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Kerr, R. B.

Publications and source records attributed to Kerr, R. B..

10 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Recent observations of the OI 8446 A emission over Millstone Hill

Evening twilight spectra of the OI 8446 A emission were obtained during May and June of 1993 using a single-etalon, pressure scanning, Fabry-Perot interferometer located in the Millstone Hill Optical Facility. The goals of this work are to positively identify the 8446 A emission in the twilight airglow and to determine the intensity decay as a function of solar depression angle. Also, a study of the relative triplet line strengths is performed in hopes of establishing the importance of the primary excitation mechanisms (photoelectron impact or Bowen fluorescence) during the twilight period. Although absent in most of the data, a distinct auroral influence is also found to contribute considerably, on occasion, to the emission over Millstone Hill. The ratio of the combined 8446.26 A and 8446.38 A intensities to the 8446.76 A intensity varies as 0.13 +/- 0.03 per degree of solar depression angle, indicating that secondary excitation mechanisms are becoming increasingly important as evening twilight progresses. Bowen fluorescence is not found to be the primary excitation mechanism at any time during twilight, contributing just a few Rayleighs at most. These observations are an important first step toward a better characterization of highly variable thermospheric oxygen concentrations through ground-based measurements of the OI 8446 A emission.

Lancaster, R. S.↗
NASA NTRS1989

Ground-based measurements of O 1D and the H2O production rate from comets

High spectral resolution 6300.3 A line profiles of Comet Halley are modeled to determine the relative contributions to the emission that can be expected from the distant O 1D daughters produced by photodissociation H2O, CO2, and CO. The results are compared with profiles measured with a single etalon Fabry-Perot interferometer interfaced with a 0.4-m telescopre. To accurately calculate Q O 1D using the 6300.3 A intensity, the line profile must be known. It is shown that the outflow velocity of the parent molecules from the nucleus can be determined using the interferometer profiles.

Kerr, R. B.↗
NASA NTRS1987

Observations of Comet Halley at H-alpha and 6300 A

High spectral resolution measurements of Comet Halley at H-alpha and OD-1 were obtained in March, 1986 using a small aperture telescope with the Fabry-Perot interferometer at the Arecibo Observatory. It is suggested that the highly structured spectral signature observed at H-alpha is due to collimation of atomic hydrogen in the inner hydrogen corona, following photodissociation of parent species, and that the emission is due to resonance fluorescence of solar Lyman-beta radiation. A feature at 6300.8 A accompanying the OD-1 emission at 6300.3 A is attributed to NH2. For a 6-arcmin field of view, a brightness for the OD-1 emission of 260 + or - 50 rayleighs is found for both March 15 and 17.

Kerr, R. B.↗
NASA NTRS1985

High spectral resolution Fabry-Perot interferometer measurements of Comet Halley at H-alpha and 6300 A

A 40.6-cm Newtonian telescope was interfaced to the Fabry-Perot interferometer at the Arecibo Observatory to make high-spectral-resolution measurements of Comet Halley emissions at 6562.72 A (H-alpha) and 6300.3 A (O I). The atomic hydrogen outflow velocity was found to be approximately 7.9 + or - 1.0 km/s. In general, the H-alpha spectra are highly structured, and indicative of a multiple component atomic hydrogen velocity distribution. For O (1D), implied production rates of 6.44 + or - 3.0 x 10 to the 28th/s and 5.66 + or - 2.7 x 10 to the 28th/s were found on March 15 and 17, respectively.

Kerr, R. B.↗
NASA NTRS1984

Global distribution of helium in the upper atmosphere during solar minimum

The annual variations in the concentration of helium in the atmosphere have been measured by open mass spectrometry from onboard the Atmosphere Explorer C (AE-C) satellite. The observations were performed during the solar minimum in 1976 when geomagnetic activity was relatively low. It is shown that the monthly variation in helium number density has a smooth distribution over all latitudes throughout the year. The enhancement of helium over the winter pole (the helium bulge) is found to change slowly as the seasons progress. The progression of winter helium enhancement is given in a series of latitudinal profiles of helium number density for each month of the year. On the basis of the gradual variations in helium concentrations, it is suggested that the global thermospheric wind systems may also change gradually throughout the year.

Cageao, R. P.↗
NASA NTRS1982

Copernicus measurement of the Jovian Lyman-alpha emission and its aeronomical significance

It is pointed out that the intensity of the Lyman-alpha emission is a good indicator of the principal aeronomical processes on the major planets. The high-resolution ultraviolet spectrometer aboard the Orbiting Astronomical Observatory Copernicus was used in 1980 April and May to detect the Jovian Lyman-alpha emission by spectroscopically discriminating it from other Doppler shifted Lyman-alpha emissions such as those of the geocorona, and the interplanetary medium. Taking into consideration the reported emission data, it appears that an unusually large energy input due to the particle precipitation in the auroral region must have been responsible for the large observed Lyman-alpha intensity during the Voyager encounter. At most other times, the observed Jovian Lyman-alpha intensity can be explained, within the range of statistical uncertainty, by a model that takes into consideration the solar EUV flux, the solar Lyman-alpha flux, the high exospheric temperature, and the eddy diffusion coefficient without energy input from the auroral sources.

Atreya, S. K.↗