SEARCH · Engineering Papers
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
General Optical Systems Evaluation Program, GENOPTICS, aids analysis and evaluation of optical systems that employ lenses, mirrors, diffraction gratings and other geometrical surfaces. GENOPTICS uses geometrical ray tracing based on Snell's law.
The applications of the photo-activated, the CCD-addressed, and the variable-grating mode liquid crystal light valves (LCLVs) to optical data processing are described. These applications include image correlation, level slicing, spectral analysis and correlation, bi-spectral image division, and matrix-matrix multiplication.
An extreme ultraviolet (EUV) spectrometer experiment operated successfully during the STS-7 mission in an experiment to measure the global and diurnal variation of the EUV airglow. The spectrometer is an F 3.5 Wadsworth mount with mechanical collimator, a 75 x 75 mm grating, and a bare microchannel plate detector providing a spectral resolution of 7 X FWHM. Read-out of the signal is through discrete channels or resistive anode techniques. The experiment includes a microcomputer, 20 Mbit tape recorder, and a 28V, 40 Ahr silver-zinc battery. It is the first GAS payload to use an opening door. The spectrometer's 0.1 x 4.2 deg field of view is pointed vertically out of the shuttle bay. During the STS-7 flight data were acquired continuously for a period of 5 hours and 37 minutes, providing spectra of the 570 A to 850 A wavelength region of the airglow. Five diurnal cycles of the 584 A emission of neutral helium and the 834 A emission of ionized atomic oxygen were recorded. The experiment also recorded ion events and pressure pulses associated with thruster firings. The experiment is to fly again on Mission 41-F.
Seven gallium doped germanium (Ge:Ga) photoconductive infrared detectors were fabricated and mounted in integrating cavities. In addition, a cold preamplifier package consisting of J230 junction field effect transistors (JFETs) was produced. Tests of the system under low photon background conditions indicated that sensitivity was limited by the Johnson noise of the load resistor. The detectors were mounted in the Ames cooled grating spectrometer, and flown on the Kuiper Airborne Observatory. Good quality astronomical data were obtained during the flight of 7 July 1983.
Photographs from a NASA U-2 airplane flying over nocturnal thunderstorms show frequent lightning activity in the upper part of the cloud. In some cases, unobscured segments of lightning channels 1 km or longer are visible in clear air around and above the cloud. Multiple images of lightning channels indicate multiple discharges in the same channel. Photographs taken through a diffraction grating show that the lightning has a spectrum similar to that observed in the lower troposphere. Lightning spectra obtained with a slitless line-scan spectrometer show strong singly ionized nitrogen emissions at 463.0 and 500.5 nm. Field changes measured with an electric field-change meter correlate with pulses measured with a photocell optical system. Optical signals corresponding to dart leader, return stroke, and continuing current events are readily distinguished in the scattered light emerging from the cloud surface. The variation of light intensity with time in lightning events is consistent with predicted modification of optical lightning signals by clouds. It appears that satellite based optical sensor measurements cannot provide reliable information on current rise times in return strokes. On the other hand, discrimination between cloud-to-ground and intracloud flashes and the counting of ground strokes is possible using the optical pulse pairs which have been identified with leader, return-stroke events in the cloud-to-ground flashes studied.
From the combined data set of glow observations on STS-3, STS-4 and STS-5 some of the properties of the Shuttle glow were observed. Comparison of the STS-3 (240 km) and STS-5 (305 km) photographs show that the intensity of the glow is about a factor of 3.5 brighter on the low altitude (STS-3) flight. The orbiter was purposely rotated about the x axis in an experiment on STS-5 to observe the dependence of the intensity on the angle of incidence between the spacecraft surface normal and the velocity vector. For a relatively large angle between the velocity vector and the surface normal there is an appreciable glow, provided the surface is not shadowed by some other spacecraft structure. As the angle becomes less the glow intensifies. The grating experiments (STS-4 photography only, STS-5 image intensifier photography) provided a preliminary low resolution spectra of the spacecraft glow. Accurate wavelength calibrations of the STS-5 instrument permitted measuring of the spectrum and intensity of the earth's airglow. Previously cited in STAR as N83-30509
Doppler broadening of the 8691, 8212, and 1200-A multiplet lines of N I is investigated experimentally, and its implications for the interpretation of the earth's 1200-A UV dayglow are considered. A regulated 100-eV, 1-mA electron beam is passed through N2 at 300 K and about 0.0005 torr flowing through a collision chamber within a UHV system, and the radiation emitted is observed with a temperature-stabilized short-focal length monochromator with a bandpass of 0.2 A in the IR and an effective UV resolution (in second-order operation with a 3600-groove/mm plane grating) of about 0.04 A. Both the IR and VUV lines are found to be broadened to about 25 times the thermal Doppler linewidth, with the IR transitions accounting for more than half of the total N(4P) cross section at 100 eV. The kinetic energy of the N(4P) atoms produced by dissociative excitation is such that their 1200-A resonance radiation (2p2 3s4P - 2p3 4SO) would be optically thin in the upper atmosphere, contrary to what has been observed. A need to revise some aspects of current UV-dayglow models is identified.
NGC 7027 was observed with a multichannel grating spectrometer from 5.2 to 7.5 microns at a spectral resolving power of 120-200. Two new dust emission features are resolved at 5.62 and 6.95 microns, and for the first time the Ni II fine-structure line at 6.64 microns is detected. It is shown that a single molecular dust constituent might account for six of the nine observed dust features between 2 and 14 microns. The strength of the Ni II line indicates either that Ni is not depleted in the neutral gas, or that the line is formed at high density.
A photographic-dispersion image of the earth limb airglow obtained during STS-5 using an S-20-photocathode image intensifier and a 300-line/mm holographic grating on the 55-mm f/1.4 objective lens of a standard 35-mm camera is presented and analyzed. The camera/intensifier spectral response and image wavelength are calibrated using a secondary standard continuum source and a mercury-lamp-illuminated slit, respectively. Features identified in the low-resolution spectrally dispersed image include the 7600-A 02 airglow (estimated intensity 200-300 kR), the 5577-A atomic-oxygen emission (4-6 kR), and the 7300-A Meinel-band OH continuum. The intensity of the O2 feature is in agreement with that found in oblique-rocket measurements by Megill et al. (1970).
Image-intensified photographic observations of vehicle glow from the STS-8 Space Shuttle mission are discussed. An objective grating spectrometer preceding a camera was used to measure the intensity of the glow. It is found that glow intensity is dependent on the nature of the vehicle material. With limited resolution of the objective spectrum vehicle glow appeared as a continuum emission. The intensity of the glow from the tail of the vehicle became detectable at 4600 A and increased toward the red. Between 7000 and 8000 A, a slight decrease in the glow intensity is inferred. The absolute intensity of the obliquely viewed tail glow was measured at 450 Rayleighs per Angstrom at 7000 A and 1 MR in the range within the transmission band of the image intensifier camera. The spectral distribution is found to be in agreement with measurements taken from the atmospheric explorer satellite. Samples of the photographic data are provided.
Surface fluctuation spectroscopy is a dynamic light scattering technique which involves the detection of thermal fluctuations (capillary waves) that cover every liquid interface. The advantages of this technique over conventional mechanical methods are discussed. The signal resolution and precision are improved by using a grating heterodyne technique coupled with a digital correlator. Detailed calculations showed that, for the measured power spectrum (the Fourier transform of the correlation function) to take the Lorentzian shape, it is necessary that certain optical conditions be met. These conditions are demonstrated with experimental data collected for ethanol at the ambient temperature as a function of the wave number. Once the optical parameters are adjusted correctly, the experimental results show excellent agreement with the literature values. It is also demonstrated that, using microcomputer technology, the entire system can be automated.
The atmospheric emissions photometric imaging experiment was flown on Spacelab 1 to study faint natural and artificial atmospheric emission phenomena. The instrument imaged optical emission in the region 2000 to 7500 angstroms with a television system consisting of two optical channels, one wide-angle and one telephoto. A third optical channel imaged onto the photocathode of a microchannel plate photomultiplier tube that has 100 discrete anodes. A hand-held image intensifier camera with an objective grating permitted spectral analysis of the earth's airglow and the Shuttle glow. Preliminary data show magnesium ion emission features in the lower ionosphere as well as the spacecraft glow spectrum.
From the combined data set of glow observations on STS-3, STS-4 and STS-5 some of the properties of the Shuttle glow were observed. Comparison of the STS-3 (240 km) and STS-5 (305 km) photographs show that the intensity of the glow is about a factor of 3.5 brighter on the low altitude (STS-3) flight. The orbiter was purposely rotated about the x axis in an experiment on STS-5 to observe the dependence of the intensity on the angle of incidence between the spacecraft surface normal and the velocity vector. For a relatively large angle between the velocity vector and the surface normal there is an appreciable glow, provided the surface is not shadowed by some other spacecraft structure. As the angle becomes less the glow intensifies. The grating experiments (STS-4 photography only, STS-5 image intensifier photography) provided a preliminary low resolution spectra of the spacecraft glow. Accurate wavelength calibrations of the STS-5 instrument permitted measuring of the spectrum and intensity of the earth's airglow.
Recent atomic data have been used to analyze a solar flare spectrum obtained with the Goddard Space Flight Center's grating spectrometer on the OSO-5 satellite. There exist in the wavelength region 90-200 A strong lines from each of the ions Fe XVIII-Fe XXIV. The Fe XXI lines can be used as an electron density diagnostic for the 10 to the 7th K plasma. From an analysis of a particular flare, a steep positive slope in the emission measure between 10 to the 6.5th and 10 to the 7.2th K and an electron density of about 4 x 10 to the 11th per cu cm at 10 to the 7th K is found. The need is emphasized for high spectral and spatial resolution observations of solar flares in this wavelength region, which has to date been largely neglected.
Airborne spectrometer combines technologies of television imaging and spectroscopy to produce data for geophysical surveys, agricultural assessments, forest and land management, and exploration for oil and minerals. Designed for Small Size, infrared imaging spectrometer uses folded telescope and passes input and output of its monochromator through hole in monochromator grating. Instrument permits analysis of terrain at many infrared wavelengths.
Experimental analyses were performed for determination of in plane deformations and shear strains in unidirectional and quasi-isotropic graphite-epoxy beams. Forty-eight ply beams were subjected to 5 point and 3 point flexure. Whole field measurements were recorded at load levels from about 20% to more than 90% of failure loads. Contour maps of U and W displacement fields were obtained by moire interferometry, using reference gratings of 2400 lines/mm. Clearly defined fringes with fringe orders exceeding 1000 were obtained. Whole field contour maps of shear strains were obtained by a method developed for these tests. Various anomalous effects were detected in the displacement fields. Their analysis indicated excess shear strains in resin rich zones in regions of shear tractions; free edge shear strains in quasi-isotropic specimens in regions of normal stresses; and shear stresses associated with cyclic shear compliances of quasi-isotropic plies in regions of shear tractions. Their contributions could occur independently or in superposition. Qualitative analyses addressed questions of relaxation; influence of contact stress distribution; specimen failure; effect of specimen overhang; nonlinearity; and qualities of 5 and 3 point flexure tests.
X-ray analyses were made of the hydroxides of the bivalent metals. The freshly pptd. hydroxide is usually in the alpha-form, which on standing is converted to another form or other forms. The alpha and c grating dimensions of the alpha-form and the C6-type of Co, Zn, C, Co-Zn and Ni-Zn hydroxides are tabulated. Ni hydroxide does not exhibit an alpha-form. The alpha-Co(OH)2, the blue form, is stabilized by sugar or by the higher alcohols: these compounds do not stabilize alpha-Zn(OH)2.
An oblique focus intensified charge coupled device (ICCD) was constructed and operated in a vacuum system. Special gratings were obtained and an optical system set up to try to model a candidate UV spectrometer (Milieu Interstellaire et Intergalactique-MISIG), and to produce small enough images to test the theoretical subpixel resolution capability of the ICCD system. The efforts were only partly successful. Based on the results, a similar detector was built and flown successfully on a Princeton rocket program.