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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.

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At least 289 records · Page 16
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NASA NTRS1972

Refinement of the gravity field by satellite-to-satellite Doppler tracking.

The question of what resolution of the gravity field can be obtained from satellite-to-satellite Doppler tracking was investigated by performing least-squares adjustments of simulated Doppler data, solving for parameters describing the anomalous gravity field in various sized blocks. By examining the correlation between the adjusted parameters describing neighboring blocks, it was possible to judge whether a given set of data was capable of resolving blocks of a given size. Two concepts of satellite-to-satellite tracking are considered: the first involves two satellites near together in very low orbits, while the second uses geostationary satellites to track a single very low satellite. In either case, blocks 500 km on a side can be satisfactorily resolved from an orbital altitude of 700 km. From an altitude of 200 km, blocks 200 km on a side can be resolved. Because of the lower limit on altitude imposed by the presence of the earth's atmosphere, it does not appear that satellite-to-satellite Doppler tracking will be able to resolve features smaller than 200 km on a side.

Schwarz, C. R.↗
NASA NTRS1973

Particle track record of Apollo 15 green soil and rock.

Track densities, track stability, and uranium contents have been measured in lunar samples containing abundant green glass spherules from stations 6a and 7 of the Apollo 15 mission. This glass is rather homogeneous in its track registration properties but nonuniform in its uranium content, specific gravity, and bulk etching rate. The major components of a soil sample, 15401, are found to have had an unusually short surface exposure (500,000 yr) and to have been stirred at least once, but not often during its lifetime. A nearby soil clod, 15426, appears to have been brought to the surface in the same event. 15405, the rock upon which 15401 was perched, has recorded deformation features and track densities compatible with its surface residence having begun at the same time.

Fleischer, R. L.↗
NASA NTRS1973

Particle track record in Apollo 15 deep core from 54 to 80 cm depths.

Particle track measurements have been made in nearly 500 individual grains from 13 levels in the 54-80 cm depth range of the Apollo 15 deep core. They reveal a wide range of track densities at all depths and some systematic variations within layers, indicating that both predepositional mixing and subsequent layering are present and that separate sublayers exist within larger regions where no sublayers are visible. Minimum track densities are inferred to be useful measures of maximum residence times for undisturbed layers. Using the observed minimum track densities, we conclude that the average deposition rate in this section of soil column was greater than 0.4 cm/million years.

Fleischer, R. L.↗
NASA NTRS1972

Tracking and data relay satellite system configuration and tradeoff study. Volume 1: TDRS system summary, part 1

A Tracking and Data Relay Satellite System (TDRSS) concept for service of low and medium data rate user spacecraft has been defined. The TDRS system uses two geosynchronous dual spin satellites compatible with Delta 2914 to provide command, tracking, and telemetry service between multiple low earth orbiting users and a centrally located ground station. The low data rate user service capability via each TDRS is as follows: (1) forward link at UHF: voice to one user, commands to 20 users (sequential), range and range rate service, and (2) return link at VHF: voice from one user, data from 20 users (simultaneous), range and range rate return signals. The medium data rate user service via each TDRS is as follows: (1) forward link at S band: voice or command and tracking signals to one user, and (2) return link at S band: voice, data and tracking signals from one user "order wire" for high priority service requests (implemented with an earth coverage antenna).

Source record↗
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.↗