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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Measurements of pressure-induced shifts in the 1-0 and 2-0 bands of HF and in the 2-0 bands of HCl-35 and HCl-37

Fourier absorption spectra of HCl and HF measured at room temperature and low pressures were found to indicate pressure-induced shifts of the spectral lines at gas pressures of only 10 torr. Self-induced shifts were determined for the HF 2-0 band and for the HCl-35 and HCl-37 2-0 bands, and shift oscillations in the 2-0 bands due to near-resonant dipole-dipole interactions between the two gases were also evaluated. Separate measurements of pressure-induced shifts in the HF 1-0 and 2-0 bands and in both isotopic HCl bands were obtained using argon, neon, nitrogen, and CO2 separately as the perturbing gases.

Guelachvili, G.↗
NASA NTRS1984

Venus banded terrain: Evaluation of tectonic models for the origin of banding

A tectonic orgin for Venus banded terrain is consistent with band spacing. Both compressional (folding) and extensional models for band formation can fit present observations. Band spacing cannot distinguish among scenarios for global heat loss and for the origin of highland terrain. Tectonic models for band formation indicate that the surface brittle layer in the venus highlands is no more than a few kilometers thick.

Solomon, S. C.↗
NASA NTRS1985

Comparison of band model calculations of upper atmospheric cooling rates for the 15-micrometer carbon dioxide band

Within the atmosphere of the earth, absorption and emission of thermal radiation by the 15-micron CO2 bands are the largest contributors to infrared cooling rates in the stratosphere. Various techniques for calculating cooling rates due to these bands have been described. These techniques can be classified into one of two categories, including 'exact' or line-by-line calculations and other methods. The latter methods are based on broad band emissivity and band absorptance formulations. The present paper has the objective to present comparisons of the considered computational approaches. It was found that the best agreement with the exact line-by-line calculations of Fels and Schwarzkopf (1981) could be obtained by making use of a new Doppler band model which is described in the appendix of the paper.

Boughner, R. E.↗
NASA NTRS2000

Passive Microwave Measurements Over Conifer Forests at L-Band and C-Band

Measurements have been made at L-band and C-band over conifer forests in Virginia to study the response of passive microwave instruments to biomass and soil moisture. A series of aircraft measurements were made in July, August and November, 1999 over relatively homogenous conifer forests of varying biomass. Three radiometers participated in these measurements. These were: 1) the L-band radiometer ESTAR, a horizontally polarized synthetic aperture radiometer which has been used extensively in past measurements of soil moisture; 2) the L-band radiometer SLFMR, a vertically polarized cross-track scanner which has been used successfully in the past for mapping sea surface salinity; and 3) The ACMR, a new C-band radiometer which operates at V- and H-polarization and in the configuration for these experiments did not scan. All three radiometers were flown on the NASA P-3 aircraft based at the Goddard Space Flight Center's Wallops Flight Facility. The ESTAR and SLFMR were mounted in the bomb bay of the P-3 and imaged across track whereas the ACMR was mounted to look aft at 54 degrees up from nadir. Data was collected at altitudes of 915 meters and 457 meters. The forests consisted of relatively homogeneous "managed" stands of conifer located near Waverly, Virginia. This is a relatively flat area about 30 miles southeast of Richmond, VA with numerous stands of trees being grown for the forestry industry. The stands selected for study consisted of areas of regrowth and mature stands of pine. In addition, a small stand of very large trees was observed. Soil moisture sampling was done in each stand during the aircraft over flights. Data was collected on July 7, August 27, November 15 and November 30, 1999. Measurements were made with ESTAR on all days. The ACMR flew on the summer missions and the SLFMR was present only on the August 27 flight. Soil moisture varied from quite dry on July 7 to quite moist on November 30 (which was shortly after a period of rain). The microwave images clearly distinguish between the different forest stands. Research is continuing to seek a quantitative correlation with biomass and surface soil moisture.

LeVine, D. M.↗
NASA NTRS2015

A Novel Ku-Band/Ka-Band and Ka-Band/E-Band Multimode Waveguide Couplers for Power Measurement of Traveling-Wave Tube Amplifier Harmonic Frequencies

This paper presents the design, fabrication and test results for a novel waveguide multimode directional coupler (MDC). The coupler, fabricated from two dissimilar frequency band waveguides, is capable of isolating power at the second harmonic frequency from the fundamental power at the output port of a traveling-wave tube (TWT) amplifier. Test results from proof-of-concept demonstrations are presented for a Ku-band/Ka-band MDC and a Ka-band/E-band MDC. In addition to power measurements at harmonic frequencies, a potential application of the MDC is in the design of a satellite borne beacon source for atmospheric propagation studies at millimeter-wave (mm-wave) frequencies (Ka-band and E-band).

Wintucky, Edwin G.↗
NASA NTRS2015

Inflatable Antenna for CubeSat: Extension of the Previously Developed S-Band Design to the X-Band

The inflatable antenna for CubeSat is a 1 meter antenna reflector designed with one side reflective Mylar, another side clear Mylar with a patch antenna at the focus. The development of this technology responds to the increasing need for more capable communication systems to allow CubeSats to operate autonomously in interplanetary missions. An initial version of the antenna for the S-Band was developed and tested in both anechoic chamber and vacuum chamber. Recent developments in transceivers and amplifiers for CubeSat at X-band motivated the extension from the S-Band to the X-Band. This paper describes the process of extending the design of the antenna to the X-Band focusing on patch antenna redesign, new manufacturing challenges and initial results of experimental tests.

Babuscia, Alessandra↗
NASA NTRS2018

NISAR L-Band and S-Band Instrument Antennas: Compatibility Test and Results

Abstract—NASA ISRO SAR (NISAR) is one of the next major Earth science flight projects that NASA is currently developing in collaboration with ISRO, the Indian Space Research Organization. Featuring a 12m deployable off-set reflector, similar to SMAP but twice as large, and a dual band, dual polarization feed array, NISAR will measure with great accuracy even the smallest changes on our planet’s landmass, ice-sheet and forests over a 3 year period with a 12-day repeat cycle everywhere on the globe. Two radar systems will be sharing the same reflector, one operating in L-Band and one in S-Band. While the L-Band radar and feed antenna are being developed at Jet Propulsion Laboratory (JPL) for NASA, the S-Band feed antenna is under development at the Space Application Centre (SAC) in Ahmedabad, India, for ISRO. This paper describes the tests that were carried out both at JPL and SAC in order to verify that the level of compatibility between the two feed antennas were within the allocated requirements. Both S-parameters and radiation patterns were measured and compared with calculated predictions.

Harrell, Jefferson A.↗
NASA NTRS2004

Techniques to minimize adjacent band emissions from Earth Exploration Satellites to protect the Space Research (Category B) Earth Stations in the 8400-8450 MHz band

The Earth Exploration Satellites operating in the 8025-8400 MHz band can have strong adjacent band emissions on the8400-8450 MHz band which is allocated for Space Research (Category-B). The unwanted emission may exceed the protection criterion establish by the ITU-R for the protection of the Space Research (Category B) earth stations, i.e., deep-space earth stations. An SFCG Action Item (SF 23/14) was created during the 23rd SFCG meeting to explore technical and operational techniques to reduce the adjacent band emissions. In response to this action item, a study was conducted and results are presented in this document.

adjancent band emission↗
NASA NTRS1971

G-r noise for Auger band-to-band processes.

Expressions for band-to-band Auger recombination, including the effects of photoinduced carriers in intrinsic photoconductors, are presented. They show good agreement with the expressions published by van Vliet (1958) and Long (1967) for g-r noise in intrinsic photoconductors for the case of band-to-band radiative recombination.

Breitzer, D.↗
NASA NTRS1976

Space shuttle engineering and operations support. Isolation between the S-band quad antenna and the S-band payload antenna. Engineering systems analysis

The isolation between the upper S-band quad antenna and the S-band payload antenna on the shuttle orbiter is calculated using a combination of plane surface and curved surface theories along with worst case values. A minimum value of 60 db isolation is predicted based on recent antenna pattern data, antenna locations on the orbiter, curvature effects, dielectric covering effects and edge effects of the payload bay. The calculated value of 60 db is significantly greater than the baseline value of 40 db. Use of the new value will result in the design of smaller, lighter weight and less expensive filters for S-band transponder and the S-band payload interrogator.

Lindsey, J. F.↗
NASA NTRS1982

Stellar luminosity functions in the R, I, J, and K bands obtained by transformation from the visual band

The stellar luminosity function that has been measured in the visual band into the R, I, J, and K bands, where it has not yet been obtained directly, is transformed. The transformation is effected by subdividing the total visual function, which includes all stars, into subluminosity functions for each luminosity class (supergiants through white dwarfs), applying the known (V - D) color, D = R, I, J, K for each spectral type, and then summing the resultant transformed subluminosity functions into a total luminosity function for the band D. Simple analytic forms that accurately fit the transformed luminosity functions are given. Consideration is also given to the possibility of a systematic error resulting from the existence of a very red stellar population not accounted for in the visual band luminosity function

Mamon, G. A.↗
NASA NTRS1984

Investigation of LANDSAT D Thematic Mapper geometric performance: Line to line and band to band registration

The geometric accuray of LANDSAT TM raw data of Toulouse (France) raw data of Mississippi, and preprocessed data of Mississippi was examined using a CDC computer. Analog images were restituted on the VIZIR SEP device. The methods used for line to line and band to band registration are based on automatic correlation techniques and are widely used in automated image to image registration at CNES. Causes of intraband and interband misregistration are identified and statistics are given for both line to line and band to band misregistration.

Begni, G.↗
NASA NTRS1985

Investigation of TM Band-to-band Registration Using the JSC Registration Processor

When the Thematic Mapper (TM) imagery was first received and displayed in the fall of 1982, its radiometric lucidity and geometric fidelity was judged far superior to the multispectral scanner (MSS) imagery. The MSS data from the LANDSAT series of satellites have served well as the mainstay of satellite imagery for the remote sensing community up to now. Therefore, there is great anticipation as to the utility of this new IM imagery to advance the field of remote sensing. The thematic mapper (TM) band to band registration accuracy evaluation was discussed. In particular, the band to band registration accuracies of the TM data in the subpixel region were evaluated using the Johnson Space Center (JSC) registration processor which is ideally suited for this task. The JSC registration processor was also used to register one acquisition to another acquisition of multitemporal TM data acquired over the same ground track. The approach and the rationale behind the task, the description of the data set, the evaluation results, and the preliminary conclusions are discussed.

Yao, S. S.↗
NASA NTRS1988

High resolution absorption cross-sections and band oscillator strengths of the Schumann-Runge absorption bands of isotopic oxygen, (O-18)2, at 79 K

Cross-sections of (O-18)2 at 79 K have been obtained from photoabsorption measurements at various pressures throughout the wavelength region 177.8-197.8 nm with a 6.65 m photoelectric scanning spectrometer equipped with a 2400 lines/mm grating and having an instrumental width (FWHM) of 0.0013 nm. The measured absorption cross-sections of the Schumann-Runge bands (14,0) through (2,0) are, with the exception of the (12,0) band, independent of the instrumental width. The measured cross-sections are presented graphically here and are available at wavenumber intervals of about 0.1/cm as numerical compilations stored on magnetic tape. Band oscillator strengths of those bands have been determined by direct numerical integration of the measured absolute cross-sections and are in excellent agreement with these theoretically calculated values.

Yoshino, K.↗
NASA NTRS2000

Absolute band intensities in the nu19/nu23 (530 cm(-1)) and nu7 (777 cm(-1)) bands of acetone ((CH3)2CO) from 232 to 295 K

Absolute band intensities of acetone ((CH3)2CO) in the nu19/nu23 and nu7 band systems near 530 and 777 cm(-1), respectively, were measured at temperatures of 232, 262 and 295 K, using a Fourier transform infrared (FTIR) spectrometer. No evident temperature dependence for the band intensities was observed. The dipole moments and the fundamental band intensities were derived in the harmonic oscillator approximation. The results are useful for the spectroscopic retrieval of acetone concentrations in the upper atmosphere.

Acetone/chemistry↗
NASA NTRS2009

Generating Ka-Band Signals Using an X-Band Vector Modulator

A breadboard version of a transmitter for radio communication at a carrier frequency of 32 GHz (which is in the Ka band) utilizes a vector modulator operating at a carrier frequency of 8 GHz (the low end of the X band) to generate any of a number of advanced modulations that could include amplitude and/or phase modulation components. The 8-GHz modulated signal is mixed with a 24-GHz signal generated by an upconverter to obtain the desired 32-GHz modulated output. The transmitter is being developed as a prototype of downlink transmitters for transmission of data from spacecraft to Earth at high rates (>100 Mb/s). The transmitter design could also be adapted to terrestrial and Earth/satellite communication links. The advanced modulations (which can include M-ary phase-shift keying (M-PSK), offset phase-shift keying (OPSK), and M-ary quadrature amplitude modulation (M-QAM). These modulations are needed because for a given amount of signal bandwidth, they enable transmission of data at rates greater than those of older, simpler modulation schemes. The transmitter architecture (see figure) was chosen not only to enable generation of the required modulations at 32 GHz but also to reduce the number of components needed to implement the transmitter. Instead of incorporating an 8-GHz signal source, the transmitter utilizes an 8-GHz signal generated by a voltage-controlled oscillator that is part of an X-band transponder with which the fully developed version of this transmitter would be used in the original intended spacecraft application. The oscillator power is divided onto two paths, one of which goes through the vector modulator, the other through amplifiers and a 3 frequency multiplier. Band-pass filters are included downstream of the frequency multiplier to suppress unwanted harmonics.

Smith, Scott↗
NASA NTRS2014

Multi-Band (K- Q- and E-Band) Multi-Tone Millimeter-Wave Frequency Synthesizer for Radio Wave Propagation Studies

This paper presents the design and test results of a multi-band multi-tone millimeter-wave frequency synthesizer, based on a solid-state frequency comb generator. The intended application of the synthesizer is in a space-borne transmitter for radio wave atmospheric studies at K-band (18 to 26.5 GHz), Q-band (37 to 42 GHz), and E-band (71 to 76 GHz). These studies would enable the design of robust multi-Gbps data rate space-to-ground satellite communication links. Lastly, the architecture for a compact multi-tone beacon transmitter, which includes a high frequency synthesizer, a polarizer, and a conical horn antenna, has been investigated for a notional CubeSat based space-to-ground radio wave propagation experiment.

Satellite Communications↗
NASA NTRS1996

MISR Band-to-Band Registration

During the standard geo-rectification processing of the MISR imagery, all four spectral bands belonging to each of the nine MISR cameras are required to be geolocated and co-registered automatically with about one pixel accuracy. Two steps of processing are designed to accomplish this goal: 1)a complex multi-camera geolocation and co-registration of the red spectral band data for all nine cameras, and 2) the co-registration of the other three spectral bands of MISR imagery of each camera using their relationship with the already geolocated red band imagery. This paper addresses the second processing.

geolocationco-registration↗