Engineering topics
Publications and source records attributed to Ocallaghan, F. G..
Instrument efficient, lightweight, and stable. Fourier-transform spectrometer configuration uses electronic, instead of mechanical, scanning. Configuration insensitive to vibration-induced sampling errors introduced into mechanically scanned systems.
Remote sensing, high resolution FTS instruments often contain three primary optical subsystems: Fore-Optics, Interferometer Optics, and Post, or Detector Optics. We discuss the alignment of a double-pass FTS containing a cat's-eye retro-reflector. Also, the alignment of fore-optics containing confocal paraboloids with a reflecting field stop which relays a field image onto a camera is discussed.
An objective-prism stellar spectrograph of 15-cm aperture was flown on all three Skylab missions. The wavelength region from 1300 A to 5000 A was covered by a special optical system containing a combination of reflecting telescope optics, a CaF2 objective prism, and an achromatized field-corrector lens system of CaF2 and LiF. Observations of 188 star fields, each covering 4.0 x 5.0 deg of arc, were conducted at the Skylab antisolar airlock with the aid of an articulated mirror system which allowed acquisition within a 30 by 360 deg band of the sky.
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Objective-prism spectra at ultraviolet wavelengths extending to 1300 A were photographed during the three Skylab missions in a survey covering 9 percent of the sky. Several spectral features, notably resonance lines of C IV and Si IV, show striking variations with stellar temperature and luminosity. Marked P Cygni profiles in C IV and Si IV, indicative of significant outflow of mass, appear in the spectra of all stars with bolometric magnitude brighter than -8.4.
Ultraviolet stellar spectra in the wavelength region from 130 to 500 nm were photographed during the three manned Skylab missions using a 15-cm-aperture objective-prism telescope mounted on the antisolar scientific airlock. Data at wavelengths of 200 nm or shorter were obtained for 1400 stars in 166 fields. Approximately 300 stars show absorption lines of Si IV, C IV, or C II in which the strengths and profiles show striking variations with stellar temperature and luminosity. Numerous weak lines are also observed in supergiant stars, shell stars, peculiar A stars, and Wolf-Rayet stars. Observations of comet Kohoutek show interesting variations in the strength of the OH 3090 A band.
Folded all-reflecting Schmidt camera UV image converter system for space astronomy applications, discussing pressure sensitivity effects on UV direct recording emulsion