SEARCH · Search NASA
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.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Report discusses calibration and operation of conceptual Focus Mission Interferometer (FMI), consisting of component instruments mounted at widely separated locations on large truss structure in orbit 1,400 km above Earth. Includes six telescopes in linear array. Outputs combined in pairlike fashion so FMI operates as three distinct two-telescope interferometers. Accurate enough for submilliarcsecond astrometry.
Video system combines images from visible spectrum and from three bands in infrared spectrum to produce color-coded display in which hydrogen fires distinguished from other sources of heat. Includes linear array of 64 discrete lead selenide mid-infrared detectors operating at room temperature. Images overlaid on black and white image of same scene from standard commercial video camera. In final image, hydrogen fires appear red; carbon-based fires, blue; and other hot objects, mainly green and combinations of green and red. Where no thermal source present, image remains in black and white. System enables high degree of discrimination between hydrogen flames and other thermal emitters.
Algorithm performs maximum-likelihood construction of image of scene scanned nonuniformly by linear array of photodetectors, responses of which unequal. Developed to postprocess data acquired by scanning telescope aboard Infrared Astronomical Satellite (IRAS), also adaptable to generation of high-resolution imagery from data acquired in other nonuniform-scanning applications. Achievable resolution not limited by finite size of detectors, and increases with density of scans. With sufficiently dense scans, one obtains resolution beyond diffraction limit of imaging optics.
Localized velocity, temperature, and species concentration measurements in rocket flow fields are needed to evaluate predictive computational fluid dynamics (CFD) codes and identify causes of poor rocket performance. Velocity, temperature, and total number density information have been successfully extracted from spectrally resolved Rayleigh scattering in the plume of small hydrogen/oxygen rockets. Light from a narrow band laser is scattered from the moving molecules with a Doppler shifted frequency. Two components of the velocity can be extracted by observing the scattered light from two directions. Thermal broadening of the scattered light provides a measure of the temperature, while the integrated scattering intensity is proportional to the number density. Spontaneous Raman scattering has been used to measure temperature and species concentration in similar plumes. Light from a dye laser is scattered by molecules in the rocket plume. Raman spectra scattered from major species are resolved by observing the inelastically scattered light with linear array mounted to a spectrometer. Temperature and oxygen concentrations have been extracted by fitting a model function to the measured Raman spectrum. Results of measurements on small rockets mounted inside a high altitude chamber using both diagnostic techniques are reported.
Laser altimetry provides an active, high-resolution, high-accuracy method for measurement of planetary and asteroid surface topography. The basis of the measurement is the timing of the roundtrip propagation of short-duration pulses of laser radiation between a spacecraft and the surface. Vertical, or elevation, resolution of the altimetry measurement is determined primarily by laser pulse width, surface-induced spreading in time of the reflected pulse, and the timing precision of the altimeter electronics. With conventional gain-switched pulses from solid-state lasers and nanosecond resolution timing electronics, submeter vertical range resolution is possible anywhere from orbital altitudes of approximately 1 km to altitudes of several hundred kilometers. Horizontal resolution is a function of laser beam footprint size at the surface and the spacing between successive laser pulses. Laser divergence angle and altimeter platform height above the surface determine the laser footprint size at the surface, while laser pulse repetition rate, laser transmitter beam configuration, and altimeter platform velocity determine the spacing between successive laser pulses. Multiple laser transmitters in a single laser altimeter instrument that is orbiting above a planetary or asteroid surface could provide across-track as well as along-track coverage that can be used to construct a range image (i.e., topographic map) of the surface. We are developing a pushbroom laser altimeter instrument concept that utilizes a linear array of laser transmitters to provide contiguous across-track and along-track data. The laser technology is based on the emerging monolithic combination of individual, 1-sq cm diode-pumped Nd:YAG laser pulse emitters. Details of the multi-emitter laser transmitter technology, the instrument configuration, and performance calculations for a realistic Discovery-class mission will be presented.
The design, initial calibration, and performance evaluations of a portable short wave infrared (SWIR) spectroradiometer are described. The spectroradiometer covers the range from 1.1 to 2.5 microns with a spectral resolution that may be varied from less than 10 nm to more than 100 nm. A single spectrum is acquired in about 2 sec. The SNR is about 230 at a wavelength of 2.2 microns for a Lambertian surface of 90-percent reflectance illuminated by the sun at normal incidence with 14.8-nm resolution, a 25 C background temperature, and no atmospheric attenuation. FOV-defining optics are coupled by a flexible fiber-optics bundle to the spectroradiometer, which consists of a concave holographic diffraction grating with a flat focal field imaged onto a 1024-element platinum silicide linear-array detector.
Basic characteristics of several configurations of coplanar microstrip parasitic subarrays consisting of one fed patch and two or more parasitic patches were investigated by means of a spectral-domain full-wave analysis and the moment method analysis. Results are presented for radiating- and nonradiating edge-coupled three-element linear subarrays and for a five-patch cross. A comparison of the theoretical input impedance results obtained by the analysis of a three-element linear array showed a reasonable agreement between computed and measured R and X values.
A multiple fiber-optic particle sizing probe which uses a linear array of 11 optical fibers positioned in the focal plane of a graded index microlens is presented. The probe, a compact optical spectrum analyzer, provides simultaneous filtering of the angular spectrum of an extended quasi-monochromatic source. Active and passive configurations provide accurate measurements of the particle size distributions. The multiple fiber-optic probe together with processing electronics is a particle sizing sensor which yields the size distribution within 1-2 min.
Considerable evidence points to a Martian origin of the SNC meteorites. One of these meteorites, Nakhla, contains a leachable component which has an elevated Xe-129/Xe-132 ratio relative to its Kr-84/Xe-132 ratio when compared to the approximately linear array defined by Chassigny, most shergottites, and lithology C of EETA 79001. This array is thought to be a mixing line between Martian mantle and Martian atmosphere. The leachable component probably consists in part of iddingsite, an alteration product produced by interaction of olivine with aqueous fluid at temperatures lower than 150 C. The radiogenic Xe component may represent a distinct reservoir in the Martian crust or mantle. More plausibly, it is Martian atmosphere, fractionated by solution in liquid water and by interaction with sediment. The crystallization age of Nakhla is 1.3 Ga. Its low shock state suggests that it was ejected from near the surface of Mars. Liquid water is required for the formation of iddingsite. These observations provide further evidence for the near surface existence of aqueous fluids more recently than 1.3 Ga.
In this Progress Report, we describe our current research activities concerning the development and implementation of advanced ultrasonic nondestructive evaluation methods applied to the characterization of stitched composite materials and bonded aluminum plate specimens. One purpose of this investigation is to identify and characterize specific features of polar backscatter interrogation which enhance the ability of ultrasound to detect flaws in a stitched composite laminate. Another focus is to explore the feasibility of implementing medical linear array imaging technology as a viable ultrasonic-based nondestructive evaluation method to inspect and characterize bonded aluminum lap joints. As an approach to implementing quantitative ultrasonic inspection methods to both of these materials, we focus on the physics that underlies the detection of flaws in such materials.
The effects of influence of shock wave propagation on the energy spectrum of accelerated particles that lead to different production rates of radionuclides, in particular, Mn-53, on small scales in the early solar system are shown. Search for evidence for extinct Mn-53 has stimulated investigations of Cr isotope anomalies in meteorites. The linear correlation between the magnitude of the Cr-53* excesses and the Mn/Cr ratio that unambiguously proves the in situ decay of Mn-53 was detected, really, in different mineral phases of some carbonaceous and enstatite chondrites, primitive achondrites, pallasites and iron meteorites. However, the data on the Cr-53* excess rarely defines a single linear array on a Mn-53-Cr-52 evolution diagram even for meteorites of the same chemical group. A clear isochron with Mn-53/Mn-55 = 4.4 plus or minus 1.0 x 10(exp -5) (in range of approximately 2.4 to approximately 9 x 10(exp -5)) is observed for CAI of the Allende C3-chondrite while the data for the Murchison C2- and Orgueil C1-chondrites fall much lower corresponding rather to Mn-53/Mn-55 less than 2 x 10(exp -5). In the case of iron meteorites it ranges from less than 5 x 10(exp -8) to less than 5 x 10(exp -5).
The etalon interferometer, or Fabry-Perot interferometer (FPI), with its high throughput and high spectral resolution was widely used in the remote-sensing measurements of the earth's atmospheric composition, winds, and temperatures. The most recent satellite instruments include the Fabry-Perot interferometer flown on the Dynamics Explorer-2 (DE-2) and the High Resolution Doppler Imager (HRDI) to be flown on the Upper Atmosphere Research Satellite (UARS). These instruments measure the Doppler line profiles of the emission and absorption of certain atmospheric species (such as atomic oxygen) in the visible spectral region. The successful space flight of DE-FPI and the test and delivery of UARS-HRDI demonstrated the extremely high spectral resolution and ruggedness of the etalon system for the remote sensing of earth and planetary atmospheres. Recently, an innovative FPI focal plane detection technique called the Circle-to-Line Interferometer Optical (CLIO) system was invented at the Space Physics Research Laboratory (SPRL). The CLIO simplifies the FPI focal plane detection process by converting the circular rings or fringes into a linear pattern similar to that produced by a conventional spectrometer, while retaining the throughput advantage of the etalon interferometer. CLIO makes the use of linear array detectors more practical and efficient with FPI, the combination of FPI and CLIO represents a very promising new technique for the remote sensing of the lower atmospheres of Earth, Mars, Venus, Neptune, and other planets. The Multiorder Etalon Spectrometer (MOES), as a combination of the rugged etalon and the CLIO, compares very favorably to other spaceborne optical instruments in terms of performance versus complexity. The feasibility of an advanced etalon spectrometer for the remote sensing of tropospheric trace species, particularly carbon monoxide (CO), nitrous oxide (N2O), and methane (CH4) was discussed. The etalon atmospheric spectroscopy techniques are described, instrument design and related technical issues are discussed. The primary objective is to establish the concept of atmospheric spectroscopy with the CLIO and etalon system and its applications for the measurements of tropospheric trace species analyze system requirements and performance, determine the feasibility of components and subsystem implementation with available technology, and develop inversion algorithm for retrieval simulation and data analysis.
The objective of the present work is to study the mixing characteristics of a linear array of supersonic rectangular jets under conditions of screech synchronization. The screech synchronization at a fully expanded jet Mach number of 1.61 is achieved by a precise adjustment of the internozzle spacing. To our knowledge, such an experiment on the resonant mixing of screech synchronized multiple rectangular jets has not been reported before. The results are compared with the case where the screech was suppressed in the multijet configuration.
Electronic circuit provides bar-graph display of difference between carrier frequency of pulsed laser transmitter and frequency of another laser serving as local oscillator in receiver. Display device linear array of light-emitting diodes (LED's), each representing 1-MHz portion of beat-frequency range from 20 to 40 MHz. Middle LED and neighbors green; LED's representing edges of passband yellow; LED's of frequencies outside passband red. Operator determines approximate relative frequency of transmitter at a glance by observing color and position of illuminated LED.
Proposed optoelectronic instrument measures tilt of object about single horizontal axis by measuring change of position and orientation of laser beam reflected from hanging mirror. Mirror remains vertical while rest of instrument rotated with object. Optoelectronic inclinometer measures tilt about gimbal axis by measuring change in position and orientation of beam of light reflected from mirror hanging in gimbal. Maximum amount of tilt about pivot axis of pendulum that instrument tolerates depends on size of mirror and physical size of linear array and spacing of components. Compensating lens included to correct for nonlinearity and to ensure that beam continued to fall on array throughout desired angular range of instrument.
Knowledge of the global scale distribution of atmospheric ozone and its temporal variability can be achieved using a satellite-based nadir-viewing device making high spectral resolution measurements with high signal-to-noise ratios. This would enable observation in the pressure-broadened wings of strong O3 lines while minimizing the impact of undesirable signal contributions associated with, for example, the terrestrial surface and interfering species. The Fabry-Perot interferometer (FPI) provides high spectral resolution and high throughput capabilities that are essential for this measurement task. The periodic nature of the Fabry-Perot instrument function can be advantageous when observation of periodic spectra is desired. However, for most applications, additional optical elements are necessary to reduce the effect of unwanted passbands. This is frequently accomplished using additional Fabry-Perot etalons in a series configuration in conjunction with a bandpass filter. This paper discusses a Fabry-Perot interferometer conceptual instrument design to achieve tropospheric and total ozone monitoring capability from a satellite-based nadir-viewing geometry. The design involves a double-etalon fixed-gap series configuration FPI along with an ultra-narrow bandpass filter to achieve single-order operation with an overall spectral resolution of approximately .068 cm(exp -1). The impact of inter-etalon reflections has been reduced to acceptable levels by placement of a slightly attenuating medium in between the etalons. A passive device is selected for low power consumption, and continuous day/night coverage, independent of solar zenith angle, is enabled by observing within the strong 9.6 micron ozone infrared band. The IR-FPI detection will be performed through implementation of the new Circle to Line Interferometer Optical (CLIO) system, developed by researchers at the Space Physics Research Laboratory (SPRL) of the University of Michigan, to accomplish focal plane fringe detection; the CLIO system converts the circular interferometric fringes into a linear pattern which then can be detected by conventional linear array detectors. A multiplex signal advantage is achievable as all necessary frequencies can be measured simultaneously using a multichannel configuration. Through proper selection of channel spectral regions, the FPI optimized for tropospheric O3 measurements can simultaneously observe a stratospheric component and thus the total O3 column abundance.
Two optical systems capable of measuring model attitude and deformation were compared to inertial devices employed to acquire wind tunnel model angle of attack measurements during the sting mounted full span 30% geometric scale flexible configuration of the Northrop Grumman Unmanned Combat Air Vehicle (UCAV) installed in the NASA Langley Transonic Dynamics Tunnel (TDT). The overall purpose of the test at TDT was to evaluate smart materials and structures adaptive wing technology. The optical techniques that were compared to inertial devices employed to measure angle of attack for this test were: (1) an Optotrak (registered) system, an optical system consisting of two sensors, each containing a pair of orthogonally oriented linear arrays to compute spatial positions of a set of active markers; and (2) Video Model Deformation (VMD) system, providing a single view of passive targets using a constrained photogrammetric solution whose primary function was to measure wing and control surface deformations. The Optotrak system was installed for this test for the first time at TDT in order to assess the usefulness of the system for future static and dynamic deformation measurements.
We studied 14 chondrules separated from LEW85332, an ungrouped type-3 carbonaceous chondrite related to CR chondrites; 23 elements were determined by neutron activation and the chondrules were characterized petrographically. Oxygen isotopic compositions were determined by R. N. Clayton and T. K. Mayeda for seven chondrules. Chondrule abundance ratios tend to form one of two distinct patterns. In low FeO chondrules, refractory lithophile patterns are flat (i.e., unfractionated); siderophile abundances are high and show a small decrease with increasing volatility. Although high FeO chondrules also have flat refractory lithophile abundance patterns, siderophile abundances are highly fractionated; refractory Ir is very low and Fe is very high relative to other siderophiles. We suggest that the low FeO chondrules in LEW85332 formed early in nebular history when metal was intimately mixed with silicates in the chondrule precursors, and that the viscosity of the liquid-solid mix was too high to permit expulsion of the metal by centrifugal action; their porphyritic structures are consistent with incomplete melting, which would result in relatively high viscosities. When the high FeO chondrules formed somewhat later, much of the Fe was oxidized and the melting of precursors was more extensive, FeO and other oxidized siderophiles were retained in the silicate liquid, and metal was lost, possibly expelled from low viscosity chondrule melts. The O isotopic compositions of the chondrules form a linear array of slope 0.93 +/- 0.05 on a three-isotope diagram, parallel to the carbonaceous chondrite anhydrous minerals (CCAM) line and a CR chondrule array, but offset from the latter by -1% in (delta)O-18. Some or all of this offset may reflect incorporation of O from Antarctic water during weathering. Chondrule (Delta)O-17 values correlate positively with FeO, possibly indicating that the (Delta)O-17 of the nebular gas composition increased with time. The chemical and O isotopic data suggest a temporal sequence extending from early, low FeO to late high FeO chondrules.