979

Electrographic instrumentation for ultraviolet imaging and spectrography

The latest results in the NRL program of far-UV electrographic camera development, and application of these cameras to astrophysical and upper-atmospheric investigations, are presented. A new large electrographic Schmidt camera, of 15 cm aperture and f/2 focal ratio, has been successfully used in two sounding rocket flights, one for direct imagery in the 1230-2000 A wavelength range and the second for objective spectrography in the 950-2000 A range, of stars and nebulae in the Cygnus region of the sky. The camera has an 11 deg field of view and better than 30 arcsec resolution (2 A spectral resolution with 600 line/mm objective grating). A nebular spectrograph, based on a microchannel-intensified electrographic Schmidt camera, is the payload of a May 1979 rocket flight. It will reach emission line features as faint as 5 Rayleighs in 100 second exposures in the 1050-2000 A range, with 5 A spectral resolution.

Carruthers, G. R.↗

NASA NTRS1978

Rocket ultraviolet imagery of the Andromeda galaxy

Far-UV electrographic imagery of M31 is presented which was obtained during a sounding-rocket flight with an electrographic Schmidt camera sensitive in the wavelength range from 1230 to 2000 A. The resolution in the imagery is such that 50% of the energy from a point source is confined within a circle 40 arcsec in radius. Two conspicuous features are observed in the UV image of M31: one corresponding to a bright association (NGC 206) in the SW region of the disk and one centered on the galactic nucleus. Indications of the general spiral-arm structure are also evident. Absolute photometry and brightness distributions are obtained for the observed features, and both the central region and NGC 206 are shown to be diffuse sources. It is found that the brightness distribution of the central region is a flat ellipse with its major axis closely aligned with the major axis of the galaxy, which favors a source model consisting of young early-type stars close to the galactic plane and constitutes strong evidence against a nonthermal point source at the galactic center.

Carruthers, G. R.↗

NASA NTRS1978

Sky surveys in the ultraviolet

Instrumentation, results, and future prospects for sky surveys at UV wavelengths inaccessible from the ground are reviewed. Detectors and optical materials, coatings, and systems for UV surveys are discussed, previously performed UV sky surveys are recounted, and some specific results of these surveys are examined. The rationale for UV surveys is explained, and the detectors and instrumentation considered for future UV surveys are described. It is noted that for the wavelength range from 1000 to 2000 A, detectors and instrumentation are already available to provide an all-sky UV survey of moderate resolution (10 to 30 arcsec) and moderate sensitivity (reaching hot stars as faint as 18th visual magnitude in direct imagery and 11th magnitude spectrographically with 2-A resolution).

Carruthers, G. R.↗

NASA NTRS1977

Far-ultraviolet imagery of the Orion Nebula

Two electrographic cameras carried on a sounding rocket have yielded useful-resolution far-ultraviolet (1000-2000 A) imagery of the Orion Nebula. The brightness distribution in the images is consistent with a primary source which is due to scattering of starlight by dust grains, although an emission-line contribution, particularly in the fainter outer regions, is not ruled out. The results are consistent with an albedo of the dust grains that is high in the far-ultraviolet and which increases toward shorter wavelengths below 1230 A.

Carruthers, G. R.↗

NASA NTRS1977

Lyman-alpha observations of Comet West /1975n/

The rate of hydrogen production of Comet West is studied through rocket observation of solar Lyman-alpha radiation resonantly scattered by the escaping hydrogen atoms. Two sets of Lyman-alpha exposure sequences are used to obtain computer-smoothed brightness contour (isophote) maps covering a density range of 100:1. A simple radial outflow model is applied to the contour maps to determine the rate of hydrogen production (3.2 by 10 to the 30th power atoms/sec.) Discrepancies between the observed shape of the outer isophotes and predicted models may be explained by optical depth effects, or by the presence of small pieces of the comet's nucleus distributed along the orbit. Hydrogen, carbon, and oxygen production for Comet West and Comet Kohoutek are compared; differences may be accounted for by variations in the composition or evolution of the two comets.

Opal, C. B.↗

NASA NTRS1977

Far-ultraviolet imagery of the Barnard Loop Nebula

An electrographic Schmidt camera carried on a sounding rocket has yielded far-ultraviolet (1050-2000 A and 1230-2000 A) images of the Barnard Loop Nebula and of the general background in the Orion region due to scattering of ultraviolet starlight by interstellar dust particles. The total intensity in the Barnard Loop region agrees well with OAO-2 measurements, but the discrete Loop structure contributes only some 15% of the total. The measurements are consistent with a relatively high albedo for the dust grains in the far-ultraviolet.

Carruthers, G. R.↗

NASA NTRS1977

Apollo-16 far-ultraviolet spectra in the Large Magellanic Cloud

Spectra in the wavelength ranges from 900 to 1600 A and 1050 to 1600 A of some OB associations in the Large Magellanic Cloud were obtained from the lunar surface by the Apollo-16 far-ultraviolet camera/spectrograph on April 22, 1972. The observed spectral distributions appear consistent with a stellar model having an effective temperature of 30,000 K, reddened by E(B-V) = 0.3, and characterized by the average far-ultraviolet extinction curve of Bless and Savage (1972). However, the absolute intensity of the far-ultraviolet spectrum of the associations NGC 2050 and 2055 seems somewhat too bright in comparison with ground-based photometry.

Carruthers, G. R.↗

NASA NTRS1977

Apollo 16 far-ultraviolet imagery and spectra of the Large Magellanic Cloud

The Large Magellanic Cloud (LMC) was observed with a far-ultraviolet camera/spectrograph (Experiment S-201) from the lunar surface during the Apollo 16 mission. Images were obtained with about 3-arcmin resolution, in the 1050-1600- and 1250-1600-A wavelengths ranges, of nearly the entire LMC. Spectra were also obtained in the 1050-1600- and 900-1600-A ranges with 30-40-A resolution along a strip 0.25 deg wide passing across the LMC. The images and spectra have been scanned with a microdensitometer, and analyses of the data to date are discussed.

Page, T. L.↗

NASA NTRS1976

Far-ultraviolet rocket astronomy program

The launch of sounding rocket 26.056 DG on 29 October 1976 is described and quick-look results from that mission are given. Also further work on data obtained by 13.118 DG, launched 5 December 1975 is reported.

Carruthers, G. R.↗

NASA NTRS1976

Apollo 16 far-ultraviolet imagery and spectra of the Large Magellanic Cloud

The Large Magellanic Cloud was observed by the far ultraviolet camera spectrograph from the lunar surface during the Apollo 16 mission 22 April 1972. Images were obtained with about 3 arc min resolution, in the 1,050 to 1,600 and 1,250 to 1,600 A wavelength ranges, of nearly the entire LMC. Spectra were also obtained in the 1,050 to 1,600 and 900 to 1,600 A ranges along a strip 1/4 deg wide (determined by the instrument's grid collimator) passing across the LMC. The images and spectra have been scanned with a PDS microdensitometer, and isodensity contour plots have been prepared using the Univac 1108 computer.

Page, T.↗

NASA NTRS1976

Far-ultraviolet brightness of nebulae in Cygnus

A far-ultraviolet electrographic Schmidt camera was operated on the lunar surface during the Apollo 16 mission. Among the results obtained were imagery in the 1050-1600-A and 1250-1600-A wavelength ranges of a 20-deg-diameter field in Cygnus containing the Cygnus Loop nebula, the North America nebula (NGC 7000), and the H II region of the O8 star 68 Cygni. The maximum intensity in the Cygnus Loop was 100 R in the 1250-1600-A range and 130 R in the 1050-1600-A range. The maximum brightnesses in the 1250-1600-A range of the 68 Cyg H II region and of NGC 7000 were about 60 and more than 80 R, respectively, but require relatively large corrections for interstellar extinction.

Carruthers, G. R.↗

NASA NTRS1976

Apollo 16 far ultraviolet imagery of the polar auroras, tropical airglow belts, and general airglow

Far-ultraviolet imagery of the earth in the wavelength ranges from 1050 to 1600 A and from 1250 to 1600 A was obtained from the lunar surface during the Apollo 16 mission on Apr. 21, 1972. The images have an angular resolution of about 2 arcmin (230-km linear resolution) and have been quantitatively analyzed to obtain absolute intensities and spatial distributions of the polar auroras (both wavelength ranges), the day and night airglow, and tropical airglow belts (1250-A to 1600-A wavelength range). The observations are consistent with previous results obtained from the OGO-4 spacecraft, but they have also provided details on the spatial distributions of the various emissions over an entire hemisphere at a single time. A general night airglow, at least in the Northern Hemisphere, is indicated.

Carruthers, G. R.↗

NASA NTRS1974

Lyman-alpha imagery of Comet Kohoutek

Electrographic imagery of Comet Kohoutek in the 1100-1500 A wavelength range was obtained from a sounding rocket on Jan. 8, 1974, and from the Skylab space station on 13 occasions between Nov. 26, 1973 and Feb. 2, 1974. These images are predominantly due to Lyman-alpha (1216 A) emission from the hydrogen coma of the comet. The rocket pictures have been calibrated for absolute sensitivity and a hydrogen production rate has been determined. However, the Skylab camera suffered degradation of its sensitivity during the mission, and its absolute sensitivity for each observation can only be estimated by comparison of the comet images with those taken by the rocket camera, with imagery of the geocoronal Lyman-alpha glow, of the moon in reflected Lyman-alpha, and of ultraviolet-bright stars. The rocket and geocoronal comparisons are used to derive a preliminary, qualitative history of the development of the cometary hydrogen coma and the associated hydrogen production rate.

Carruthers, G. R.↗

NASA NTRS1974

Comet Kohoutek - Ultraviolet images and spectrograms

Emissions of atomic oxygen (1304 A), atomic carbon (1657 A), and atomic hydrogen (1216 A) from Comet Kohoutek were observed with ultraviolet cameras carried on a sounding rocket on Jan. 8, 1974. Analysis of the Lyman alpha halo at 1216 A gave an atomic hydrogen production rate of 4.5 x 10 to the 29th atoms per second.

Opal, C. B.↗