Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “monochromators”

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.

At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Collecting efficiency of a cylindrical mirror electron energy analyzer with preretarding lens

The electron collecting efficiency of a cylindrical mirror energy analyzer incorporating retardation of the electrons prior to analysis has been determined over the range 0 to 30 eV by two methods. The first method requires the use of a vacuum ultraviolet monochromator to produce monoenergetic electrons of different energies; the second method involves measuring the energy-brightness relationship of the retarding optics and should be applicable to any deflection analyzer with pre-retarding optics. The results of the two methods are compared and the limitations of the latter method are discussed.

Gardner, J. L.↗
NASA NTRS1974

Extraterrestrial solar spectrum, 3000-6100 A at 1-A intervals

Standard values of the solar constant and extraterrestrial solar spectrum are reviewed. In the visible and near UV, this listing of average irradiance over 100-A bandwidths at 50-A intervals was found to be inadequate for many applications. A more detailed spectrum obtained from solar scans with a Perkin-Elmer, Model 112 monochromator was found to give sufficient detail. A normalization program was developed to make the Perkin-Elmer curve agree with the standard curve. Values of extraterrestrial solar spectral irradiance at 1-A intervals in the range 3000-6100 A have been derived. The results are presented in tabular form and as spectral charts.

Thekaekara, M. P.↗
NASA NTRS1974

The effects of a visual fidelity criterion on the encoding of images

Shannon's rate-distortion function provides a potentially useful lower bound against which to compare the rate-versus-distortion performance of practical encoding-transmission systems. However, this bound is not applicable unless one can arrive at a numerically-valued measure of distortion which is in reasonable correspondence with the subjective evaluation of the observer or interpreter. We have attempted to investigate this choice of distortion measure for monochrome still images. This investigation has considered a class of distortion measures for which it is possible to simulate the optimum (in a rate-distortion sense) encoding. Such simulation was performed at a fixed rate for various measures in the class and the results compared subjectively by observers. For several choices of transmission rate and original images, one distortion measure was fairly consistently rated as yielding the most satisfactory appearing encoded images.

Mannos, J. L.↗
NASA NTRS1974

Relative cross section and depolarization of NOCl

A standard photon counting technique and an argon-ion laser with 4545, 4579, 4727, 4765, 4880, 4965, 5017 and 5145-A lasing lines, providing a measurable Raman spectrum from NOCl, were used in the measurement of the Raman scattering cross section of NOCl at a Raman shift of 334.4 plus or minus 1.6/cm in relation to the N2 Raman cross section. A polarization analyzer and a quartz wedge were placed in front of the entrance slit of the double monochromator for depolarization measurements. Diagrams are plotted to show the scattering cross section and depolarization measurement results.

Hoell, J. M.↗
NASA NTRS1975

Human factors considerations for the use of color in display systems

Identified and assessed are those human factor considerations impacting an operator's ability to perform when information is displayed in color as contrasted to monochrome (black and white only). The findings provide valuable guidelines for the assessment of the advantages (and disadvantages) of using a color display system. The use of color provides an additional sensory channel (color perception) which is not available with black and white. The degree to which one can exploit the use of this channel is highly dependent on available display technology, mission information display requirements, and acceptable operational modes.

Demars, S. A.↗
NASA NTRS1974

Ion and electron temperatures in the SUMMA mirror device by emission spectroscopy

Ion and electron temperatures, and ion drift were measured in a superconducting magnetic mirror apparatus by observing the Doppler-broadened charge-exchange component of the 667.8 and 587.6 nanometer He lines in He plasma, and the H sub alpha and H sub beta lines in H2 plasma. The second moment of the line profiles was used as the parameter for determining ion temperature. Corrections for magnetic splitting, fine structure, monochromator slit function, and variation in charge-exchange cross section with energy are included. Electron temperatures were measured by the line ratio method for the corona model, and correlations of ion and electron temperatures with plasma parameters are presented.

Patch, R. W.↗
NASA NTRS1974

Study of time-lapse processing for dynamic hydrologic conditions

The usefulness of dynamic display techniques in exploiting the repetitive nature of ERTS imagery was investigated. A specially designed Electronic Satellite Image Analysis Console (ESIAC) was developed and employed to process data for seven ERTS principal investigators studying dynamic hydrological conditions for diverse applications. These applications include measurement of snowfield extent and sediment plumes from estuary discharge, Playa Lake inventory, and monitoring of phreatophyte and other vegetation changes. The ESIAC provides facilities for storing registered image sequences in a magnetic video disc memory for subsequent recall, enhancement, and animated display in monochrome or color. The most unique feature of the system is the capability to time lapse the imagery and analytic displays of the imagery. Data products included quantitative measurements of distances and areas, binary thematic maps based on monospectral or multispectral decisions, radiance profiles, and movie loops. Applications of animation for uses other than creating time-lapse sequences are identified. Input to the ESIAC can be either digital or via photographic transparencies.

Serebreny, S. M.↗
NASA NTRS1975

Study of efficient video compression algorithms for space shuttle applications

Results are presented of a study on video data compression techniques applicable to space flight communication. This study is directed towards monochrome (black and white) picture communication with special emphasis on feasibility of hardware implementation. The primary factors for such a communication system in space flight application are: picture quality, system reliability, power comsumption, and hardware weight. In terms of hardware implementation, these are directly related to hardware complexity, effectiveness of the hardware algorithm, immunity of the source code to channel noise, and data transmission rate (or transmission bandwidth). A system is recommended, and its hardware requirement summarized. Simulations of the study were performed on the improved LIM video controller which is computer-controlled by the META-4 CPU.

Poo, Z.↗
NASA NTRS1975

The total and spectral solar irradiance and its possible variations

The present status of knowledge of the total and spectral irradiance of the sun is briefly reviewed. Currently accepted values of the solar constant and the extraterrestrial solar spectral irradiance are presented along with a discussion of how they were derived. Data on the variability of the solar constant are shown to be conflicting and inconclusive. Some of the alleged sun-weather relationships are cited in support of the need of knowing more precisely the variations in total and spectral solar irradiance. An overview of a solar monitoring program is discussed, with special emphasis on the Solar Energy Monitor in Space experiment which was proposed for several spacecraft missions. It is a combination of a solar constant detector and a prism monochromator. The determination of absolute values and the possible variations of the total and spectral solar irradiance, from measurements outside of the atmosphere is discussed.

Thekaekara, M. P.↗
NASA NTRS1975

Carbon dioxide sensor

Analytical techniques for measuring CO2 were evaluated and rated for use with the advanced extravehicular mobility unit. An infrared absorption concept using a dual-wavelength monochromator was selected for investigation. A breadboard carbon dioxide sensor (CDS) was assembled and tested. The CDS performance showed the capability of measuring CO2 over the range of 0 to 4.0 kPa (0 to 30 mmHg) P sub (CO2). The volume and weight of a flight configured CDS should be acceptable. It is recommended that development continue to complete the design of a flight prototype.

Source record↗
NASA NTRS1974

O/1 D/ production in ozone photolysis near 3100 A

Relative quantum yields of O(1 D) production in ozone photolysis from 2750 to 3340 A have been determined in the gas phase at -40 C. The O(1 D) was monitored by means of its reaction with isobutane to form isobutyl alcohol. The light source was a high pressure mercury lamp combined with a monochromator, with a bandwidth of 16 A. The results show a constant O(1 D) production below 3000 A, which is taken as unity on the basis of previous work. There is a very sharp fall-off in O(1 D) production which is centered at 3080 A. At 3130 A, O(1 D) production is not greater than 0.1.

Lin, C.-L.↗
NASA NTRS1974

Ion and electron temperatures in the SUMMA mirror device by emission spectroscopy

Ion temperatures were obtained in the SUMMA mirror device by observing the Doppler-broadened charge-exchange component of the 667.8and 587.6-nm He lines in He plasma and the H alpha and H beta lines in H2 plasma. The second moment of the line profiles was used as the parameter to determine ion temperature. Corrections for magnetic splitting, fine structure, monochromator slit function, and variation in charge-exchange cross section with energy are derived and included. Even for constant cross section, no magnetic splitting or fine structure, and infinitely narrow slit function, the line profile is not Gaussian, because the excitation results from a change-exchange process. Comparison is made with temperatures from a neutral particle analyzer.-

Patch, R. W.↗
NASA NTRS1975

Absolute radiometric calibration of detectors between 200-600 A

A description is given of the experimental methods used in the calibration procedure, taking into account the source of radiant energy, the monochromator, the absolute standard detector, and the transfer standards. The experimental apparatus is discussed. A graph showing the effect of beam motion on the detected signal is presented and a block diagram of the calibration electronic system is provided.

Saloman, E. B.↗
NASA NTRS1975

Collecting efficiency of a cylindrical mirror electron energy analyzer with pre-retarding lens

The electron collecting efficiency of a cylindrical mirror energy analyzer incorporating retardation of the electrons prior to analysis has been determined over the range 0 to 30 eV by two methods. The first method requires the use of a vacuum ultraviolet monochromator to produce monoenergetic electrons of different energies; the second method involves measuring the energy-brightness relationship of the retarding optics and should be applicable to any deflection analyzer with pre-retarding optics. The results of the two methods are compared and the limitations of the latter method are discussed.

Gardner, J. L.↗
NASA NTRS1975

Unfolding first and second order diffracted radiation when using synchrotron radiation sources - A technique

A technique is presented of using a single calibrated XUV detector for radiometric measurements of synchrotron radiation after the radiation passes through a monochromator that produces a mixture of first- and second-order diffracted radiation. Irradiance measurements are made with the synchrotron source operating at two different energies for the orbiting electrons. The known change in the spectral distribution produced by the electron energy change is used to calculate the flux in both first and second order. The dependence of the precision of these determinations on the two detected currents and on the detector calibration at both first- and second-order wavelengths is calculated. Experimental results using the National Bureau of Standards synchrotron (SURF-I) are presented, and anticipated results for the new NBS electron storage ring (SURF-II) are calculated.

Saloman, E. B.↗
NASA NTRS1975

The Solar Backscatter Ultraviolet and Total Ozone Mapping Spectrometer /SBUV/TOMS/ for Nimbus G

The SBUV/TOMS measures the atmospheric ozone vertical profile and the solar ultraviolet spectrum, and provides a total ozone map by means of a mechanical scan across the Nimbus track. While the SBUV/TOMS instrument has noteworthy design features such as a state-of-the-art double monochromator and fixed optical components on a nonmetallic structure, its most significant characteristic is an optimum system design based on technology proven on the BUV instrument.

Heath, D. F.↗
NASA NTRS1976

Video display synthesizer

Dc command voltages from analog computer can be displayed as four dots and two crosshairs configured to provide illusion of depth via planar or stereo presentations in monochrome or color and if stereo, using dual monitors, single monitor with split screen, or single monitor with color separation.

Grant, C.↗