SEARCH · Engineering Papers

Results for “Tracking”

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 1,675 records · Page 93

All sources NASA NTRS DOE OSTI

NASA NTRS1984

Geosynchronous orbiter tracking by VLBI - Demonstration design

A demonstration has been designed to determine the three dimensional position of a satellite in geosynchronous earth orbit, with 5 meter accuracy, using tracking techniques based on very-long-base-line interferometry (VLBI). Two experiments are analyzed: the first uses tracking stations in California, Australia, and Guam, and the second uses stations in California, Australia, and Japan. Satellite VLBI observables are defined and measurement errors are predicted. Both experiments employ alternate observations between the satellite and extra-galactic radio sources to determine the satellite plane-of-sky position. Positional accuracy resulting from various combinations of data acquired over the satellite's orbital period is discussed. A strategy is devised for resolving integer cycle phase ambiguities, inherent in VLBI, without relying on an externally provided reference trajectory.

Border, J. S.↗

NASA NTRS1986

Tracking System for Infrared Spectrometer

Visible laser tracking system for infrared laser spectometer keeps probe infrared laser beam aimed at moving reflector, thereby keeping reflector image and return laser beam within spectrometer field of view. System includes tracking mirror tilted by stepping motors under microprocessor control to deflect beams toward continually changing reflector position.

Johnson, R. A.↗

NASA NTRS1984

Improved Carrier Tracking by Smoothing Estimators

Smoothing as a way to improve the carrier phase estimation is proposed and analyzed. The performance of first and second order Kalman optimum smoothers are investigated. This performance is evaluated in terms of steady state covariance error computation, dynamic tracking, and noise response. It is shown that with practical amounts of memory, a second order smoother can have a position error due to an acceleration or jerk step input less than any prescribed maximum. As an example of importance to the NASA Deep Space Network, a second order smoother can be used to track the Voyager spacecraft at Uranus and Neptune encounters with significantly better performance than a second order phase locked loop.

Raez, C. A. P.↗

NASA NTRS1984

Subjective Workload Assessment and Voluntary Control of Effort in a Tracking Task

A manual control tracking task was manipulated along two dimensions: (1) control order and (2) forcing function bandwidth. In the first phase of the experiment subjective workload assessments were collected. It was found that subjective assessments of workload were closely associated with performance in the case of increasing control order, but not in the case of increasing bandwidth. This was interpreted as indicating that subjective workload assessments are most appropriate for the study of increasing difficulty centered in response selection processes as opposed to response execution processes. In the second phase of the experiment the subjects were asked to voluntarily limit the effort they applied in the performance of the tracking task. The results indicate that the subjects were quite facile in doing this. However, comparison of these data to the findings of other studies that manipulated effort via dual-task biasing indicate that effort manipulation is much more potent in a single-task configuration. This finding is discussed in terms of multiple resource theories of attentional capacity. The utility of an analysis of covariance procedure in studying the relationships between subjective ratings and performance is highlighted.

Vidulich, M. A.↗

NASA NTRS1984

Types of Tracking Errors Induced by Concurrent Secondary Manual Task

Future one-man helicopters may require the pilot to control flight with one hand, and simultaneously manipulate other instruments using the other hand. The nature of errors induced in a right hand tracking task (simulating flight control) when responses are required by the left hand are examined. The present experiment focused on detection of hesitations in which the tracking joy stick remained motionless for 1/3 sec. or longer.

Klapp, S. T.↗

NASA NTRS1984

Stereo Electro-optical Tracking System (SETS)

The SETS is a remote, non-contacting, high-accuracy tracking system for the measurement of deflection of models in the National Transonic Facility at Langley Research Center. The system consists of four electronically scanned image dissector trackers which locate the position of Light Emitting Diodes embedded in the wing or body of aircraft models. Target location data is recorded on magnetic tape for later 3-D processing. Up to 63 targets per model may be tracked at typical rates of 1280 targets per second and to precision of 0.02mm at the target under the cold (-193 C) environment of the NTF tunnel.

Koenig, E. W.↗

NASA NTRS1984

Space Shuttle program communication and tracking systems interface analysis

The Space Shuttle Program Communications and Tracking Systems Interface Analysis began April 18, 1983. During this time, the shuttle communication and tracking systems began flight testing. Two areas of analysis documented were a result of observations made during flight tests. These analyses involved the Ku-band communication system. First, there was a detailed analysis of the interface between the solar max data format and the Ku-band communication system including the TDRSS ground station. The second analysis involving the Ku-band communication system was an analysis of the frequency lock loop of the Gunn oscillator used to generate the transmit frequency. The stability of the frequency lock loop was investigated and changes to the design were reviewed to alleviate the potential loss of data due the loop losing lock and entering the reacquisition mode. Other areas of investigation were the S-band antenna analysis and RF coverage analysis.

Dodds, J. G.↗

NASA NTRS1983

The ARGOS system used for tracking gray whales

The development of satellite whale tags used to track gray whales in the eastern north Pacific Ocean is summarized. Two gray whales were radio-tagged in San Ignacio Lagoon (Mexico) and tracked on their northbound migration. One of the transmitters was modified to record and relay depth-of-dive information at 15 sec intervals throughout the course of the dive. Technical elements of data acquisition and analysis are outlined. The major biological findings are discussed.

Mate, B. R.↗

NASA NTRS1984

Relative potentials of concentrating and two-axis tracking flat-plate photovoltaic arrays for central-station applications

The purpose of this study is to assess the relative economic potentials of concenrating and two-axis tracking flat-plate photovoltaic arrays for central-station applications in the mid-1990's. Specific objectives of this study are to provide information on concentrator photovoltaic collector probabilistic price and efficiency levels to illustrate critical areas of R&D for concentrator cells and collectors, and to compare concentrator and flat-plate PV price and efficiency alternatives for several locations, based on their implied costs of energy. To deal with the uncertainties surrounding research and development activities in general, a probabilistic assessment of commercially achievable concentrator photovoltaic collector efficiencies and prices (at the factory loading dock) is performed. The results of this projection of concentrator photovoltaic technology are then compared with a previous flat-plate module price analysis (performed early in 1983). To focus this analysis on specific collector alternatives and their implied energy costs for different locations, similar two-axis tracking designs are assumed for both concentrator and flat-plate options.

Borden, C. S.↗

NASA NTRS1985

Ultraheavy cosmic ray tracks in meteorites: A reappraisal, based on calibrations with relativistic ions

Experiments were carried out on tracks of high energy U ions in olivine, a common meteoritic mineral. The results offer an explanation for the lack of success of previous attempts to derive the Ultraheavy Cosmic Ray composition from the study of tracks in meteorites. They also suggest how such experiments should be performed. The methods tested are described and illustrated.

Perron, C.↗

NASA NTRS1985

SONTRAC: A solar neutron track chamber detector

The recent detection on the solar maximum mission (SMM) satellite of high energy neutrons emitted during large solar flares has provided renewed incentive to design a neutron detector which has the sensitivity, energy resolution, and time resolution to measure the neutron time and energy spectra with sufficient precision to improve our understanding of the basic flare processes. Over the past two decades a variety of neutron detectors has been flown to measure the atmospheric neutron intensity above 10 MeV and to search for solar neutrons. The SONTRAC (Solar Neutron Track Chamber) detector, a new type of neutron detector which utilizes n-p scattering and has a sensitivity 1-3 orders of magnitude greater than previous instruments in the 20-200 MeV range is described. The energy resolution is 1% for neutron kinetic energy, T sub n 50 MeV. When used with a coded aperture mask at 50 m (as would be possible on the space station) an angular resolution of approx. 4 arc sec could be achieved, thereby locating the sites of high energy nuclear interactions with an angular precision comparable to the existing x-ray experiments on SMM. The scintillation chamber is investigated as a track chamber for high energy physics, either by using arrays of scintillating optical fibers or by optical imaging of particle trajectories in a block of scintillator.

Frye, G. M., Jr.↗

NASA NTRS1984

Particle track measurements in lunar regolith breccias

Particle track measurements have been reported for 25 (5 percent) of the regolith breccias in the collection; they have been reported for 16 breccias (30 percent) in the reference suite. The most frequently reported measurement for these 25 breccias is the maximum surface exposure age of the compacted rock (48 percent of the published breccia measurements). Information on the nature of the precompaction regolith is given for 9 rocks (36 percent) and on the nature of the compaction event for 6 rocks (24 percent). Most of the breccias appear to have simple post-compaction surface exposure histories (89 percent). From the few track density frequency distributions (7) that are available and inferring from the low exposure ages of these rocks (75 percent were younger than 10 to the 6th years), it appears that most of these breccias are amenable to studies which separate the contemporary surface exposure age from information about the precompaction regolith. If the number of immature-submature precompaction soils (6 out of 10 of the breccias for which appropriate data are available) represents many regolith breccias, then we can infer that regolith breccias may sample the deeper, less reworked materials in the lunar soil and compliment the samples available from the returned cores.

Blanford, G. E.↗

NASA NTRS1984

Diagnosing the severe thunderstorm environment by mesoscale cloud tracking - A new approach and new information

A new method for cloud tracking and observing storm development using satellite imagery in a cloud relative mode is presented. This method changes the analyst's function to one of monitoring cloud growth and changes over a finite time period and identifying portions of the cloud that are suitable for use as trackers. It is shown how many problems previously encountered by meteorologists in mesoscale cloud tracking can be overcome by using the cloud relative technique to determine mesoscale flow fields whose heights are determined using stereographic techniques. By separating growth and decay from cloud motion in a cumulus field using the method and accurately defining cloud heights, vertical wind shears within mesoscale domains may be defined. When this information is used to study the relative velocity of flows at different levels with respect to a developing or mature storm, improved insight into storm behavior can be achieved.

Purdom, J. F. W.↗

NASA NTRS1985

Automatic crack propagation tracking

A finite element based approach to fully automatic crack propagation tracking is presented. The procedure presented combines fully automatic mesh generation with linear fracture mechanics techniques in a geometrically based finite element code capable of automatically tracking cracks in two-dimensional domains. The automatic mesh generator employs the modified-quadtree technique. Crack propagation increment and direction are predicted using a modified maximum dilatational strain energy density criterion employing the numerical results obtained by meshes of quadratic displacement and singular crack tip finite elements. Example problems are included to demonstrate the procedure.

Shephard, M. S.↗

NASA NTRS1985

Precision laser tracking for global and polar motion

This paper provides an overview of the Goddard Laser Tracking Network (GLTN). GLTN station locations, equipment, possible improvements, and data flow are discussed. Locations of the other major laser tracking networks and their present or expected performance are also provided. The material includes a listing of the Lunar Laser Ranging Stations (LLRSs) and their actual or expected performance.

Shawe, M. E.↗

NASA NTRS1985

GPS-based satellite tracking system for precise positioning

NASA is developing a Global Positioning System (GPS) based measurement system to provide precise determination of earth satellite orbits, geodetic baselines, ionospheric electron content, and clock offsets between worldwide tracking sites. The system will employ variations on the differential GPS observing technique and will use a network of nine fixed ground terminals. Satellite applications will require either a GPS flight receiver or an on-board GPS beacon. Operation of the system for all but satellite tracking will begin by 1988. The first major satellite application will be a demonstration of decimeter accuracy in determining the altitude of TOPEX in the early 1990's. By then the system is expected to yield long-baseline accuracies of a few centimeters and instantaneous time synchronization to 1 ns.

Yunck, T. P.↗

NASA NTRS1985

Tracking and disturbance rejection of MIMO nonlinear systems with PI controller

The tracking and disturbance rejection of a class of MIMO nonlinear systems with linear proportional plus integral (PI) compensator is studied. Roughly speaking, it is shown that if the given nonlinear plant is exponentially stable and has a strictly increasing dc steady-state I/O map, then a simple PI compensator can be used to yield a stable unity-feedback closed-loop system which asymptotically tracks reference inputs that tend to constant vectors and asymptotically rejects disturbances that tend to constant vectors.

Desoer, C. A.↗

NASA NTRS1985

Space Telescope moving target tracking

This paper formulates a Space Telescope (ST) moving target tracking algorithm and evaluates a practical implementation. The algorithm is shown to be satisfactory for tracking such moving objects as the moons of Mars.

Strikwerda, T. E.↗