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At least 667 records · Page 37
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Observations of 1-millimeter continuum radiation from the DR 21 region

Continuum emission at 1 mm has been mapped with 1-min resolution over a 3-min by 8-min area including the compact H II region DR 21, the maser source W75(S)-OH, and the central portions of the surrounding molecular cloud. Peaks in the 1-mm intensity are observed at the positions of DR 21 and W75(S)-OH, and are roughly coincident with less marked peaks in the intensity of HCN and CO emission. An extended component of 1-mm emission is present as well. The principal source of 1-mm radiation is thought to be thermal emission from dust within the molecular gas. The characteristics of this radiation which make it a promising tool for the study of molecular clouds are briefly discussed.

Werner, M. W.↗
NASA NTRS1975

A 100-kHz frequency divider, distribution amplifier

A frequency divider, distribution amplifier module having low phase noise and low phase drift with temperature and high isolation between outputs was developed for use in the hydrogen maser frequency standard, where it divides 1 MHz from the previous frequency divider down to 100 kHz and provides four transistor-transistor logic (TTL) outputs.

Lutes, G.↗
NASA NTRS1976

DSN research and technology support

Continuing testing and refinement of the remote controlled, unattended automated pulsar observing station is noted, along with routine pulsar observations of 22 pulsars. Radar observations of geostationary satellite are discussed. Current status of the 400-kW X-band radar is reported along with routine automatic testing of the stability-reliability of the DSS 13 maser-receiver noise adding radiometer combination. A failure in the Faraday rotation receiving system is noted along with discussion in some detail of the activities of the high power transmitter maintenance facility. Continuation of receiver phase stability testing, specifically the effects of temperature on coaxial cables, is discussed and results reported. A demonstration at full power of the microwave power transmission facility is noted and routine support of the planetary radio astronomy experiment is discussed. Transmission of master clock synchronization signals to overseas DSN stations is also reported.

Jackson, E. B.↗
NASA NTRS1976

DSN research and technology support

The activities of the Venus Station (DSS 13) and the Microwave Test Facility (MTF) during the period April 19 through June 13, 1976, are discussed and progress noted. Continuing reliability testing and computer program refinement of the remote controlled, unattended automated pulsar observing station is noted, along with routine observations of 17 pulsars. Radar observations of a geostationary satellite are reported, along with the routine automatic testing of the stability of the DSS 13 maser-receiving system. Additional testing of thermal characteristics of semiflexible coaxial cables is reported, along with phase stabilization measurements thereon. Routine support of the planetary radio astronomy experiment, with 43.25 hours of observations of Jupiter and various radio calibration sources, is reported, along with 18.75 hours of differential VLBI observations in conjunction with Australia, DSS 43. Modifications of the clock synchronization winterization system are reported, along with a discussion of the activities of the DSN High-Power Transmitter Maintenance Facility.

Jackson, E. B.↗
NASA NTRS1975

Confirmation of interstellar N2H/+/

The proposed identification of the triplet of interstellar lines recently discovered at 93.174 GHz with the molecular ion N2H(+) is confirmed by resolving the predicted hyperfine structure of the inner nitrogen nucleus in the narrow-line molecular source OMC-2 in the Orion Nebula. The hyperfine constants of N2H(+) are derived from the observational data, and the rest center frequency of the J = 1-0 rotational transition is determined. It is noted that the full width at half-maximum of the weakest line (F sub 1 = 0-1) is only 230 kHz (0.74 km/sec in radial velocity), making it the narrowest molecular emission line (excluding maser point sources) thus far observed in the direction of a H II region or IR source.

Thaddeus, P.↗
NASA NTRS1976

Radio continuum measurements of compact H II regions and other sources

Results are reported for measurements of the flux densities of 33 sources at wavelengths of 13, 4, and 2 cm, which were conducted using the NASA/JPL Deep Space Network 64-m antenna at Goldstone, Calif. Besides compact H II regions, the sources included five Uhuru X-ray sources, several IR sources, an extragalactic radio source, and a H2O maser. The Lyman continuum flux is derived from the measured radio flux and the assumed distance and temperature for 10 possible H II regions; the spectra of previously known sources are extended to higher frequencies, and upper limits are placed on the flux densities for the five X-ray sources. New compact H II regions are found in the bright nebula M78, the nebula K5, and the Ophiuchus dark cloud/IR region.

Matsakis, D. N.↗
NASA NTRS1976

Interstellar molecules

Progress in the discovery and study of interstellar molecules is summarized. The 36 molecular species thus far identified in interstellar space are listed in several groups which include simple hydrides, oxides, and sulfides, various derivatives of ammonia, molecules involving linear carbon chains, cyanides, and molecules related in structure to formaldehyde, alcohols, or ethers. Several free radicals are described, the discovery of molecules in external galaxies is discussed, and possible mechanisms for molecular formation are noted. Methods for examining relative isotopic abundances by measuring molecules in interstellar clouds are outlined, mechanisms for the excitation of interstellar molecules are reviewed, and values are presented for the C-12/C-13 abundance ratio in a number of interstellar clouds. The detection of interstellar masers is discussed along with pumping mechanisms and masing transitions in H2CO, CH, OH, and SiO. The nature of dense interstellar clouds is examined in terms of several simple and complex cloud models, with emphasis on multiple condensation models.

Townes, C. H.↗
NASA NTRS1976

Infrared spectrophotometry of OH 231.8 + 4.2 identified with OH 0739-14

Infrared spectrophotometry from 2.1 to 4.1 microns and from 7.7 to 13.3 microns of the peculiar OH maser source OH 231.8 + 4.2 identified with OH 0739-14 is reported. Deep absorption features are found at 3.1 microns and from 8 to 13 microns, and are identified with absorption by cold ices and silicates in the line of sight to the infrared source. The infrared flux is also found to vary. These infrared observations present new difficulties in understanding the nature of the object. Several possibly useful observations of OH 231.8 + 4.2 are suggested.

Gillett, F. C.↗
NASA NTRS1977

Ultrastable-frequency distribution system

System automatically compensates for path perturbations between transmitter (master) and receiver (slave) sites, and thereby allows single source, such as a hydrogen maser, to serve as frequency reference for multiple users. Highly accurate reference can be transmitted at cost much lower than for sophisticated onsite frequency standard.

Macconnell, J. W.↗
NASA NTRS1978

Measuring cryogenic-refrigerator cooling capacity

Temperature-sensing bridge determines liquid reserve level in low-temperature heat exchanger. Device should be of interest to manufacturers of cryogenic refrigerators as well as to those who use them in conjunction with operation of electronic equipment like masers or Josephson junctions.

Wiebe, E. R.↗
NASA NTRS1977

Preliminary demonstration of precision DSN clock synchronization by radio interferometry

A wideband digital data acquisition system has been developed to measure the clock offsets to the 10-ns accuracy required to facilitate three-way spacecraft ranging, to monitor the hydrogen maser frequency standard rates to 1 part in 10 to the forteenth power and to potentially reduce operational costs by replacing the current DSN operational time sync system.

Hurd, W. J.↗
NASA NTRS1977

Dual-frequency feed system for 26-meter antenna conversion

New cassegrain feed cone assemblies were designed as part of the upgrade of three 26-meter diameter antennas to 34-meter diameter with improved performance. The new dual-frequency feed cone (SXD) will provide both S- and X-band feed systems and traveling wave masers, with a reflex reflector system to permit simultaneous operation analogous to the 64-meter antennas. Tasks involved in adding the X-band receiving capability and improving the S-band feed performance in support of Voyager and later missions described in.

Hartop, R. W.↗
NASA NTRS1977

DSN research and technology support

The ongoing activities at the Venus Station (DSS 13) and the Microwave Test Facility (MTF) discussed include: (1) equipment implementation for unattended operation at DSS 13; (2) salvaging of a 20-kW klystron, at a cost savings of several thousand dollars by the DSN High Power Transmitter Facility; (3) extensive tracking activities with the 26-m antenna including DSN Platform Parameters, Multistation Planetary Radar, Helios II Spectrum Broadening Analysis, VLBI Validation, Planetary Radio Astronomy, and Pulsar Rotation Constancy, for a total time of 219-1/4 observing hours; (4) clock synchronization transmissions from the DSS 13 master clock to the overseas 64-m antenna complexes and special implementation activities in support of PV-78; and (5) implementation of a hydrogen maser frequency standard and the pathfinder installation of a utility control system (UCS) and significant station modification and maintenance.

Jackson, E. B.↗
NASA NTRS1976

NASA atomic hydrogen standards program - An update

Some of the design features of NASA hydrogen masers are discussed including the large hydrogen source bulb, the palladium purified, the state selector, the replaceable pumps, the small entrance stem, magnetic shields, the elongated storage bulb, the aluminum cavity, the electronics package, and the autotuner. Attention is also given to the reliability and operating life of these hydrogen atomic standards.

Reinhardt, V. S.↗
NASA NTRS1976

Characteristics of IR variable stars as observed from orbit

A selection of infrared variable stars was studied at wavelength 2.7 microns during 1971-1975 with data from U.S. Air Force satellites. Stars observed in this program are classified as long-period variable stars, semiregular variables, and irregular variables and are among the strongest stellar sources at this wavelength. In addition, a few new, as yet unclassified variable stars were identified during the course of the investigation. Time scales of reproducible variations range from a few weeks to a few years, and amplitudes of variation are as large as a factor of three for stars with periods of order one year. The minimum infrared flux density of a long-period star repeats accurately from one cycle to the next, whereas the maximum flux density was found to be unstable. The correlation of 2.7 micron and radio emission line data from one, well-studied long-period variable is consistent with the hypothesis that the H2O and OH circumstellar masers are saturated, if pumped by the stellar infrared flux near 2.7 microns.

Maran, S. P.↗
NASA NTRS1977

Further observations of new sources in the AFCRL survey

Salient aspects of follow-up observations carried out on new sources discovered earlier in the AFCRL rocket IR sky survey are summarized. Ground-based searches, studies of class properties of the new AFCRL sources (galactic distribution, IR spectra, time variation), and closer examination of some 'unusual objects' are discussed. Brief descriptions are offered of some unusual objects: possible protostars, and specifically CRL 877; H2O masers in the Mon R2 cloud; the Egg Nebula (CRL 2688); CRL 618, with featureless IR spectrum and optical spectrum reminiscent of a planetary nebula; CRL 437 and other objects associated with multiple-reflection nebulae.

Kleinmann, S. G.↗
NASA NTRS1977

SETI - A preliminary search for narrowband signals at microwave frequencies

In the search for intelligent signals of extraterrestrial origin, certain forms of signals merit immediate and special attention. Extremely narrowband signals of spectral width similar to our own television transmissions are most favored energetically and least likely to be confused with natural celestial emission. A search of selected stars has been initiated using observational and data processing techniques optimized for the detection of such signals. These techniques allow simultaneous observation of 10 to the 5th to 10 to the 6th channels within the observed spectral range. About two hundred nearby (within 80 LY) solar type stars have been observed at frequencies near the main microwave transitions of the hydroxyl radical. In addition, several molecular (hydroxyl) masers and other non-thermal sources have been observed in this way in order to uncover any possible fine spectral structure of natural origin and to investigate the potential of such an instrument for radioastronomy.

Cuzzi, J. N.↗
NASA NTRS1979

Ruby c-axis alignment system

System locates C-axis of ruby slab fabricated for maser application to within + or - 3 minutes of arc at room temperature easier and faster than conventional procedures.

Clauss, R. C.↗