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Takacs, P. Z.

Publications and source records attributed to Takacs, P. Z..

11 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Electroform replication of smooth mirrors from sapphire masters

A sapphire master was used to produce mirrors that exhibit mid-to-high-frequency roughness as low as 3 A. The fabrication procedure and potential applications in X-ray astronomy are discussed. It is shown that foils replicated from flat smooth mandrels should offer at least equivalent HF roughness and significantly lower mid-frequency ripple than those coated with lacquer. A ceramic-surface mandrel could also be expected to last far longer without the need for repolishing than electroless nickel-coated mandrels.

Altkorn, R.↗
NASA NTRS1991

Normal-incidence soft X-ray telescopes

Photos obtained during 5 min of observation time from the flight of a 25-cm-diameter normal-incidence soft-X-ray (63.5 A) telescope on September 11, 1989, are analyzed, and the data are compared to the results expected from tests of the mirror surfaces. These tests cover a range of spatial periods from 25 cm to 1 A. The photos demonstrate a resolution close to the photon shot-noise limit and a reduction in the scattering of the multilayer mirror compared to a single surface for scattering angles above 1 arcmin, corrresponding to surface irregularities with spatial periods below 10 microns. These results are used to predict the possible performance of future telescopes. Sounding rocket observations might be able to reach a resolution around 0.1 arcsec.

Spiller, Eberhard↗
NASA NTRS1979

Magnetosheath effects on cylindrical Langmuir probes

A study of the response of cylindrical Langmuir probes in magnetoplasmas focusing on the relative magnitudes of Larmor radius and sheath size is presented. The approach results in a classification of magnetic field effects which involves the magnetic field strength and plasma parameters of density, temperature, and the applied probe potential. It is shown that a 0.25 G field can have similar effects on the current collection properties of the probe in ionospheric plasma as a 30 kG field would have in a hot, dense laboratory plasma. The data also show: (1) the effects of probe orientation on electron current collection from magnetoplasmas; (2) that these effects can be important even when the electron Larmor radius is larger than the radius of the probe; and (3) that substantial magnetic field effects occur when the probe sheath is comparable to or greater than the Larmor radius.

Szuszczewicz, E. P.↗
NASA NTRS1979

Extreme ultraviolet observations from Voyager 1 encounter with Jupiter

Observations of the optical extreme ultraviolet spectrum of the Jupiter planetary system during the Voyager 1 encounter have revealed previously undetected physical processes of significant proportions. Bright emission lines of S(+2), S(+3), O(+2) indicating an electron temperature of 100,000 K have been identified in preliminary analyses of the Io plasma torus spectrum. Strong auroral atomic and molecular hydrogen emissions have been observed in the polar regions of Jupiter near magnetic field lines that map the torus into the atmosphere of Jupiter. The observed resonance scattering of solar hydrogen Lyman alpha by the atmosphere of Jupiter and the solar occultation experiment suggest a hot thermosphere (greater than or equal to 1000 K) with a large atomic hydrogen abundance. A stellar occultation by Ganymede indicates that its atmosphere is at most an exosphere.

Broadfoot, A. L.↗
NASA NTRS1977

Far ultraviolet atomic and molecular nitrogen emissions in the dayglow

A scanning spectrophotometer was used to observe the far ultraviolet day airglow between 1130 and 1520 A at 4.4-A spectral resolution. Fourteen bands of the N2 Lyman-Birge-Hopfield (LBH) system are clearly resolved and suggest a total LBH system zenith column emission rate of 3810 plus or minus 520 R extrapolated to the subsolar point. A photoelectron flux model (based on recent photoelectron flux measurements and the observed LBH altitude profile) is used to derive the direct and dissociative excitation contributions to the atomic nitrogen emissions. The calculated atomic nitrogen density agrees with other measurements, although it is an order of magnitude greater than previous photochemical model results.

Takacs, P. Z.↗
NASA NTRS1975

A search for molecular hydrogen fluorescence near 100 km

The fluorescence of H2 in the Lyman band system, excited by solar extreme ultraviolet radiation, provides a means for the optical detection of H2 in the upper atmosphere. In particular, the Ly beta line of hydrogen is nearly degenerate with the (6,0) P1 transition, and absorption in this line produces fluorescence in the v-prime = 6 progression, principally at 1265, 1366, 1462 and 1608 A. Absorption by O2 rapidly attenuates the Ly beta from an overhead sun below 100 km and also significantly attenuates the fluorescent radiation. Far-ultraviolet dayglow spectra from 1130 to 1510 A obtained from an Aerobee rocket experiment on 11 December 1972 give an upper limit for any H2 emission which is a factor of 5 higher than expected according to recent hydrogen models.

Feldman, P. D.↗
NASA NTRS1974

Rocket ultraviolet spectrophotometry of Comet Kohoutek /1973f/

On January 5, 1974, the ultraviolet emissions from Comet Kohoutek (1973f) in the spectral range from 1200 to 3200 A were studied with the aid of a rocket carrying two spectrophotometers. In addition to the Lyman alpha line of atomic hydrogen at 1216 A and the (0,0) and (1,1) bands of OH at 3090 and 3142 A, both atomic oxygen (1304 A) and atomic carbon (1657 and 1561 A) were detected.

Feldman, P. D.↗
NASA NTRS1974

Nitric oxide gamma and delta band emission at twilight

Nitric oxide twilight emission above 140 km in the gamma- and delta-bands was observed with a rocket-borne spectrophotometer. The relative intensity of the two band systems indicates that the emission is produced predominantly by the chemiluminescent preassociation of oxygen and nitrogen atoms.

Feldman, P. D.↗