George R. Carruthers

Rocket observation of interstellar molecular hydrogen

Interstellar molecular H Lyman resonance-absorption bands in far UV spectrum using rocket observation

Apollo 16 far-ultraviolet camera/spectrograph - Earth observations.

A far-ultraviolet camera/spectograph experiment was operated on the lunar surface during the Apollo 16 mission. Among the data obtained were images and spectra of the terrestrial atmosphere and geocorona in the wavelength range below 1600 angstroms. These gave the spatial distributions and relative intensities of emissions due to atomic hydrogen, atomic oxygen, molecular nitrogen, and other species—some observed spectrographically for the first time.

DETECTION OF LYMAN-

A rocket-borne photometer has detected far ultraviolet night glow radiations that are identified as Lyman-β (HI 1026 angstroms), and the helium lines at 304 or 584 angstroms, or at both. At an altitude of 227 kilometers the measured intensity for Lyman-β was about 10 rayleighs. The discrimination characteristics of the broad-band helium radiation filter give helium line intensities, at 227 kilometers, of 4.8 and 12 rayleighs, respectively, pending identification of the wavelength of the radiation as 304 or 584 angstroms. These ultraviolet radiations appear sufficient to maintain the night E and F1 regions of the ionosphere.

beta

Emissions of atomic oxygen (1304 angstroms), atomic carbon (1657 angstroms), and atomic hydrogen (1216 angstroms) from Comet Kohoutek were observed with ultraviolet cameras carried on a sounding rocket on 8 January 1974. Analysis of the Lyman alpha halo at 1216 angstroms gave an atomic hydrogen production rate of 4.5 x 1029 atoms per second.

AND HELIUM RESONANCE RADIATION IN THE NIGHT SKY.

A far-ultraviolet camera/speqtrograph experiment was designed and constructed for studies of the terrestrial upper atmosphere and geocorona, the interplanetary medium, and celestial objects from the lunar surface. The experiment was successfully operated during the Apollo 16 mission 21-23 April 1972. Discussed are the design and operating principles of the instrument, the actual events and operations during the Apollo 16 mission, and also anomalies encountered and suggested improvements for future experiments of this type. This experiment demonstrated the utility of the electronographic technique in space astronomy, as well as the great potential of the lunar surface as a base for astronomical observations.

Comet Kohoutek: Ultraviolet Images and Spectrograms

During NRLs Far Ultraviolet Cameras experiemnt on STS-39, four images of the giant reflection nebula encompassing the Upper Scorpius subgroup of the Sco OB2 association were obtained in two ultraviolet bandpasses with lambda(sub eff) = 1362 A and 1769 A. From these images and IUE and TD-1 stellar spectra, the ratio of nebular to stellar flux was calculated. The ratio ranged from 0.577 to 0.921 at 1362 A and 0.681 to 0.916 at 1769 A with the spread in the ratio arising mainly from uncertainties in the sky background. In order to analyze these images, a model utilizing Monte Carlo techniques to describe radiative transfer in a spherical nebula with asymmetrically distributed stars was developed by elaborating on previous work by Witt. This model was used to determine the range of albedos reproducing the observed nebular-to-stellar flux ratios while allowing the scattering phase function asymmetry to vary between 0.0 and 0.8. The resulting albedos were 0.47-0.70 at 1362 A and 0.55-0.72 at 1769 A.

Apollo 16 Far-Ultraviolet Camera/Spectrograph: Instrument and Operations

A series of magnetically focused, electronographic image converters has been developed for use in far-uv photography and spectroscopy. The use of internal reflecting optics has enabled full advantage to be taken of the very high quantum yields of front-surface alkali halide photocathodes, resulting in over-all detection efficiencies a factor of 10 to 30 higher than similar systems using SC-5 film. An all-reflecting objective spectrograph using this system with Schwarzchild optics has been constructed for obtaining stellar spectra in the 1000-1400-A wavelength range, as well as a similar system based on Schmidt type optics for stellar spectroscopy in the 1230-2000-A wavelength range. Also, smaller Schmidt type instruments have been developed for direct stellar photography in the far uv.

The far-ultraviolet dust albedo in the Upper Scorpius subgroup of the Scorpius OB2 association

Semitransparent photocathodes consisting of vacuum-deposited layers of CsI on electroformed nickel meshes with 40 and 60 lines/mm spacing have been investigated for applications in vacuum-ultraviolet electronic imaging devices. These photocathodes are found to have about half the quantum yield of an opaque CsI photocathode, but a factor of 2 to 3 greater quantum yield than a conventional semitransparent CsI photocathode. The limitations of window materials on short-wavelength spectral response, and their disadvantages in an energetic charged-particle environment, are eliminated. Unlike conventional opaque photocathodes, the mesh photocathodes can be used interchangeably with conventional semitransparent photocathodes in a wide variety of electronic imaging devices. Tests of mesh photocathodes in laboratory electrographic cameras indicate that best results for most applications are obtained if the output electron image has a somewhat poorer resolution than that corresponding to the mesh spacing.

Magnetically Focused Electronographic Image Converters for Space Astronomy Applications

Abstract Electrographic imagery of Comet Kohoutek in the 1100–1500 A wavelength range was obtained from a sounding rocket on January 8, 1974, and from the Skylab space station on 13 occasions between November 26, 1973 and February 2, 1974. These images are predominantly due to Lyman-α (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 sensiti vity fbservation ofn only be estimated by comparison of the comet images with those taken by the rocket camera, with imagery of the geocoronal Lyman-α glow, of the moon in reflected Lyman-α, 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.

Mesh-based semitransparent photocathodes

Far-ultraviolet photometric data for early type stars in Orion, in the 1050–1180 and 1230–1350 Å wavelength ranges, were obtained in an Aerobee rocket flight on 30 January 1969. The results corrected for interstellar extinction, appear in good agreement with model atmospheres in the case of main-sequence stars. Bright giant and supergiant stars, however, appear to be up to one magnitude fainter than main-sequence stars of similar spectral class in the 1050–1180 Å range.The present results indicate that the detectors used in a previous flight were lower in sensitivity than was thought, so the results from that flight have been corrected using the present data for stars in common with the previous flight.The far-ultraviolet extinction law for θ Orionis is shown to be abnormal, with the observed extinction far less than predicted on the basis of ultraviolet extinction measurements of other stars, and the observedE(B-V).