SEARCH · Search NASA

Results for “optical center determination”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 181 records · Page 10

All sources NASA NTRS DOE OSTI

NASA NTRSDate not supplied

Cryogenic Fluid In-Situ Liquefaction for Landers: Prototype Demonstration

As the advancement of In-Situ Resource Utilization concepts and systems continue to develop, applicable technology development and maturation continues in parallel. While there are many different ways to use the resources found on other bodies, one of the most prevalent suggested applications is the manufacturing of propellants. One of the key technologies for the eventual use of these propellant production based ISRU systems is the liquefaction and storage of the produced propellants. The most mentioned propellant combinations include oxygen-hydrogen and oxygen-methane. The liquefaction of oxygen in these systems will be different than oxygen liquefaction systems on Earth, which mainly revolves around the distillation of air. These systems have been developed conceptually and many of the components have been previously tested or are in development. However, the need to demonstrate the system level operations still exists. The demonstration of a prototypical oxygen liquefaction system using tube-on-tank broad area cooling was completed to better understanding system level operations during liquefaction activities. Demonstration testing included system performance determination, constant liquefaction demonstrations, and transient liquefaction demonstrations. The demonstrations showed the operational capabilities of the tube-on-tank system with an integrated cryocooler. Additional testing explored subsurface vs ullage introduction of the gaseous oxygen flow stream as well as demonstrating a novel fiber optic sensor that measured the temperature gradients along the fluid center line within the tank.

ISRU↗

NASA NTRS2003

Vertically Resolved Aerosol Optical Properties over the ARM SGP Site

In order to meet one of its goals - to relate observations of radiative fluxes and radiances to the atmospheric composition - the Department of Energy's Atmospheric Radiation Measurement (ARM) program has pursued measurements and modeling activities that attempt to determine how aerosols impact atmospheric radiative transfer, both directly and indirectly. However, significant discrepancies between aerosol properties measured in situ or remotely remain. To this end, the ARM program will conduct an Aerosol Intensive Operational Period (IOP) in May 2003 at the ARM Southern Great Plains (SGP) site in north central Oklahoma. The IOP involves airborne measurements from two airplanes over the heavily instrumented SGP site. We will give an overview of early airborne results obtained aboard Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) Twin Otter aircraft. The aircraft will carry instrumentation to perform in-situ measurements of aerosol absorption, scattering, extinction and particle size including such novel techniques as the photoacoustic and cavity ring-down methods. Aerosol optical depth and extinction will be measured with the NASA Ames Airborne Tracking 14-channel sunphotometer. Furthermore up- and downwelling solar (broadband and spectral) and infrared radiation will be measured using three different instruments. The up-looking radiation instruments will be mounted on a newly developed stabilized platform, which will keep the instruments level up to aircraft pitch and roll angles of 10 degrees. Additional effort will be directed toward measurement of cloud condensation nucleus concentration as a function of supersaturation and relating CCN concentration to aerosol composition and size distribution. This relation is central to description of the aerosol indirect effect.

Schmid, B.↗

NASA NTRS1999

Dual-Laser Probe for Measuring Blade-Tip Clearance Tested

A dual-probe, integrated fiber-optic laser system for measuring blade tip clearance in rotating turbomachinery was developed cooperatively with Integrated Fiber Optic Systems, Inc., and tested at the NASA Lewis Research Center. Because the probes are nearly flush with the casing inner lining, there is minimal flow disturbance. The two probes are closely spaced in a circumferential plane and are slanted at an angle relative to each other so that the time it takes the blade tip to traverse the space between the two beams varies with the tip radius, making it possible to determine the tip clearance at rotor operating conditions. The tip clearance can be obtained for all the blades in a rotor with a single system, provided there are no synchronous vibrations present at a particular operating condition. The two probes for the laser system were installed in two holders. For one, the included angle between the probes was 20 degrees, and for the other, it was 40 degrees. The two configurations were calibrated in a vacuum spin-rig facility that can reproduce realistic blade-tip speeds. A specially designed, nondeflecting rotor was used to calibrate the probes. This rotor consisted of a tapered titanium bar with three teeth on each end, the thickness of which was representative of a typical blade-tip thickness. The bar and measuring teeth were in a horizontal plane in the spin rig, and the axis of rotation was vertical. To set the clearances, we used a remotely controlled optical stage that could be traversed vertically. The 40 probe system also was used to measure the tip clearance during an engine fan prototype test in a wind tunnel. Using the spin-rig calibrations, we estimated the accuracy of the tip-clearance measurement in the test to be 0.005 in. This program is ongoing.

Dhadwal, Harbans S.↗

NASA NTRS2015

Space Qualification of the Optical Filter Assemblies for the ICESat-2/ATLAS Instrument

The Advanced Topographic Laser Altimeter System (ATLAS) will be the only instrument on the Ice, Cloud, and Land Elevation Satellite -2 (ICESat-2). ICESat-2 is the 2nd-generation of the orbiting laser altimeter ICESat, which will continue polar ice topography measurements with improved precision laser-ranging techniques. In contrast to the original ICESat design, ICESat-2 will use a micro-pulse, multi-beam approach that provides dense cross-track sampling to help scientists determine a surface's slope with each pass of the satellite. The ATLAS laser will emit visible, green laser pulses at a wavelength of 532 nm and a rate of 10 kHz and will be split into 6 beams. A set of six identical, thermally-tuned etalon filter assemblies will be used to remove background solar radiation from the collected signal while transmitting the laser light to the detectors. A seventh etalon assembly will be used to monitor the laser center wavelength during the mission. In this paper, we present the design and optical performance measurements of the ATLAS optical filter assemblies (OFA) in air and in vacuum before integration on the ATLAS instrument.

Etalons↗

NASA NTRS1978

Correlation of laser velocimeter measurements over a wing with results of two prediction techniques

The flow field at the center line of an unswept wing with an aspect ratio of eight was determined using a two dimensional viscous flow prediction technique for the flow field calculation, and a three dimensional potential flow panel method to evaluate the degree of two dimensionality achieved at the wing center line. The analysis was made to provide an acceptable reference for comparison with velocity measurements obtained from a fringe type laser velocimeter optics systems operating in the backscatter mode in the Langley V/STOL tunnel. Good agreement between laser velocimeter measurements and theoretical results indicate that both methods provide a true representation of the velocity field about the wing at angles of attack of 0.6 and 4.75 deg.

Hoad, D. R.↗

NASA NTRS1990

NGC 4438: Ram pressure sweeping of a tidally disrupted galaxy

NGC 4438 is the highly HI deficient peculiar spiral in the center of the Virgo cluster. Observations are given of the neutral hydrogen emission obtained with the Very Large Array (VLA) in the D-array configuration. These observations map out the total HI as determined from single dish measurements, and show the hydrogen to be confined to a region about one third the size of the optical disk and displaced to the side of the galaxy opposite M87. The hydrogen content of the galaxy is over an order of magnitude less than that expected for a galaxy of its type. The data suggest that the HI deficiency is a result of ram pressure stripping of the gas in the outer regions of the galaxy by the hot intracluster medium after being tidally perturbed.

Hibbard, J. E.↗

NASA NTRS1993

Honeywell's Compact, Wide-angle Uv-visible Imaging Sensor

Honeywell is currently developing the Earth Reference Attitude Determination System (ERADS). ERADS determines attitude by imaging the entire Earth's limb and a ring of the adjacent star field in the 2800-3000 A band of the ultraviolet. This is achieved through the use of a highly nonconventional optical system, an intensifier tube, and a mega-element CCD array. The optics image a 30 degree region in the center of the field, and an outer region typically from 128 to 148 degrees, which can be adjusted up to 180 degrees. Because of the design employed, the illumination at the outer edge of the field is only some 15 percent below that at the center, in contrast to the drastic rolloffs encountered in conventional wide-angle sensors. The outer diameter of the sensor is only 3 in; the volume and weight of the entire system, including processor, are 1000 cc and 6 kg, respectively.

Pledger, D.↗

NASA NTRS1999

Portable Inspection

The portable SpectroReflectometer, an instrument developed by AZ Technology, Inc. in partnership with NASA's Kennedy Space Center is now being manufactured and sold as a cost-effective solution to the development of scientific space flight hardware. This technology originated with the efforts to determine the degradation mechanisms of the space environment on space craft materials. AZ Technology's mission is to provide high quality products and services in electro-mechanical-optical design and hardware integration, advanced thermal and optical coatings and materials, and in the development of custom hardware systems for scientific measurements.

Source record↗

NASA NTRS2007

SIM Planetquest Science and Technology: A Status Report

Optical interferometry will open new vistas for astronomy over the next decade. The Space Interferometry Mission (SIM-PlanetQuest), operating unfettered by the Earth's atmosphere, will offer unprecedented astrometric precision that promises the discovery of Earth-analog extra-solar planets as well as a wealth of important astrophysics. Results from SIM will permit the determination of stellar masses to accuracies of 2% or better for objects ranging from brown dwarfs through main sequence stars to evolved white dwarfs, neutron stars, and black holes. Studies of star clusters will yield age determinations and internal dynamics. Microlensing measurements will present the mass spectrum of the Milky Way internal to the Sun while proper motion surveys will show the Sun's orbital radius and speed. Studies of the Galaxy's halo component and companion dwarf galaxies permit the determination of the Milky Way's mass distribution, including its Dark Matter component and the mass distribution and Dark Matter component of the Local Group. Cosmology benefits from precision (1-2%) determination of distances to Cepheid and RR Lyrae standard candles. The emission mechanism of supermassive black holes will be investigated. Finally, radio and optical celestial reference frames will be tied together by an improvement of two orders of magnitude. Optical interferometers present severe technological challenges. The Jet Propulsion Laboratory, with the support of Lockheed Martin Advanced Technology Center (LM ATC) and Northrop Grumman Space Technology (NGST), has addressed these challenges with a technology development program that is now complete. The requirements for SIM have been satisfied, based on outside peer review, using a series of laboratory tests and appropriate computer simulations: laser metrology systems perform with 10 picometer precision; mechanical vibrations have been controlled to nanometers, demonstrating orders of magnitude disturbance rejection; and knowledge of component positions throughout the whole test assembly has been demonstrated to the required picometer level. Technology transfer to the SIM flight team is now well along.

astrometry↗

NASA NTRS2009

Reflectance Spectra Comparison of Orbital Debris, Intact Spacecraft, and Intact Rocket Bodies in the GEO Regime

A key objective of NASA s Orbital Debris program office at Johnson Space Center (JSC) is to characterize the debris environment by way of assessing the physical properties (type, mass, density, and size) of objects in orbit. Knowledge of the geosynchronous orbit (GEO) debris environment in particular can be used to determine the hazard probability at specific GEO altitudes and aid predictions of the future environment. To calculate an optical size from an intensity measurement of an object in the GEO regime, a 0.175 albedo is assumed currently. However, identification of specific material type or types could improve albedo accuracy and yield a more accurate size estimate for the debris piece. Using spectroscopy, it is possible to determine the surface materials of space objects. The study described herein used the NASA Infrared Telescope Facility (IRTF) to record spectral data in the 0.6 to 2.5 micron regime on eight catalogued space objects. For comparison, all of the objects observed were in GEO or near-GEO. The eight objects consisted of two intact spacecraft, three rocket bodies, and three catalogued debris pieces. Two of the debris pieces stemmed from Titan 3C transtage breakup and the third is from COSMOS 2054. The reflectance spectra of the Titan 3C pieces share similar slopes (increasing with wavelength) and lack any strong absorption features. The COSMOS debris spectra is flat and has no absorption features. In contrast, the intact spacecraft show classic absorption features due to solar panels with a strong band gap feature near 1 micron. The two spacecraft are spin-stabilized objects and therefore have solar panels surrounding the outer surface. Two of the three rocket bodies are inertial upper stage (IUS) rocket bodies and have similar looking spectra. The slopes flatten out near 1.5 microns with absorption features in the near-infrared that are similar to that of white paint. The third rocket body has a similar flattening of slope but with fewer features of white paint - indicating that the surface paint on the SL-12 may be different than the IUS. This study shows that the surface materials of debris appear different spectrally than intact rocket bodies and spacecraft and therefore are not believed to be solar panel material or pristine white paint. Further investigation is necessary in order to eliminate materials as possible choices for the debris pieces.

Barker, Ed↗

NASA NTRSDate not supplied

Studying Microbial Adaptation in the Laboratory: Sensor & Control Upgrades for an Experimental Evolution Biofluidics System

Experimental evolution (EE) involves iteratively exposing a microbial community to specific stressors to study its response to changes in environment over time. EE work is commonly done manually in the laboratory, but, when there are many environmental variables to measure and adjust, it is highly labor intensive, prone to human error, and challenging to scale. Single-purpose automated continuous culturing chambers exist, but implement only limited stressor types. A more general-purpose design is desirable. The BeING Lab at Ames Research Center created the prototype Automated Adaptive Directed Evolution Chamber (AADEC) to address these problems, beginning with Escherichia coli tolerance of short-wave ultraviolet (UV-C) radiation and of temperature. In newer versions, AADEC monitors microbial activity and can adjust the UV-C and temperature levels automatically. An optical density measurement is used to determine how many cells are present in the growth medium—over time, this corresponds to how many survive and reproduce. Oxidation-reduction potential provides information on consumed metabolic energy, and pH and electrical conductivity on metabolic products. Dissolved oxygen content is used to determine aerobic vs anaerobic growth. A Raspberry Pi computer processes all this data to set the UV-C stressor level. AADEC’s auxiliary systems include peristaltic pumps to change media and agitation to counteract cell settling. These actuators can also act as additional stressors. With the Raspberry Pi monitoring sensors and adjusting actuators in real time, AADEC takes measurements and controls the environment much more accurately than can be done with a manual EE implementation. The third and latest AADEC iteration is the first to simplify design and usage with circuits on PCBs and the ability to pre-program experimental protocols. Still planned is expansion to a multi-well design for the study of varying cell cultures in parallel, which will enable researchers to retain and re-inoculate cultures exhibiting the desired trait most strongly while flushing out others. AADEC’s special capabilities make it a valuable tool for studying life under multiple stressors, enabling scientists to replicate changes in climate on microbes for study in a lab setting.

Microbial Adaptation↗

NASA NTRS1998

Optical Sensor/Actuator Locations for Active Structural Acoustic Control

Researchers at NASA Langley Research Center have extensive experience using active structural acoustic control (ASAC) for aircraft interior noise reduction. One aspect of ASAC involves the selection of optimum locations for microphone sensors and force actuators. This paper explains the importance of sensor/actuator selection, reviews optimization techniques, and summarizes experimental and numerical results. Three combinatorial optimization problems are described. Two involve the determination of the number and position of piezoelectric actuators, and the other involves the determination of the number and location of the sensors. For each case, a solution method is suggested, and typical results are examined. The first case, a simplified problem with simulated data, is used to illustrate the method. The second and third cases are more representative of the potential of the method and use measured data. The three case studies and laboratory test results establish the usefulness of the numerical methods.

Piezoelectric actuators↗

NASA NTRS1993

Long-period oxygen-rich optical Miras in the solar neighborhood

The spatial distribution of the oxygen-rich Miras with periods longer than 400 days in the neighborhood of the sun were determined using available survey and the K-band period luminosity relationship. It is found that the exponential scale height of these stars is near 240 pc. There is a marked contrast between the Mira population at about 1 kpc from the Galactic center where there are nearly as many long-period oxygen-rich Miras as intermediate-period oxygen-rich Miras. It is hypothesized that, at about 1 kpc from the Galactic center, the main sequence stars with masses larger than 1 solar mass have higher metallicities than main-sequence stars with the same masses in the solar neighborhood. In the solar neighborhood such main sequence stars become carbon-rich on the AGB and in the region near the Galactic center they become long-period oxygen-rich Miras.

Jura, M.↗

NASA NTRS1983

A GTD study of pyramidal horns for offset reflector antenna applications

An efficient computational method is demonstrated for determining the far-field patterns of reflectors illuminated by pyramidal horns. A uniform geometrical theory of diffraction (GTD) formulation is used to determine the near- and far-fields of the horn. The far-field patterns of the offset reflector are constructed using the physical optics (PO) formulation in conjunction with the Jacobi-Bessel expansion method. Many representative results are shown for the far-field patterns of the reflector. In particular, the concept of the optimum phase center for the best location of a horn illuminating a reflector is carefully studied and some useful observations are made.

Huang, J.↗

NASA NTRS1990

The 27-28 October 1986 FIRE IFO cirrus case study - Cloud optical properties determined by High Spectral Resolution Lidar

The High Spectral Resolution Lidar (HSRL) was operated from a roof-top site in Madison, Wisconsin. The transmitter configuration used to acquire the case study data produces about 50 mW of ouput power and achieved eye-safe, direct optical depth, and backscatter cross section measurements with 10 min averaging times. A new continuously pumped, injection seeded, frequency doubled Nd:YAG laser transmitter reduces time-averaging constraints by a factor of about 10, while improving the aerosol-molecular signal separation capabilities and wavelength stability of the instrument. The cirrus cloud backscatter-phase functions have been determined for the October 27-28, 1986 segment of the HSRL FIRE dataset. Features exhibiting backscatter cross sections ranging over four orders of magnitude have been observed within this 33 h period. During this period, cirrus clouds were observed with optical thickness ranging from 0.01 to 1.4. The altitude relationship between cloud top and bottom boundaries and the optical center of the cloud is influenced by the type of formation observed.

Grund, C. J.↗

NASA NTRS1995

Study of Luminescence Characteristics of Trivalent Terbium in Silicate Glass

An important use of silicate glasses doped with terbium oxide (Tb2O3) is their use as fiber optic sensors for high-resolution imaging applications requiring the detection of x-rays (e.g. tomography and radiography). The x-ray radiation is absorbed by the glass, producing electron-hole pairs (excitons). The excitons migrate through the glass matrix and then recombine, emitting characteristic Tb(3+) luminescence in the optical wavelength region. This emission is due to forbidden transitions of 4f electrons and therefore has a long decay time. Long decay time is undesirable when imaging transient events since it results in blurring in time of the images. It has been reported elsewhere that in crystals Tb(3+) ions can act both as luminescence centers and as fluorescence traps. These traps can capture excitons and delay their recombination. This delayed fluorescence is seen as a long lived, secondary component to the luminescence decay curve, or afterglow. Such a secondary decay component to the luminescence decay of Tb(3+) has been observed before in soda glass following pulsed optical excitation. In order to determine the conditions under which afterglow occurs, an understanding of the material's luminescent properties is required.

West, Mike S.↗

NASA NTRS2006

Electronic Absolute Cartesian Autocollimator

An electronic absolute Cartesian autocollimator performs the same basic optical function as does a conventional all-optical or a conventional electronic autocollimator but differs in the nature of its optical target and the manner in which the position of the image of the target is measured. The term absolute in the name of this apparatus reflects the nature of the position measurement, which, unlike in a conventional electronic autocollimator, is based absolutely on the position of the image rather than on an assumed proportionality between the position and the levels of processed analog electronic signals. The term Cartesian in the name of this apparatus reflects the nature of its optical target. Figure 1 depicts the electronic functional blocks of an electronic absolute Cartesian autocollimator along with its basic optical layout, which is the same as that of a conventional autocollimator. Referring first to the optical layout and functions only, this or any autocollimator is used to measure the compound angular deviation of a flat datum mirror with respect to the optical axis of the autocollimator itself. The optical components include an illuminated target, a beam splitter, an objective or collimating lens, and a viewer or detector (described in more detail below) at a viewing plane. The target and the viewing planes are focal planes of the lens. Target light reflected by the datum mirror is imaged on the viewing plane at unit magnification by the collimating lens. If the normal to the datum mirror is parallel to the optical axis of the autocollimator, then the target image is centered on the viewing plane. Any angular deviation of the normal from the optical axis manifests itself as a lateral displacement of the target image from the center. The magnitude of the displacement is proportional to the focal length and to the magnitude (assumed to be small) of the angular deviation. The direction of the displacement is perpendicular to the axis about which the mirror is slightly tilted. Hence, one can determine the amount and direction of tilt from the coordinates of the target image on the viewing plane.

Leviton, Douglas B.↗

NASA NTRS1998

Injector Mixing Efficiency Experiments

Various optical diagnostic techniques such as laser induce fluorescence, Raman spectroscopy, laser Doppler velocimetry, and laser light scattering have been employed to study the flowfield downstream of a single injector element in a optically accessible rocket chamber at Penn State for a number o years. These techniques have been used with both liquid and gaseous oxygen at pressures up to 1000 psia which is the limit of the facility. The purpose of the test programs at Penn State were to develop the techniques and to study the flow field from various injector designs. To extend these studies to higher pressure and ultimately to multiple injectors require the capabilities of the Marshall Space Flight Center. These studies will extend the data base available for the various injector designs to higher pressure as well as to determine the interaction between multiple injectors. During this effort the Princeton Instruments ICCD camera was set up and checked out. The functionality of the system has been thoroughly checked and the shutter compensation time was found to be not working. The controller was returned to the manufacturer for warranty repair. The sensitivity has been measured and found to be approximately 60 counts per photon at maximum gain which agrees with the test data supplied by the manufacturer. The actual value depends on wavelength. The Princeton Instruments camera was been installed in a explosion proof tube for use with the rocket combustor. A 35 mm camera was also made ready for taking still photos inside the combustor. A fiber optic was used to transmit the laser light from an argon-ion laser to the rocket combustor for the light scattering images. This images were obtained for a LOX-hydrogen swirl coax injector. Several still photos were also obtained with the 35 mm camera for these firings.

Moser, Marlow D.↗