Engineering Papers⌕ Search

Engineering topics

Title, A. M.

Publications and source records attributed to Title, A. M..

47 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Recent advances in birefringent filters

In the past several years, important developments have been made in the construction and theory of birefringent filters. Tunable filters that operate from 4500 to 7000 A with full widths at half maximum of 0.05 A and maximum transmissions of almost 20 percent have been constructed. Inexpensive large-aperture (at least 15 cm) achromatic waveplates have been fabricated which allow full use of resolution-solid angle products that are 100 times that of Fabry-Perots and 10,000 times that of grating systems.

Title, A. M.↗
NASA NTRS1975

Total reduction of distorted echelle spectrograms - An automatic procedure

A total reduction procedure, notable for its use of a computer-controlled microdensitometer for semi-automatically tracing curved spectra, is applied to distorted high-dispersion echelle spectra recorded by an image tube. Microdensitometer specifications are presented and the FORTRAN, TRACEN and SPOTS programs are outlined. The intensity spectrum of the photographic or electrographic plate is plotted on a graphic display. The time requirements are discussed in detail.

Peterson, R. C.↗
NASA NTRS1975

Measurements of solar magnetic fields by Fourier transform techniques. I - Unsaturated lines

If the basic profile shapes of the normal Zeeman triplet do not have zeros in their Fourier transform, the magnetic field splitting can be determined independent of the profile shape. When the ratio of the splitting of the components is greater than the intrinsic FWHM of the component profiles, the magnetic splitting can be determined with significantly greater accuracy than the measurement accuracy of the original profile. For Gaussian shaped components and a ratio of magnetic splitting to FWHM of 1.5, the noise reduction factor is 25.

Title, A. M.↗
NASA NTRS1974

Drift in interference filters. I

Studies of narrow-band interference filters have shown that two mechanisms exist that cause drift to shorter wavelengths. One is dependent on the thermal history of the filter, and the other depends on the radiation history. The present paper presents experimental results on thermal effects; and it is shown that by a proper bake cycle, ZnS-cryolite filters are stable for years if stored at less than 38 C.

Title, A. M.↗
NASA NTRS1974

Drift in interference filters. II - Radiation effects

Studies of peak transmission drift in narrow-band interference filters have shown that there exist two mechanisms that cause drift toward shorter wavelengths. One is dependent on the thermal history of the filter and is discussed in Part 1 of this paper. The other is dependent on the exposure of the filter to radiation. For ZnS-cryolite filters of particular design, it is experimentally demonstrated that the filters are most sensitive to radiation in a 100-A band centered at approximately 3900 A. The drift rate in the focal plane of an f/20 solar image is approximately 3 A/100 hr of exposure. Further, it is also shown by model calculations that the observed radiation-induced drift is consistent with the hypothesis that the optical thickness of ZnS decreases in proportion to the radiant energy absorbed.

Title, A. M.↗
NASA NTRS1974

The spectra spectroheliograph system, section 1

A system capable of producing maps of the magnetic field straight from spectra was created. The theory of the extraction of magnetic field information by Fourier transform techniques is discussed. Contour maps of a high gradient magnetic field region are presented.

Title, A. M.↗
NASA NTRS1974

Operators manual for the magnetograph program (section 2)

This manual for use of the magnetograph program describes: (1) black box use of the programs; (2) the magtape data formats used; (3) the adjustable control parameters in the program; and (4) the algorithms. With no adjustments on the control parameters this program may be used purely as a black box. For optimal use, however, the control parameters may be varied. The magtape data formats are of use in adopting other programs to look at raw data or final magnetograph data.

November, L.↗
NASA NTRS1974

Operators manual for microdensitometer control program densitometer model PDS-1010G (modified). Program trace version 3B (section 3)

The PDS-1010G microdensitometer is run under the control of a PDP-11 program called TRACE. This program gives the operator vary flexible control over the machine functions. Most commands are passed to the computer through either the Tektronix 4010 terminal or the teletype, as selected by the position of the LOCAL/LINE rocker switch above the 4010 keyboard. (LINE places the 4010 in control; LOCAL transfers control to the teletype. In general, the teletype is used when the operator desires a permanent record of the operator-computer dialogue.) A small number of control functions are requested by setting switches on the computer front panel.

Title, A. M.↗
NASA NTRS1971

Fabry-Perot interferometers as narrow band optical filters.

We have constructed solid Fabry-Perot narrow-band filters that can be used in systems having one arc second or better resolution. Our filters operate at H-alpha, have a three-inch aperture, and typical transmission of 70 per cent. However, the same technology can be applied to construction of filters as narrow as 0.05 A at any wavelength from 4200 to 11000 A.

Title, A. M.↗
NASA NTRS1971

Spectra-spectroheliograph observations.

This paper describes a photographic technique for recording solar spectra. The technique, which we call spectra-spectroheliography, requires the same amount of observing time as conventional spectroheliography but yields much more information. Data reduction techniques have been developed to use this information for the construction of spectroheliograms and other contour maps. Parameters investigated by this method include the vector magnetic field, line-of-sight velocity, continuum intensity, and line strength. Results indicate (1) good correlation between bright regions in spectroheliograms and small vertical magnetic fields; (2) poorer correlation between larger magnetic fields and bright regions; (3) a feature in the continuum resembling a pore but having no vertical magnetic field; and (4) a gradient in the vertical magnetic field of 12kG/arc sec.

Title, A. M.↗