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Chin, G.

Publications and source records attributed to Chin, G..

47 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Discovery of natural gain amplification in the 10-micrometer carbon dioxide laser bands on Mars - A natural laser

Fully resolved intensity profiles of various lines in the carbon dioxide band at 10.4 micrometers have been measured on Mars with an infrared heterodyne spectrometer. Analysis of the line shapes shows that the Mars atmosphere exhibits positive gain in these lines. The detection of natural optical gain amplification enables identification of these lines as a definite natural laser.

Mumma, M. J.↗
NASA NTRS1981

Bulk and integrated acousto-optic spectrometers for molecular astronomy with heterodyne spectrometers

A survey of acousto-optic spectrometers for molecular astronomy is presented, noting a technique of combining the acoustic bending of a collimated coherent light beam with a Bragg cell followed by an array of sensitive photodetectors. This acousto-optic spectrometer has a large bandwidth, a large number of channels, high resolution, and is energy efficient. Receiver development has concentrated on high-frequency heterodyne systems for the study of the chemical composition of the interstellar medium. RF spectrometers employing acousto-optic diffraction cells are described. Acousto-optic techniques have been suggested for applications to electronic warfare, electronic countermeasures and electronic support systems. Plans to use integrated optics for the further miniaturization of acousto-optic spectrometers are described. Bulk acousto-optic spectrometers with 300 MHz and 1 GHz bandwidths are being developed for use in the back-end of high-frequency heterodyne receivers for astronomical research.

Chin, G.↗
NASA NTRS1981

433 micron laser heterodyne observations of galactic CO from Mauna Kea

A submillimeter heterodyne radiometer, developed for astronomical applications, uses an optically pumped laser local oscillator and a quasi-optical Schottky diode mixer. The resultant telescope-mounted system, which has a noise temperature less than 4000 K (double sideband) and high frequency and spatial resolution, has been used to detect the J = 6 to 5 rotational transition of carbon monoxide at 434 micrometers in the Orion molecular clouds. The measurements, when compared with previous millimeter-wave data, indicate that the broad carbon monoxide emission feature is produced by an optically thin gas whose temperature exceeds 180 K.

Buhl, D.↗
NASA NTRS1980

Discovery of natural gain amplification in the 10 muon m CO2 laser bands on Mars: The first definite natural laser

Fully resolved intensity profiles of various lines in the CO2 bands at 9.4 micrometers and 10.4 micrometers were measured on Mars using an infrared heterodyne spectrometer. Analysis of the line shapes shows that the Mars atmosphere exhibits positive gain on these lines, providing the first definite detection of natural optical gain amplification and enabling identification of these lines as the first definite natural laser ever discovered.

Mumma, M.↗
NASA NTRS1980

Acousto-optic spectrometer for radio astronomy

A prototype acousto-optic spectrometer which uses a discrete bulk acoustic wave Itek Bragg cell, 5 mW Helium Neon laser, and a 1024 element Reticon charge coupled photodiode array is described. The analog signals from the photodiode array are digitized, added, and stored in a very high speed custom built multiplexer board which allows synchronous detection of weak signals to be performed. The experiment is controlled and the data are displayed and stored with an LSI-2 microcomputer system with dual floppy discs. The performance of the prototype acousto-optic spectrometer obtained from initial tests is reported.

Chin, G.↗
NASA NTRS1980

Vibrationally excited silicon monoxide masers

Published data on a select group of SiO maser sources have been analyzed for velocity variations as a function of phase. No apparent correlation was found to a level of about 2 km/s. This places constraints on the location of the maser molecules. Such a correlation should be present at some level. The implications for future high resolution infrared measurements are discussed.

Buhl, D.↗
NASA NTRS1980

A 10 micron heterodyne receiver for ultra high resolution astronomical spectroscopy

An improved CO2 laser heterodyne spectrometer is examined. The present system uses reflective optics to eliminate refocusing at different wavelengths, and the local oscillator is a line-center-stabilized isotopic CO2 laser. A tunable diffraction grating makes possible easy and rapid selection of over 50 transitions per isotope of CO2. The IF (0 to 1.6 GHz) from the HgCdTe photomizer is analyzed by a 128-channel filter bank, consisting of 64 tunable 5-MHz filters and 64 fixed 25-MHz RF filters. These filters provide resolving powers of about 1,000,000 to 10,000,000 and velocity resolution of 50 to 250 m/sec; their output is synchronously detected, integrated, multiplexed and stored in a buffer memory for the desired integration period. Kitt Peak observations show the wide spectral coverage, wide mixer and electronics bandwidth, and high sensitivity of the system.

Buhl, D.↗
NASA NTRS1980

Acousto-optic spectrometer for radio astronomy

Recent developments in acousto-optic techniques and in photodetector arrays have made feasible a new type of RF spectrometer, offering the advantages of wide bandwidth, high resolution, large number of channels in compact, lightweight, energy efficient, and relatively low cost systems. Such a system employs an acousto-optic diffraction cell which serves the key role of converting RF signals to ultrasonic traveling-waves modulating the optical index of the cell. The cell is illuminated across its aperture by a monochromatic laser beam. A fraction of the light is diffracted by the acoustic waves. A focusing lens follows the cell and essentially performs a Fourier transform of the RF signal into a far-field intensity pattern. CSIRO in Australia and the Tokyo Astronomical Observatory in Japan have taken the lead in using acousto-optic techniques in astronomical applications. The first practical device was successfully made at CSIRO for obtaining dynamical spectrographs of solar radio emission.

Chin, G.↗
NASA NTRS1979

Search for H2 emission at 2.1 microns in ten southern hemisphere sources

The 2.12-micron line of molecular hydrogen was searched for in emission from a variety of southern hemisphere objects, including infrared sources associated with molecular clouds and H II regions, the galactic center, and three external galaxies. Negative results are reported for all sources.

Scoville, N. Z.↗
NASA NTRS1977

The molecular complexes in Orion

Line emission from CO at 2.6 mm is observed over an area of 28 square degrees in the Orion region. Most of the emission comes from two giant molecular complexes, roughly associated with Ori B and Ori A. The latter provides the best example of a giant molecular complex at the end of a sequence of OB association subgroups of decreasing age. This complex is apparently rotating with an angular velocity 4.5 by 10 to the -15th power per sec, but in a direction opposed to the Galactic rotation. The apparently denser parts of the cloud are rotating at a somewhat greater angular velocity. The total mass of the molecular gas derived from the observations is 200,000 solar masses, implying that roughly half the matter in this region is in the form of molecular hydrogen.

Kutner, M. L.↗