Engineering Papers⌕ Search

Engineering topics

Feldman, P. D.

Publications and source records attributed to Feldman, P. D..

At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Electron impact excitation of the Meinel band system of N2/+/

The emission spectrum of the Meinel band system of N2(+) was obtained in the region between 0.72 and 1.6 micrometers by electron impact excitation of N2. The relative excitation function is presented for the (0, 0) band from 22 to 120 eV. Cross sections of the Meinel bands that fall in this region were measured relative to the (2, 0) Meinel band. The results obtained are in good agreement with previously published values below 1.1 micrometers except for the (0, 0) band which is 30% higher. The electronic transition moment at large internuclear distances is found to agree with theoretical estimates.

Mandelbaum, D.↗
NASA NTRS1976

Far ultraviolet excitation processes in comets

Recent observations of atomic oxygen and carbon in the far ultraviolet spectrum of comet Kohoutek have demonstrated the existence of these atomic species in the cometary coma. However, in order to identify the source of their origin, it is necessary to relate the observed ultraviolet flux to the atomic production rate. Analyses of observed OI wavelength 1304 and CI wavelength 1657 A multiplets have been carried out using high resolution solar spectra. Also examined is the possibility of observing ultraviolet fluorescence from molecules such as CO and H2, as well as resonance scattering either from atomic ions for which there are strong corresponding solar lines (CII) or from atoms for which there is an accidental wavelength coincidence (SI).

Feldman, P. D.↗
NASA NTRS1976

Nitric oxide gamma band emission in an aurora

Emission of the NO gamma (1,0) band at 2150 A has been observed by a rocket-borne spectrophotometer in an IBC II(+) aurora. The nu-prime progression of the gamma-system does not appear in the spectrum. The observed emission rate of the 2150 A feature increases relative to N2(+) first negative band emission with increasing altitude. We suggest radiative recombination of NO(+) ions with electrons as a possible excitation mechanism compatible with the data.

Feldman, P. D.↗
NASA NTRS1975

Multiple detector focal plane array ultraviolet spectrometer for the AMPS laboratory

The possibility of meeting the requirements of the amps spectroscopic instrumentation by using a multi-element focal plane detector array in a conventional spectrograph mount was examined. The requirements of the detector array were determined from the optical design of the spectrometer which in turn depends on the desired level of resolution and sensitivity required. The choice of available detectors and their associated electronics and controls was surveyed, bearing in mind that the data collection rate from this system is so great that on-board processing and reduction of data are absolutely essential. Finally, parallel developments in instrumentation for imaging in astronomy were examined, both in the ultraviolet (for the Large Space Telescope as well as other rocket and satellite programs) and in the visible, to determine what progress in that area can have direct bearing on atmospheric spectroscopy.

Feldman, P. D.↗
NASA NTRS1975

Low-resolution ultraviolet spectroscopy of several hot stars observed from Apollo 17

Low-resolution ultraviolet spectra were obtained for six early-type stars in 1972 December, using an Ebert spectrometer mounted in the service module of the Apollo 17 spacecraft. The spectrometer scanned from 1180 A to 1680 A, with a speed that varied with wavelength according to a program chosen for lunar studies. Spectral resolution was 11 A. The ultraviolet absolute calibration of the instrument was determined by comparison with National Bureau of Standards calibrated photodiodes, and is believed known to plus or minus 10 percent. The absolute intensities are in good general agreement with the observations of other stars and with the predictions of stellar model-atmosphere calculations.

Henry, R. C.↗
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 NTRS1975

Rocket and spacecraft studies of ultraviolet emissions from astrophysical targets

Rocket and spacecraft far-UV spectral measurements of several astrophysical targets are reviewed. These include observations of Ly-alpha emissions from Arcturus, Apollo-17 far-UV spectrometry of eta UMa and five other stars, Apollo-17 observations of the lunar atmosphere and the diffuse UV background, and far-UV spectral studies of Venus, Jupiter, and Comet Kohoutek. The Arcturus observations indicated a chromosphere with neutral atomic-hydrogen and atomic-oxygen emissions as well as a very weak atomic-carbon line. The planetary studies revealed O I and C I emissions in the Venusian spectrum as well as large Ly-alpha emissions and possible molecular-hydrogen emissions in that of Jupiter. The lunar observations demonstrated that solar protons do not produce an atomic-hydrogen atmosphere on the moon.

Fastie, W. G.↗
NASA NTRS1975

Auroral electrons and the optical emissions of nitrogen

Simultaneous rocket measurements of the auroral electron flux and the optical emissions of N2 give a consistent picture of electron impact excitation in an aurora. The electron data show that the incident auroral electrons are nearly monoenergetic with energy about 25 keV. The overall shape of the observed low-energy electron spectrum is in good agreement with other recent observations and also with recent theoretical models, although there is some disagreement with the models in the value of the power law slope above 20 eV. A discussion of the secondary electron spectrum obtained near apogee shows that a single power law cannot accurately describe the secondary electron spectrum in the energy range from 3 to 85 eV. About 40% of the N2(+) 1NG (0,0) band emission at 3914 A is excited by electrons with energy below 85 eV.

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.↗
NASA NTRS1973

A search for far-ultraviolet emissions from the lunar atmosphere

An ultraviolet spectrometer aboard the Apollo 17 orbiting spacecraft attempted to measure ultraviolet emissions from the lunar atmosphere. The only emissions observed were from a transient atmosphere introduced by the lunar landing engine. The absence of atomic hydrogen implies that solar wind protons are converted to hydrogen molecules at the lunar surface.

Fastie, W. G.↗
NASA NTRS1973

Fluorescence of molecular hydrogen excited by solar extreme-ultraviolet radiation

During trans-earth coast, the Apollo 17 ultraviolet spectrometer was scheduled to make observations of the far ultraviolet background in selected regions of the sky. In the course of one of these observations, the spacecraft fuel cells were routinely purged of excess hydrogen and water vapor. The ultraviolet fluorescence spectrum of the purged molecular hydrogen excited by solar extreme ultraviolet radiation is interpreted by absorption of solar L-beta and L-gamma radiation in the nearly resonant (6, 0) and (11, 0) Lyman bands. The results are deemed significant for ultraviolet spectroscopic investigations of the atmospheres of the moon and planets since Lyman-band fluorescence provides an unambiguous means of identification of molecular hydrogen in upper atmospheres.

Feldman, P. D.↗
NASA NTRS1973

Daytime ion chemistry of N2+.

Rocket measurements of the emission of the (0, 0) first negative band of N2+ at 3914 A in the day airglow have been made between 120 and 300 km. The solar zenith angle at the time of the flight was 60 deg, and the zenith intensity above 120 km was 1.6 kR averaged over both legs of the flight. The data are compared with a model in which charge exchange of N2 with metastable O+(2D) ions is included as an additional source of N2 ionization. Above 240 km this mechanism is dominant over the photoionization of N2 by solar extreme ultraviolet radiation. The derived N2+ density is consistent with the results of rocket-borne mass spectrometric observations.

Feldman, P. D.↗
NASA NTRS1973

Far ultraviolet spectra and altitude profiles of the dawn airglow.

The far ultraviolet spectrum of the dawn airglow was observed with a scanning Ebert spectrophotometer aboard an Aerobee 170 rocket launched from White Sands, New Mexico, on January 25, 1971, at 0727 MST. Altitude profiles were obtained between 100 and 244 km for the brightest spectral features, HI 1216, OI 1304, and OI 1356. The OI 1356 column intensity is used to estimate a 1356 intensity of about 10 R at the unilluminated magnetic conjugate point; this procedure is consistent with recent observations.

Rottman, G. J.↗
NASA NTRS1973

Ultraviolet spectrometer experiment

The ultraviolet spectrometer (UVS) onboard the Apollo 17 orbiting spacecraft was used to measure emissions from the lunar atmosphere. The UVS and calibration are discussed along with the lunar atmosphere observations and lunar albedo measurements.

Fastie, W. G.↗
NASA NTRS1972

Dayglow forbidden O I 6300 and 5577 A lines in the early morning ionosphere.

Data on a developing morning ionosphere have been obtained by rocket measurement of the atomic oxygen red- and green-line airglow emissions and of the composition of the neutral and ionized constituents of the upper atmosphere. The use of tilting-filter photometers for the optical measurements resulted in reliable and accurate height profiles of the airglow intensity from below 100 to 245 km. The roles of the excitation of both O(super 1 D) and O(super 1 S) atoms by the dissociative recombination of O2(+) and electron impact were studied by using the 6300- and 5577-A data in conjunction with the ion composition measurements. The component of photodissociative excitation of O(super 1 D) by solar radiation in the Schumann-Runge continuum of O2 absorption was assessed as being approximately twice that determined for a previous rocket experiment.

Schaeffer, R. C.↗