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At least 1,567 records · Page 87

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NASA NTRS1974

ATS-F/GEOS-C satellite to satellite tracking data processing consideration

The satellite to satellite tracking data unique processing considerations are presented. The strategy to be employed in the application of data processing routines to the ATS-F/GEOS-C satellite to satellite tracking experiment is described. When these considerations are included, studies, analysis and simulations predict an orbital position uncertainty of less than 15 meters and a velocity uncertainty of less than 1.5 millimeters per second.

Bryan, J. W.↗

NASA NTRS1974

Error analysis for station position from tracking of the Lageos satellite

The earth physics satellite systems error analysis program was applied to the problem of predicting the relative accuracy of station position determinations under varying orbital and observing geometries. The reference case consists of nine ground stations extending over 1500 km which lasers ranged to a LAGEOS satellite, with simultaneous Doppler tracking from a geosynchronous satellite for 16 days. Eleven variations from the reference case were tested. The results showed little sensitivity to whether the LAGEOS altitude is 3700 or 5690 km. More significant were the high inclination, and that LAGEOS was tracked by a geosynchronous satellite.

Parmenter, M. E.↗

NASA NTRS1973

Tracking and data relay satellite system /TDRSS/

Plans for a new way of providing tracking and data acquisition support for future earth orbital missions, the Tracking and Data Relay Satellite System (TDRSS), are reviewed. This system is to become the principal support facility for all NASA R&D missions below about 5000 km altitude. Current plans call for a 2-satellite system that is to provide upwards of 85% coverage of all orbits above 200 km and 100% coverage above 1200 km.

Barritt, P. F.↗

NASA NTRS1974

Whole-rock uranium analysis by fission track activation

We report a whole-rock uranium method in which the polished sample and track detector are separated in a vacuum chamber. Irradiation with thermal neutrons induces uranium fission in the sample, and the detector records the integrated fission track density. Detection efficiency and geometric factors are calculated and compared with calibration experiments.

Weiss, J. R.↗

NASA NTRS1974

A tracking polarimeter for measuring solar and ionospheric Faraday rotation of signals from deep space probes

A tracking polarimeter implemented on the 64-m NASA/JPL paraboloid antenna at Goldstone, Calif., is described. Its performance is analyzed and compared with measurements. The system was developed to measure Faraday rotation in the solar corona of the telemetry carrier from the Pioneer VI spacecraft as it was occulted by the sun. It also measures rotation in the earth's ionosphere and is an accurate method of determining spacecraft orientation. The new feature of this system is its use of a pair of quarter-wave plates to allow the synthesis of a rotating feed system, while requiring the rotation of only a single section of waveguide. Since the polarization sensing is done at RF and the receiver operates essentially as a null detector, the system's accuracy is superior to other polarization tracking schemes. In addition, the antenna size and maser preamplifier provide unsurpassed sensitivity. The associated instrumentation used in the Pioneer VI experiment is also described.

Ohlson, J. E.↗

NASA NTRS1974

Conditioning of MVM '73 radio-tracking data

An extensive effort was undertaken to edit Mariner 10 radiometric tracking data. Interactive computer graphics were used for the first time by an interplanetary mission to detect blunder points and spurious signatures in the data. Interactive graphics improved the former process time by a factor of 10 to 20, while increasing reliability. S/X dual Doppler data was used for the first time to calibrate charged particles in the tracking medium. Application of the charged particle calibrations decreased the orbit determination error for a short data arc following the 16 March 1974 maneuver by about 80%. A new model was developed to calibrate the earth's troposphere with seasonal adjustments. The new model has a 2% accuracy and is 5 times better than the old model.

Koch, R. E.↗

NASA NTRS1972

Tracking the Lunar Rover vehicle with very long baseline interferometry techniques

The principles of operation of Very Long Baseline Interferometry (VLBI) are discussed. The application of VLBI techniques for tracking lunar rover vehicles during the Apollo 16 and 17 missions is reported. A map of the Apollo 16 lunar rover track is provided. Charts are developed to show the incremental motion of the lunar vehicle during the mission.

Shnidman, D.↗

NASA NTRS1975

Tracking techniques for space shuttle rendezvous

The space shuttle rendezvous radar has a requirement to track cooperative and non-cooperative targets. For this reason the Lunar Module (LM) Rendezvous Radar was modified to incorporate the capability of tracking a non-cooperative target. The modifications are discussed. All modifications except those relating to frequency diversity were completed, and system tests were performed to confirm proper performance in the non-cooperative mode. Frequency diversity was added to the radar and to the special test equipment, and then system tests were performed. This last set of tests included re-running the tests of the non-cooperative mode without frequency diversity, followed by tests with frequency diversity and tests of operation in the original cooperative mode.

Source record↗

NASA NTRS1975

Detailed requirements document for Stowage List and Hardware Tracking System (SLAHTS)

The stowage list and hardware tracking system, a computer based information management system, used in support of the space shuttle orbiter stowage configuration and the Johnson Space Center hardware tracking is described. The input, processing, and output requirements that serve as a baseline for system development are defined.

Keltner, D. J.↗

NASA NTRS1975

Recursive identification and tracking of parameters for linear and nonlinear multivariable systems

The problem of identifying constant and variable parameters in multi-input, multi-output, linear and nonlinear systems is considered, using the maximum likelihood approach. An iterative algorithm, leading to recursive identification and tracking of the unknown parameters and the noise covariance matrix, is developed. Agile tracking, and accurate and unbiased identified parameters are obtained. Necessary conditions for a globally, asymptotically stable identification process are provided; the conditions proved to be useful and efficient. Among different cases studied, the stability derivatives of an aircraft were identified and some of the results are shown as examples.

Sidar, M.↗

NASA NTRS1975

Microdosimetric structure of HZE particle tracks in tissue

Heavy nuclei of the primary galactic radiation in space can have the same linear energy transfer yet greatly different lateral distribution patterns of the energy in the microstructure of tissue. Track structure thus presents itself as a new dosimetric parameter for HZE particles which is at present incompletely understood in its radiobiological significance. The theory of track structure distinguishes two regions: core and penumbra. The core is a narrow region with a radius far below 1 micron in tissue where energy deposition occurs mainly through excitations and collective oscillations of electrons. Energy density in the core accounts for slightly more than half the total LET. The penumbra surrounding the core extends laterally several to many microns depending on the energy of the primary. Energy density in the penumbra decreases steeply with the square of increasing radius. The relationships are illustrated with nuclear emulsion micrographs and plots of energy density profiles. The implications of the findings for a dosimetric system for HZE particles are discussed.

Schaefer, H. J.↗

NASA NTRS1975

Functional design specification for Stowage List And Hardware Tracking System (SLAHTS)

This functional design specification defines the total systems approach to meeting the requirements stated in the Detailed Requirements Document for Stowage List and Hardware Tracking System for the space shuttle program. The stowage list and hardware tracking system is identified at the system and subsystem level with each subsystem defined as a function of the total system.

Keltner, D. J.↗

NASA NTRS1975

Human performance evaluation in dual-axis critical task tracking

A dual axis tracking using a multiloop critical task was set up to evaluate human performance. The effects of control stick variation and display formats are evaluated. A secondary loading was used to measure the degradation in tracking performance.

Ritchie, M. L.↗

NASA NTRS1974

The effect of spurious angular accelerations on tracking in dynamic simulation

A laboratory study was conducted to investigate the effect of spurious simulator yaw motions on a pilot's control performance. A second objective was to compare the efficiency of static and dynamic simulator tracking in previously unexamined vehicle dynamics. Twelve airline pilots served as subjects in a moving-base flight simulator under congruent-motion, spurious-motion, and no-motion conditions. The results indicated a significant increase in the amount of error with increasing levels of spurious motion during the initially administered series of trials. The influence of spurious motion, however, was absent in a second series of trials. The data suggest that the pilots learned to compensate in their performance for the spurious inputs. It was also found that congruent visual and rotational cueing produced superior performance to that of tracking with visual information alone.

Beck, L. J.↗

NASA NTRS1974

One way Doppler tracking for on-orbit navigation

The integration of Doppler frequencies extracted from S-band communication and tracking signals received onboard an orbiting spacecraft provides a means of navigating on-orbit. This paper describes the one way Doppler tracking concept and two mechanizations which are being investigated by the Johnson Space Center to determine a suitable one way Doppler extraction technique for the Space Shuttle Orbiter and other advanced space systems. The designs of two breadboard models are outlined and measurement errors are discussed.

Lamoreux, J. C.↗

NASA NTRS1975

Track view of the regolithic elephant

Information gained from track studies in lunar soils is reviewed. Soil maturity indices are compared and briefly discussed. Track methods to establish the layering chronology of lunar cores are also treated.

Crozaz, G.↗

NASA NTRS1977

Manchester transition tracking loop (MTTL)

In new tracking loop, separate phase detection algorithm is incorporated for acquisition; programmed acquisition-to-track sequence includes automatic bandwidth switching. Additionally, system has very effective phase detection signal-to-noise ratio and can operate at any rate by changing master clock frequency. All system parameters remain constant.

Cellier, A.↗

NASA NTRS1975

Fixed-base simulator study of the effect of time delays in visual cues on pilot tracking performance

Factors were examined which determine the amount of time delay acceptable in the visual feedback loop in flight simulators. Acceptable time delays are defined as delays which significantly affect neither the results nor the manner in which the subject 'flies' the simulator. The subject tracked a target aircraft as it oscillated sinusoidally in a vertical plane only. The pursuing aircraft was permitted five degrees of freedom. Time delays of from 0.047 to 0.297 second were inserted in the visual feedback loop. A side task was employed to maintain the workload constant and to insure that the pilot was fully occupied during the experiment. Tracking results were obtained for 17 aircraft configurations having different longitudinal short-period characteristics. Results show a positive correlation between improved handling qualities and a longer acceptable time delay.

Queijo, M. J.↗