SEARCH · Search NASA

Results for “alignment”

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 235 records · Page 13

All sources NASA NTRS DOE OSTI

NASA NTRS1988

Alignment verification procedures

In alignment verification procedures each laboratory is required to align its test machines and gripping fixtures to produce a nearly uniform tensile stress field on an un-notched sheet specimen. The blank specimens (50 mm w X 305 mm l X 2.3 mm th) supplied by the coordinators were strain gauged. Strain gauge readings were taken at all gauges (n = 1 through 10). The alignment verification procedures are as follows: (1) zero all strain gauges while specimen is in a free-supported condition; (2) put strain-gauged specimen in the test machine so that specimen front face (face 1) is in contact with reference jaw (standard position of specimen), tighten grips, and at zero load measure strains on all gauges. (epsilon sub nS0 is strain at gauge n, standard position, zero load); (3) with specimen in machine and at a tensile load of 10 kN measure strains (specimen in standard position). (Strain = epsilon sub nS10); (4) remove specimen from machine. Put specimen in machine so that specimen back face (face 2) is in contact with reference jaw (reverse position of specimen), tighten grips, and at zero load measure strains on all gauges. (Strain - epsilon sub nR0); and (5) with specimen in machine and at tensile load of 10 kN measure strains (specimen in reverse position). (epsilon sub nR10 is strain at gauge n, reverse position, 10 kN load).

Edwards, P. R.↗

NASA NTRS1989

Time-dependent modeling of field-aligned current-generated ion transients in the polar wind

The time evolution of field-aligned current-generated transient features in the high-latitude ionosphere is investigated. Ionospheric return currents generate significant downward heavy ion flows in the topside ionosphere with peak values well exceeding 10 to the 8th sq cm/s. When the return current ceases, the polar ionosphere rapidly returns to its previous equilibrium state. During the recovery phase of the return current event, an upward propagating heavy ion transient is formed, which is mainly characterized by a relatively short O(+) upwelling event. On the other hand, the H(+) escape flux remains relatively constant (within 10-20 percent) during field-aligned current events. It is also found that upward currents generate a transient heavy ion outflow, which exceeds the ambient H(+) escape flux by a factor of 3 to 5, depending on the duration and strength of the field-aligned current event.

Gombosi, T. I.↗

NASA NTRS1988

Spacecraft alignment estimation

A numerically well-behaved factorized methodology is developed for estimating spacecraft sensor alignments from prelaunch and inflight data without the need to compute the spacecraft attitude or angular velocity. Such a methodology permits the estimation of sensor alignments (or other biases) in a framework free of unknown dynamical variables. In actual mission implementation such an algorithm is usually better behaved than one that must compute sensor alignments simultaneously with the spacecraft attitude, for example by means of a Kalman filter. In particular, such a methodology is less sensitive to data dropouts of long duration, and the derived measurement used in the attitude-independent algorithm usually makes data checking and editing of outliers much simpler than would be the case in the filter.

Shuster, Malcolm D.↗

NASA NTRS1988

A method of gravity release compensation in the optical alignment of orbiting meteorological sounding and imaging instruments

This paper describes a method developed for precompensating the front-end (telescope) optical alignment of the Imager and Sounder radiometric instruments, which will be launched as components of the GOES I - M series of meteorological satellites. To satisfy the severe pointing accuracy requirements on these instruments, their alignments must be offset in the one - G field of the laboratory, in order that they will be correct in orbit. A method was developed to make the necessary alignment offset, using a counterweight mechanism; autocollimation returns from reference mirrors on the instrument structure and supporting fixturing provided feedback for adjusting the counterweight mechanism. A series of experiments was performed to verify that these autocollimation return measurements were a good predictor of telescope line-of-sight changes; these experiments are described and their results summarized.

Wetzel, James C.↗

NASA NTRS1989

Magnetosphere of Neptune - Auroral zone field-aligned potential drops?

This paper explores some possibilities for plasma populations, field-aligned currents, and field-aligned potentials in the magnetosphere of Neptune. Observed plasma populations at Saturn and Uranus may provide reasonable upper and low limits, respectively, to those at Neptune. Field-aligned current densities comparable to those at Earth may be observed by the Voyager magnetometer above Neptune's auroral zone. Inverted-V events reaching energies of several tens of keV may also be observed by the Voyager Low Energy Charged Particle experiment.

Cheng, Andrew F.↗

NASA NTRS1990

Quick Check Of Butt-Weld Alignment

Proposed tool measures alignments of plates before butt-welded. Provides nearly instantaneous check on alignment, thereby facilitating repetitive measurements along length of weld joint. Reduces risk of contamination of weld from dirty measuring tools. Middle photodetector indicates acceptable alignment when position of transmitter fiber preciously matches that of center receiver fiber. If plates offset, other photodetectors signal misalignment.

Smith, Matthew A.↗

NASA NTRS1990

Electrostatic lower hybrid waves excited by electromagnetic whistler mode waves scattering from planar magnetic-field-aligned plasma density irregularities

This paper presents a theoretical model for electrostatic lower hybrid waves excited by electromagnetic whistler mode waves propagating in regions of the magnetosphere and the topside ionosphere, where small-scale magnetic-field-aligned plasma density irregularities are thought to exist. In this model, the electrostatic waves are excited by linear mode coupling as the incident electromagnetic whistler mode waves scatter from the magnetic-field-aligned plasma density irregularities. Results indicate that high-amplitude short-wavelength (5 to 100 m) quasi-electrostatic whistler mode waves can be excited when electromagnetic whistler mode waves scatter from small-scale planar magnetic-field-aligned plasma density irregularities in the topside ionosphere and magnetosphere.

Bell, T. F.↗

NASA NTRS1989

Alignment mechanisms of paramagnetic grains revisited

Taking into account the tight coupling of grain axis with angular momentum due to effective dissipation of rotation energy, the alignment of spheroidal grains was investigated by paramagnetic relaxation. Alignment degree will be significantly improved in diffuse clouds. The inclusions of superparamagnetic (SPM) substances may play a key role in grain alignment in dark clouds as well as in diffuse clouds.

Seki, Munezo↗

NASA NTRS1991

Generation of field-aligned current in the auroral zone

Generation of a magnetic field-aligned current in the auroral zone connecting the magnetospheric and ionospheric plasmas has been studied by means of a three dimensional particle simulation model. The model is of a magnetostatic variety appropriate for a low beta plasma in which the high frequency transverse displacement current has been eliminated. The simulation model is highly elongated along the magnetic field lines in order to model a highly elongated flux tube in the auroral zone. An enhanced field-aligned current was generated by injection of a magnetospheric plasma across the auroral zone magnetic field at the center of the model. Such a plasma injection may correspond to a plasmoid injection at the geomagnetic tail associated with magnetic reconnection during a substorm or a transverse plasma flow along the low latitude magnetopause boundary layer. The results of the simulations show that the field-aligned current can be enhanced over the thermal current by a factor of 5 - 10 via such injection. Associated with the enhanced current are the electrostatic ion cyclotron waves and shear Alfven waves excited in the auroral zone.

Okuda, Hideo↗

NASA NTRS1992

Alignment of the atmospheric visibility monitoring telescope

Alignment of the first Atmospheric Visibility Monitoring Telescope has revealed errors in mount design, mount manufacture, software, and electronics. This article discusses error sources and solutions, and re-alignment results. Alignment requirements for operation are also presented. The telescope now operates with the desired accuracy and repeatability.

Cowles, K.↗

NASA NTRS1992

Optics Alignment Panel

The Optics Alignment Panel (OAP) was commissioned by the HST Science Working Group to determine the optimum alignment of the OTA optics. The goal was to find the position of the secondary mirror (SM) for which there is no coma or astigmatism in the camera images due to misaligned optics, either tilt or decenter. The despace position was reviewed of the SM and the optimum focus was sought. The results of these efforts are as follows: (1) the best estimate of the aligned position of the SM in the notation of HDOS is (DZ,DY,TZ,TY) = (+248 microns, +8 microns, +53 arcsec, -79 arcsec), and (2) the best focus, defined to be that despace which maximizes the fractional energy at 486 nm in a 0.1 arcsec radius of a stellar image, is 12.2 mm beyond paraxial focus. The data leading to these conclusions, and the estimated uncertainties in the final results, are presented.

Schroeder, Daniel J.↗

NASA NTRS1992

He(2+) in field-aligned beams - ISEE results

He(2+) concentrations are determined for 14 field-aligned proton-beam events observed in the ion-foreshock region upstream from the earth's bow shock by the ISEE spacecraft. For all 14 events, most under normal solar-wind conditions, the He(2+) concentrations were a factor of 10 or more below the H(+) concentrations in the field-aligned beams when normalized by the solar wind He(2+) to H(+) density ratio. These results indicate that field-aligned beams do not provide the principal He(2+) seed population for ion acceleration in the ion-foreshock region.

Fuselier, Stephen A.↗

NASA NTRS1993

Automated Alignment And Inspection Of Duct Welds

Machine vision system being developed for use in aligning ends of two round ducts before welding ends together and inspecting welded ducts for alignment after welding. System makes consistent, objective measurements quickly. Improves quality and reliability of welds, reduces need for rework, and reduces alignment and inspection time, thereby reducing cost of manufacture.

Cross, George S.↗

NASA NTRS1993

Algorithm Aligns Gyrocompass In Twisting And Swaying Vehicle

Algorithm proposed for use with strapdown inertial sensors synthesizes gyrocompass and repeatedly refines alignment of synthetic gyrocompass to maintain accuracy until time of departure. In original application, inertial sensors located in spacecraft twisting and swaying in wind on launching pad, and time of departure is time of launch. Also possible to devise terrestrial version of algorithm for use in aircraft, ground vehicle, or vessel. Algorithm includes local-level-navigator, coarse-alignment, and fine-alignment subalgorithms.

Reddy, Narotham S.↗

NASA NTRS1991

Efficient visual grasping alignment for cylinders

Monocular information from a gripper-mounted camera is used to servo the robot gripper to grasp a cylinder. The fundamental concept for rapid pose estimation is to reduce the amount of information that needs to be processed during each vision update interval. The grasping procedure is divided into four phases: learn, recognition, alignment, and approach. In the learn phase, a cylinder is placed in the gripper and the pose estimate is stored and later used as the servo target. This is performed once as a calibration step. The recognition phase verifies the presence of a cylinder in the camera field of view. An initial pose estimate is computed and uncluttered scan regions are selected. The radius of the cylinder is estimated by moving the robot a fixed distance toward the cylinder and observing the change in the image. The alignment phase processes only the scan regions obtained previously. Rapid pose estimates are used to align the robot with the cylinder at a fixed distance from it. The relative motion of the cylinder is used to generate an extrapolated pose-based trajectory for the robot controller. The approach phase guides the robot gripper to a grasping position. The cylinder can be grasped with a minimal reaction force and torque when only rough global pose information is initially available.

Nicewarner, Keith E.↗

NASA NTRS1993

Theory of grain alignment in molecular clouds

Research accomplishments are presented and include the following: (1) mathematical theory of grain alignment; (2) super-paramagnetic alignment of molecular cloud grains; and (3) theory of grain alignment by ambipolar diffusion.

Roberge, Wayne G.↗

NASA NTRS1991

Neural nets for aligning optical components in harsh environments: Beam smoothing spatial filter as an example

The goal is to develop an approach to automating the alignment and adjustment of optical measurement, visualization, inspection, and control systems. Classical controls, expert systems, and neural networks are three approaches to automating the alignment of an optical system. Neural networks were chosen for this project and the judgements that led to this decision are presented. Neural networks were used to automate the alignment of the ubiquitous laser-beam-smoothing spatial filter. The results and future plans of the project are presented.

Decker, Arthur J.↗

NASA NTRS1992

Efficient visual grasping alignment for cylinders

Nicewarner, Keith E.↗