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Results for “Fabry-Perot interferometers”

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At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Calibration of the Urbana lidar system

A method for calibrating data obtained by the Urban sodium lidar system is presented. First, an expression relating the number of photocounts originating from a specific altitude range to the soodium concentration is developed. This relation is then simplified by normalizing the sodium photocounts with photocounts originating from the Rayleigh region of the atmosphere. To evaluate the calibration expression, the laser linewidth must be known. Therefore, a method for measuring the laser linewidth using a Fabry-Perot interferometer is given. The laser linewidth was found to be 6 + or - 2.5 pm. Problems due to photomultiplier tube overloading are discussed. Finally, calibrated data is presented. The sodium column abundance exhibits something close to a sinusoidal variation throughout the year with the winter months showing an enhancement of a factor of 5 to 7 over the summer months.

Cerny, T.↗
NASA NTRS1981

Optical observations of thermospheric dynamics at Arecibo

A description is given of wind and temperature data obtained with a 15-cm Fabry-Perot interferometer. The observations were made between February and August 1980 and confirm the details of the conceptual model of Herrero and Meriwether (1980). Attention is given to the method used to analyze the neutral wind field, the zonal winds, the meridional wind, the horizontal wind gradient, the vertical wind velocity, the full wind field, and the neutral temperature. The most regular feature of the neutral wind at Arecibo is the zonal component, which has a peak velocity in the eastward direction near sunset, and decreases in velocity as the night progresses. Both the wind and temperature measurements reported provide ample confirmation of the importance of the equatorial midnight pressure bulge in modifying the dynamic behavior of the nighttime thermosphere at Arecibo.

Burnside, R. G.↗
NASA NTRS1981

Nonthermal line profiles from O/1S/ in the thermospheric nightglow

Generalized composite nonthermal line profiles are calculated for the thermospheric nighttime emission from O(1S) metastable atoms based on an extension to the simple relaxation model of Hays and Walker (1966). It is shown that the Dynamics Explorer Fabry-Perot interferometer will enable accurate values to be obtained for the branching ratio of the O(1S) production reaction and for the excitation exchange collision frequency.

Killeen, T. L.↗
NASA NTRS1982

High-resolution optical measurements of atmospheric winds from space. I - Lower atmosphere molecular absorption

A high-resolution spectroscopic technique, analogous to that used in the thermosphere to measure the vector wind fields in the upper troposphere and stratosphere, is described which uses narrow features in the spectrum of light scattered from the earth's lower atmosphere to provide Doppler information on atmospheric scattering and absorption. It is demonstrated that vector winds can be measured from a satellite throughout the lower atmosphere, using a multiple-etalon Fabry-Perot interferometer of modest aperture. It is found that molecular oxygen and water vapor absorption lines in the spectrum of sunlight scattered by the atmosphere are Doppler-shifted by the line of sight wind, so that they may be used to monitor the global wind systems in the upper troposphere and stratosphere.

Hays, P. B.↗
NASA NTRS1982

Thermosphere zonal winds - Vertical motions and temperature as measured from Dynamics Explorer

Dynamics Explorer 2 has made possible, for the first time, global extent in situ measurements of upper thermosphere neutral particle winds. Zonal and vertical wind components, and the kinetic temperature, are being measured by the Wind and Temperature Spectrometer (WATS), while the Fabry-Perot Interferometer provides the meridional component. The present investigation is concerned with the zonal wind component, the vertical motions, and the temperature measured by the WATS. Preliminary studies of the neutral zonal wind components conducted for many orbits confirm a global pattern of upper thermosphere winds which blow over the earth from the mid-afternoon sector. Velocities range from near zero to a few hundred meters per second. Major perturbations to the basic thermally driven wind patterns are observed in both polar regions where the directions are frequently reversed and where the zonal velocities sometimes exceed 1 km/sec.

Spencer, N. W.↗
NASA NTRS1982

Neutral winds in the polar thermosphere as measured from Dynamics Explorer

Possibilities for experimental investigations related to the study of the dynamics of the thermosphere have been markedly improved by the new instrumentation deployed on the Dynamics Explorer Satellite (DE). The Fabry-Perot interferometer (FPI) on DE measures altitude profiles of the meridional component of the neutral wind below the spacecraft by remotely sensing the Doppler shift of the thermospheric O(1D). The Wind and Temperature Spectrometer (WATS) measures the in situ zonal component of the neutral wind by measuring the angle of arrival of the beam of neutral atoms entering the aperture to a mass spectrometer. A description is provided of data handling procedures, and the first results obtained by combining the data sets from the two instruments are presented. Acquisition and determination of neutral wind vectors from the remote (FPI) and in-situ (WATS) measurements requires careful handling of the data to ensure that the two components relate to the same volume of space.

Killeen, T. L.↗
NASA NTRS1982

The helium 10830 A line in early-type stars - An atlas of Fabry-Perot scans

Representative profiles of He I 10830 A in 65 early-type (O6-A1) stars over a wide range of luminosity are presented. The atlas scans were obtained using the Vaughan Fabry-Perot interferometer on the C. E. K. Mees 0.6 m and KPNO 0.9 m telescopes and usually cover a range of plus or minus 15 A at 1 A resolution with sampling distances between 0.5 A and 2 A depending on the photometer integration time required to reach reasonable Poisson counting statistics. The majority of the scans show very shallow, broad features which do not agree with plane-parallel NLTE model atmosphere calculations of the 10830 line by Auer and Mihalas (1972). Difficulties connected with previous theoretical studies of this line are briefly discussed, and suggestions for possible future modifications to the theory are made.

Meisel, D. D.↗
NASA NTRS1982

Neutral winds in the polar thermosphere as measured from Dynamics Explorer

Remote sensing measurements of the meridional thermospheric neutral wind using the Fabry-Perot Interferometer on Dynamics Explorer have been combined with in-situ measurements of the zonal component using the Wind and Temperature Spectrometer on the same spacecraft. The two data sets with appropriate spatial phasing and averaging determine the vector wind along the track of the polar orbiting spacecraft. A study of fifty-eight passes over the Southern (sunlit) pole has enabled the average Universal Time dependence of the wind field to be determined for essentially a single solar local time cut. The results show the presence of a 'back-ground' wind field driven by solar EUV heating upon which is superposed a circulating wind field driven by high latitude momentum and energy sources.

Killeen, T. L.↗
NASA NTRS1971

A pressure scanning Fabry-Perot magnetometer.

Description of an oscillating magnetic analyzer (KDP crystal plus Glan-Thompson prism) coupled to an echelle-interferometer spectrograph, and of single-slit magnetometer which by pressure variations can be made to scan the entire profiles of the circularly and linearly polarized Zeeman components. Freon gas is used as the scanner gas with wavelength displacements of 0.02 A per 0.1 in. Hg pressure change at the NaD lines. The available scan range is 15 A in the visual spectral region.

Fay, T. D.↗
NASA NTRS1977

Infrared Fabry-Perot and heterodyne spectrometers

The status of infrared instrumentation for astronomical investigations at U.C. Berkeley is described with emphasis on the techniques of high spectral and spatial resolution. Present instrumentation includes three Fabry-Perot spectrometers for the 10, 20, and 100 micron wavelength regions, a submillimeter receiver using an optically pumped laser, a 10 micron heterodyne spectrometer for studies of planetary atmospheres, and a 2-element 10 micron stellar interferometer for measuring the angular diameters of infrared stars.

Betz, A.↗