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At least 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Particle track record of Apollo 15 shocked crystalline rocks

Cosmic ray track densities in two mare basalts 15058 and 15555 are multivalued at each depth from the surface, and numerous indications of shock are present, suggesting that shock has lowered track densities in some crystals but not in others. From the minimum track densities, the maximum time since the last shock event is derived for each rock. In separate observations 15017, a black glass, has a surface age of about 14,000 years derived from impact pits, but because of low track retentivity a solar flare record of only 1 year.

Fleischer, R. L.↗
NASA NTRS1973

Cosmic ray track production rates in lunar materials

A particularly favorable rock from the Apollo 16 mission (68815) has been used to derive an 'empirical track production energy spectrum' suitable for calculating track exposure ages from galactic cosmic rays in lunar materials. The spectrum is a long term average for the last 2m.y. and is independent of assumptions about the detailed nature of track registration in lunar minerals. The spectrum is close to that previously estimated from measurements of contemporary cosmic rays and does not support the recent suggestion that track exposure ages should be revised upwards.

Walker, R.↗
NASA NTRS1974

The accuracy of automatic tracking

It has been generally assumed that tracking accuracy changes similarly to the rate of change of the curve of the measurement conversion. The problem that internal noise increases along with the signals processed by the tracking device and that tracking accuracy thus drops were considered. The main prerequisite for solution is consideration of the dependences of the output signal of the tracking device sensor not only on the measured parameter but on the signal itself.

Kastrov, V. V.↗
NASA NTRS1975

Tracking performance under time sharing conditions with a digit processing task: A feedback control theory analysis

A one dimensional compensatory tracking task and a digit processing reaction time task were combined in a three phase experiment designed to investigate tracking performance in time sharing. Adaptive techniques, elaborate feedback devices, and on line standardization procedures were used to adjust task difficulty to the ability of each individual subject and manipulate time sharing demands. Feedback control analysis techniques were employed in the description of tracking performance. The experimental results show that when the dynamics of a system are constrained, in such a manner that man machine system stability is no longer a major concern of the operator, he tends to adopt a first order control describing function, even with tracking systems of higher order. Attention diversion to a concurrent task leads to an increase in remnant level, or nonlinear power. This decrease in linearity is reflected both in the output magnitude spectra of the subjects, and in the linear fit of the amplitude ratio functions.

Gopher, D.↗
NASA NTRS1975

Performance evaluation of tracking based on a low pass filter model

The performance of a human in a closed loop tracking task can be determined by using a simple low pass filter model with a least squares identification algorithm. The crossover model and the extended crossover model can be shown to be special cases of the low pass filter model presented here. Performance in tracking can be easily determined by mean square tracking error which can be written in terms of the parameters of the low pass filter model. A closed form expression for the effective time delay is also obtained. Experimental data from a roll axis tracking simulation is presented and simple prediction rules are determined. A comparison is made between this model and the crossover model with respect to their differences and similarities.

Repperger, D. W.↗
NASA NTRS1975

Effects of control-stick parameters on tracking performance in a vibration environment

A set of manual control experiments was conducted to determine the effects of control stick parameters on tracking performance in a vibration environment. Primary experimental variables were stick design parameters, stick location, and presence or absence of vibration. Considerable effect on control activity suggests that stick design parameters will significantly influence overall performance in systems that respond at vibration frequencies. Stick location had no significant effect on either tracking or biodynamic performance measures. The vibration correlated component of tracking error was relatively small. A model based guide for the design of control sticks in a vibration environment is described. This model is based on the state variable model for pilot/vehicle systems. Effects of vibration are represented as additional model elements and by changes in pilot related parameters of the tracking model.

Levison, W. H.↗
NASA NTRS1975

The evolution of the Tracking and Data Relay Satellite System /TDRSS/

Certain limitations of a ground-based network of remote tracking stations for communications with spacecraft are to be overcome by making use of a space-based network. Studies related to the development of a Tracking and Data Relay Satellite System (TDRSS) are discussed. The TDRSS is to function as an integral part of the post-1980 NASA Spaceflight Tracking and Data Network (STDN). The TDRSS will consist of two operational Tracking and Data Relay (TDR) spacecraft separated by at least 130 deg in longitude. According to current planning, the STDN will also include five ground-based sites, for support of users with orbital altitudes greater than approximately 2000 km, and two launch support sites.

Godfrey, R. D.↗
NASA NTRS1976

Viking 1 planetary phase tracking operations: Mars orbit insertion through landing

This article describes tracking operations during the Viking 1 planetary phase. Particular attention is paid to special planning for critical phase tracking operations, and to the degree of success subsequently achieved by these special plans during the actual operations. In-depth coverage is provided for Mars orbit insertion (MOI), periapsis passage tracking, and Lander direct links. The article concludes that on balance, tracking operations during the Viking 1 planetary phase have been effectively implemented and quite successful.

Berman, A. L.↗
NASA NTRS1977

Tracking and data system support for the Viking 1975 mission to Mars. Volume 1: Prelaunch planning, implementation, and testing

The tracking and data acquisition support for the 1975 Viking Missions to Mars is described. The history of the effort from its inception in late 1968 through the launches of Vikings 1 and 2 from Cape Kennedy in August and September 1975 is given. The Viking mission requirements for tracking and data acquisition support in both the near earth and deep space phases involved multiple radar tracking and telemetry stations, and communications networks together with the global network of tracking stations, communications, and control center. The planning, implementation, testing and management of the program are presented.

Mudgway, D. J.↗
NASA NTRS1977

Acoustic tracking of woodhead seabed drifters

An investigation was conducted to determine the feasibility of tracking Woodhead seabed drifters that were instrumented with miniature acoustic transmitters having a range in water in excess of 1.0 n.mi. A trial cruise at the entrance of Delaware Bay, with the R.V. Annandale as the sonar-tracking vessel, verified acoustic communications and positioning of the bottom drifters. A demonstration cruise with the R.V. Annandale was also performed in the New York Bight to attempt to collect information on bottom water movement near the sewage-sluge dump site. Results from the tracking mission in the New York Bight suggested that bottom water currents were negligible near the dump site during the time interval from November 7-12, 1975, and that shipboard sonar tracking of acoustic Woodhead seabed drifters could provide useful Lagragian information on bottom water movement caused by tidal and other nonstorm effects.

Mayhue, R. J.↗
NASA NTRS1977

Implantable acoustic-beacon automatic fish-tracking system

A portable automatic fish tracking system was developed for monitoring the two dimensional movements of small fish within fixed areas of estuarine waters and lakes. By using the miniature pinger previously developed for this application, prototype tests of the system were conducted in the York River near the Virginia Institute of Marine Science with two underwater listening stations. Results from these tests showed that the tracking system could position the miniature pinger signals to within + or - 2.5 deg and + or - 135 m at ranges up to 2.5 km. The pingers were implanted in small fish and were successfully tracked at comparable ranges. No changes in either fish behavior or pinger performance were observed as a result of the implantation. Based on results from these prototype tests, it is concluded that the now commercially available system provides an effective approach to underwater tracking of small fish within a fixed area of interest.

Mayhue, R. J.↗
NASA NTRS1976

On the nature of the radial and cross track errors for artificial earth satellites

The paper discusses the analysis of the radial and cross track errors of artificial earth satellites in terms of the interference of two one-dimensional celestial mechanical wave trains. The resulting equations for these tracking errors describe the behavior of the uncertainties in the orbital parameters as oscillatory in nature, with a rapidly oscillating term, which is a function of the sum of the observed and computed orbital frequencies, modulated in amplitude by a slowly varying oscillation. This latter term is itself a function of either the difference between these orbital frequencies or between the values of the computed and observed right ascensions, depending upon whether it is the radial or cross track case under consideration. Results indicate that the cross track calculation describes the behavior of uncertainties in the right ascension of the ascending node and the inclination, while the radial calculation gives information on uncertainties in the semi-major axis, the eccentricity, and the argument of perigee.

Bonavito, N. L.↗
NASA NTRS1976

The human operator in manual preview tracking /an experiment and its modeling via optimal control/

A manual preview tracking experiment and its results are presented. The preview drastically improves the tracking performance compared to zero-preview tracking. Optimal discrete finite preview control is applied to determine the structure of a mathematical model of the manual preview tracking experiment. Variable parameters in the model are adjusted to values which are consistent to the published data in manual control. The model with the adjusted parameters is found to be well correlated to the experimental results.

Tomizuka, M.↗
NASA NTRS1978

System and method for tracking a signal source

A system for tracking moving signal sources is disclosed which is particularly adaptable for use in tracking stage performers. A miniature transmitter is attached to the person or object to be tracked and emits a detectable signal of a predetermined frequency. A plurality of detectors positioned in a preset pattern sense the signal and supply output information to a phase detector which applies signals representing the angular orientation of the transmitter to a computer. The computer provides command signals to a servo network which drives a device such as a motor driven mirror reflecting the beam of a spotlight, to track the moving transmitter.

Mogavero, L. N.↗
NASA NTRS1977

A low cost high temperature sun tracking solar energy collector

The design and economic evaluation of a low cost high temperature two axis sun tracking solar energy collector are described. The collector design is specifically intended for solar energy use with the freedom of motion about its two control axes being limited only to the amplitude required to track the sun. An examination of the performance criteria required in order to track the sun and perform the desired solar energy conversion is used as the starting point and guide to the design. This factor, along with its general configuration and structural aspect ratios, is the significant contributor to achieving low cost. The unique mechanical design allows the control system to counter wide tolerances that will be specified for the fabrication of the azimuth frame and perform within a small tracking error.

Perkins, G. S.↗
NASA NTRS1977

The linear Fresnel lens - Solar optical analysis of tracking error effects

Real sun-tracking solar concentrators imperfectly follow the solar disk, operationally sustaining both transverse and axial misalignments. This paper describes an analysis of the solar concentration performance of a line-focusing flat-base Fresnel lens in the presence of small transverse tracking errors. Simple optics and ray-tracing techniques are used to evaluate the lens solar transmittance and focal-plane imaging characteristics. Computer-generated example data for an f/1.0 lens indicate that less than a 1% transmittance degradation occurs for transverse errors up to 2.5 deg. In this range, solar-image profiles shift laterally in the focal plane, the peak concentration ratio drops, and profile asymmetry increases with tracking error. With profile shift as the primary factor, the ninety-percent target-intercept width increases rapidly for small misalignments, e.g., almost threefold for a 1-deg error. The analytical model and computational results provide a design base for tracking and absorber systems for the linear-Fresnel-lens solar concentrator.

Cosby, R. M.↗
NASA NTRS1976

Automatic electronic fish tracking system

A newly developed electronic fish tracking system to automatically monitor the movements and migratory habits of fish is reported. The system is aimed particularly at studies of effects on fish life of industrial facilities which use rivers or lakes to dump their effluents. Location of fish is acquired by means of acoustic links from the fish to underwater Listening Stations, and by radio links which relay tracking information to a shore-based Data Base. Fish over 4 inches long may be tracked over a 5 x 5 mile area. The electronic fish tracking system provides the marine scientist with electronics which permit studies that were not practical in the past and which are cost-effective compared to manual methods.

Osborne, P. W.↗
NASA NTRS1977

Nuclear track studies of the Pasamonte and Moore County eucrites

The selective annealing technique was applied to samples from the Pasamonte eucrite with a view to obtaining fission track ages of clasts in the meteorite. The method did not permit cosmic ray tracks to be distinguished from fission tracks in either Pasamonte or Moore County. A difference between the fossil track densities observed in an igneous clast and the surrounding host material appears to be due to a pre-irradiation on the Pasamonte parent planet.

Wilkening, L. L.↗