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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 721 records · Page 40
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

A large-beam sky survey at millimeter and submillimeter wavelengths made from balloon altitudes

A survey has been made of a quarter of the celestial sphere from balloon altitudes with a telescope having a 1.6-deg beamwidth and two spectral bands: 3-10 kaysers and 10-25 kaysers. The limiting sensitivity of the survey was 10,000 Jy. The galactic disk was detected from 358 to 45 deg galactic longitude. The total far-infrared flux from several regions on the galactic plane measured in this survey is 5-10 times larger than that observed by others using smaller beamwidths and small-amplitude spatial chopping, indicating that a substantial part of the emission comes from extended sources. Two other extended sources were also observed, one in the Cygnus region and the other a spur running off the galactic plane at 130 deg galactic longitude toward the north celestial pole. In addition, lower limits for the spectral index of interstellar dust emission are presented.

Owens, D. K.↗
NASA NTRS1979

Semiconductor millimeter and centimeter wave radiometer for the study of the radiation of an underlying surface

A theoretical and experimental investigation of a superheterodyne radiometer system with input frequency converter and intermediate frequency modulation is presented. Conditions are found, at which the temperature sensitivity of the device does not deteriorate. A sensitivity function to external parameters (temperature, heterodyne power) of a radiometer system with intermediate frequency modulation and a Schottky diode frequency converter is presented and calculated. Use of a frequency converter at the second harmonic of the heterodyne permitted simplication of the radiometer design and the use of a semiconductor heterodyne. A 3 cm range intermediate frequency amplifier permitted the use of centimeter wave radiometer signals. Fluctuation sensitivity of radiometers with a 1 sec time constant is 0.3 K at 3.4 mm and 0.06 K at 3 cm.

Bordonskiy, G. S.↗
NASA NTRS1980

Effect of cage design on characteristics of high-speed-jet-lubricated 35-millimeter-bore ball bearing

Parametric tests were conducted with a 35 mm bore angular contact ball bearing with a double outer land guided cage. Provisions were made for jet lubrication and outer-ring cooling of the bearing. Test conditions included a combined thrust and radial load at nominal shaft speeds of 48,000 rpm, and an oil-in temperature of 394 K (250 F). Successful operation of the test bearing was accomplished up to 2.5 million DN. Test results were compared with those obtained with similar bearing having a single outer land guided cage. Higher temperatures were generated with the double outer land guided cage bearing, and bearing power loss and cage slip were greater. Cooling the outer ring resulted in a decrease in overall bearing operating temperature.

Schuller, F. T.↗
NASA NTRS1978

Progress on millimeter wave Josephson junction mixers

Preset, recyclable Nb point contacts are tested as low-noise Josephson mixers at a signal frequency of 115 GHz. The best result achieved is a mixer noise temperature (single sideband) of 120 K with unity conversion efficiency (SSB) for a junction at 6 K. Variation of mixer properties with temperature and other parameters is presented.

Taur, Y.↗
NASA NTRS1980

Permittivity of ice and water at millimeter wavelengths

Measurements of reflectivity of water and ice at 100 GHz, 140 GHz, and 180 GHz are reported. Measurements on water covered the temperature range 0 C to 50 C. No anomalies in the dielectric properties of water due to the presence of either salts or organic matter were found. The reflectivity of water and its temperature dependence are consistent with recent dielectric property models derived from data at other wavelengths. The index of refraction of fresh ice is constant at 1.78 throughout this regions.

Blue, M. D.↗
NASA NTRS1981

Ice/frost detection using millimeter wave radiometry

A series of ice detection tests was performed on the shuttle external tank (ET) and on ET target samples using a 35/95 GHz instrumentation radiometer. Ice was formed using liquid nitrogen and water spray inside a test enclosure containing ET spray on foam insulation samples. During cryogenic fueling operations prior to the shuttle orbiter engine firing tests, ice was formed with freon and water over a one meter square section of the ET LOX tank. Data analysis was performed on the ice signatures, collected by the radiometer, using Georgia Tech computing facilities. Data analysis technique developed include: ice signature images of scanned ET target; pixel temperature contour plots; time correlation of target data with ice present versus no ice formation; and ice signature radiometric temperature statistical data, i.e., mean, variance, and standard deviation.

Gagliano, J. A.↗
NASA NTRS1980

1.0 millimeter maps and radial density distributions of Southern H II/molecular cloud complexes

Measurements of the 1.0-mm continuum emission from seven Southern Hemisphere H II region/molecular cloud complexes located in the inner part of the Galaxy near the galactic plane are presented. The sources were mapped based on observations made by a remote-controlled prime focus infrared photometer on the Cerro Tololo 4-m telescope at a resolution of 65 arcsec. The morphologies and physical characteristics of the sources investigated are found to be similar, with dust column densities of 0.006-0.030 g/sq cm, linear extents of 1.5-3 pc, total masses of 20,000-100,000 solar masses and infrared luminosities between 2 and 4 x 10 to the 6th solar luminosities. In all cases, the dense, extended dust envelopes are observed to be singly peaked and centered about one or more compact near-infrared sources, with a radial density distribution around the central peak proportional to the -1.5 power of the radius as in other extended 1.0-mm continuum sources.

Cheung, L. H.↗
NASA NTRS1981

Near millimeter wave bandpass filters

The properties of bandpass filters for broadband photometry are reported in the 3-12/cm frequency range. The filters are based on a combination of capacitive grids deposited on thick Mylar substrates and are designed to have very high out-of-band rejection. Low frequencies are blocked by a thick grill that consists of a hexagonal grid of circular holes in a thick metal plate.

Timusk, T.↗
NASA NTRS1980

Advanced millimeter wave imaging systems

Unique techniques are being utilized to develop self-contained imaging radiometers operating at single and multiple frequencies near 35, 95 and 183 GHz. These techniques include medium to large antennas for high spatial resolution, lowloss open structures for RF confinemnt and calibration, wide bandwidths for good sensitivity plus total automation of the unit operation and data collection. Applications include: detection of severe storms, imaging of motor vehicles, and the remote sensing of changes in material properties.

Schuchardt, J. M.↗
NASA NTRS1981

Near-millimeter spectrum of the microwave background

A description is given of a method for the measurement of the cosmic microwave background (CMB) spectrum. A helium-cooled, balloon-borne spectrophotometer was used to measure the emission spectrum of the night sky over the frequency range 1.7-40/cm. The apparatus was calibrated using a blackbody source at a variety of temperatures both before and after the flight. It is shown that the spectrum of the CMB peaks at 6/cm and is approximately that of a blackbody out to several times that frequency. The measured flux is also found to be equivalent to that from a blackbody in the temperature range from 2.88 to 3.09 K. The data set resulting from the combination of these measurements with previous observations of the CMB covers three decades in frequency, and is compared with various CMB models.

Woody, D. P.↗
NASA NTRS1982

Research in millimeter wave techniques

Subharmonically pumped mixers were ascended and tested. A computerized version of the automatic noise figure measurement system was developed. Impedance matching techniques suitable for these types of mixers were investigated. Narrow and broadband (one octave) matching networks for the subharmonic mixers were designed. The automatic mixer noise figure test facility was completed. Subharmonic mixers and the systems that use them at 183 and 220 GHz were evaluated and characterized.

Forsythe, R. E.↗
NASA NTRS1982

The JPL millimeter, submillimeter and microwave line catalog

The catalog includes molecules of interest in the interstellar medium, in planetary atmospheres and in the Earth's atmosphere. Different units than those on the AFGL tape are used. For citing line frequencies in the microwave region. Either the experimental errors or the propagation of errors from the fit are included on the tape. This gives an estimate of how accurate the frequencies are. The intensity units are defined as follows: the logarithm of the intensity unit is the cross section times the frequency in MHz. This is essentially the same unit as on the AFGL tape, but contains fewer factors of the speed of light. The catalog is available to the scientific community either as a tape or on microfiche (filmed in frequency sorted and molecule sorted format).

Pickett, H.↗
NASA NTRS1981

Laboratory millimeter and submillimeter spectra of CO/+/

The strong electric dipole-allowed transitions of the molecular ion CO(+) in the region 235-470 GHz have been measured in the laboratory. The laboratory spectra at 235 GHz appear to confirm the claim by Erickson et al. (1981) to have observed CO(+) in OMC-1.

Sastry, K. V. L. N.↗