Research study of a fundus tracker, phase 2 Final report 18 Jan. 1968 - 1 Feb. 1971
Development of apparatus for studying stabilized image properties of human eye using photomultiplier tube and magnetic core array storage system
Crane, H. D.↗
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The 1970 solar-tracker balloon flights, 3055, 3056, and 3057 Final report
High altitude solar cell and radiometer calibrations using balloon techniques
Conlon, R. D.↗
Input noise approximation in tracker modeling
The validity of approximating random Gaussian distributed inputs used in human response modeling by sums of discrete sine waves is studied. An ideal rectangular power density spectrum is simulated using both filtered Gaussian white noise and sums-of-discrete sine waves with three different input cutoff frequencies in the same compensatory tracking task. Resulting normalized tracking error and quality operator observations are used to investigate apparent discrepancies in human operator characteristics. Results show that discrete and continuous input tracking data compare favorable when the power in the crossover region is taken into account.
Torrey, P. F.↗
Refracting lens system for low-scatter star-tracker: A Concept
''Low Scatter Lens Design/Development'' discusses studies of low-scatter lens system. Two sections cover optical design and scattering analysis for model of lens system which rejects radiation. Result of computations are shown on computer printouts attached to report.
Source record↗
Automatic solar tracker
Mechanism uses differential pressure of condensable fluid against fixed piston to equalize radiant energy on pair of blackbody elements.
Conroy, B. L.↗
A computer-aided telescope pointing system utilizing a video star tracker
The Video Inertial Pointing (VIP) System developed to satisfy the acquisition and pointing requirements of astronomical telescopes is described. A unique feature of the system is the use of a single sensor to provide information for the generation of three axis pointing error signals and for a cathode ray tube (CRT) display of the star field. The pointing error signals are used to update the telescope's gyro stabilization and the CRT display is used by an operator to facilitate target acquisition and to aid in manual positioning of the telescope optical axis. A model of the system using a low light level vidicon built and flown on a balloon-borne infrared telescope is briefly described from a state of the art charge coupled device (CCD) sensor. The advanced system hardware is described and an analysis of the multi-star tracking and three axis error signal generation, along with an analysis and design of the gyro update filter, are presented. Results of a hybrid simulation are described in which the advanced VIP system hardware is driven by a digital simulation of the star field/CCD sensor and an analog simulation of the telescope and gyro stabilization dynamics.
Murphy, J. P.↗
Radar range data signal enhancement tracker
The design, fabrication, and performance characteristics are described of two digital data signal enhancement filters which are capable of being inserted between the Space Shuttle Navigation Sensor outputs and the guidance computer. Commonality of interfaces has been stressed so that the filters may be evaluated through operation with simulated sensors or with actual prototype sensor hardware. The filters will provide both a smoothed range and range rate output. Different conceptual approaches are utilized for each filter. The first filter is based on a combination low pass nonrecursive filter and a cascaded simple average smoother for range and range rate, respectively. Filter number two is a tracking filter which is capable of following transient data of the type encountered during burn periods. A test simulator was also designed which generates typical shuttle navigation sensor data.
Source record↗
Tracker implementation for the orbiter Ku-band communications antenna
Possible implementations and recommendations for the Space Shuttle Ku-Band integrated communications/radar antenna tracking system were evaluated. Communication aspects involving the Tracking Data Relay Satellite (TDRS)/Orbiter Ku-Band link are emphasized. Detailed analysis of antenna sizes, gains and signal-to-noise ratios shows the desirability of using maximum size 36-inch diameter dish and a triple channel monopulse. The use of the original baselined 20 inch dish is found to result in excessive acquisition time since the despread signal would be used in the tracking loop. An evaluation of scan procedures which includes vehicle dynamics, designation error, time for acquisition and probability of acquisition shows that the conical scan is preferred since the time for lock-on for relatively slow look angle rates will be significantly shorter than the raster scan. Significant improvement in spherical coverage may be obtained by reorienting the antenna gimbal to obtain maximum blockage overlap.
Rudnicki, J. F.↗
A computer-aided telescope pointing system utilizing a video star tracker
The Video Inertial Pointing (VIP) System is being developed to satisfy the acquisition and pointing requirements of astronomical telescopes. VIP employs a single video sensor to generate three-axis pointing error signals and to provide inputs for a cathode ray tube (CRT) display of the star field. The pointing error signals update the telescope's gyro stabilization system. The CRT display facilitates target acquisition and positioning of the telescope by a remote operator. The present paper describes the analysis, simulation, and hardware development of a prototype, advanced VIP system. An early model of the system utilizing a silicon-intensified target vidicon camera has flown on a balloon-borne telescope and is briefly described. The advanced system, which can employ either a vidicon camera or a charge-coupled device video sensor, has been tested using an analog/digital hybrid simulation. The advanced VIP hardware is described, and the simulation results presented.
Lorell, K. R.↗
Single-axle, double-axis solar tracker
Solar concentrator tracking mechanism consisting of angular axle and two synchronized drive motors, follows seasonal as well as diurnal changes in earth's orientation with respect to incoming sunlight.
Brantley, L. W.↗
Calibration of the Space Shuttle Microwave Scanning Beam Landing System using a laser tracker
Verification tests of the Space Shuttle Microwave Scanning Beam Landing System (MSBLS) performed with respect to the Precision Laser Tracking System are reported. MSBLS ground station measurements of the azimuth, elevation and range of a NASA Jetstar aircraft equipped with a laser retroreflector, a MSBLS antenna and commissioning instruments including a MSBLS navigation set of the type installed in the Orbiter, during the performance of radial, orbital and glideslope runs with respect to the ground station were compared with laser ground station measurements of aircraft position. Data obtained from flight testing at Shuttle landing sites reveal MSBLS distance measuring equipment performance to be very good, with elevation errors found at very low elevation angles and azimuth errors as a function of aircraft attitude. The Precision Laser Tracking System has thus proven to be a satisfactory instrument for determining MSBLS performance, and an ideal instrument for its calibration.
Ford, K.↗
Stereo electro-optical tracker study for the measurement of model deformations at the National Transonic Facility
The effects of model vibration, camera and window nonlinearities, and aerodynamic disturbances in the optical path on the measurement of target position is examined. Window distortion, temperature and pressure changes, laminar and turbulent boundary layers, shock waves, target intensity and, target vibration are also studied. A general computer program was developed to trace optical rays through these disturbances. The use of a charge injection device camera as an alternative to the image dissector camera was examined.
Hertel, R. J.↗
Attitude tracker
Line array sensors produce data which has no inherent geometrical continuity. Hence, any platform attitude variation will be evidenced as a distortion when the data lines are displayed in the normal Cartesian raster. Ancillary sensing is required to establish the platform attitude to allow geometric rectification. This is normally provided by inertial or star reference attitude sensors. However, in the absence of such sensors or if performance of them is degraded, the required attitude information is lost. A strawman sensor design is proposed which utilizes small image areas on the ground to provide a series of motion vectors with which the platform attitude can be tracked; this allows the distorted image received by the normal image line sensor to be rectified.
Billingsley, F. C.↗
Flight test evaluation of a video tracker for enhanced offshore airborne radar approach capability
As a part of NASA's Rotorcraft All-Weather Operations Research Program, advanced airborne radar approach (ARA) concepts are being investigated. Since data from previous NASA/FAA flight tests showed significant ARA limitations, a research program was initiated at NASA Ames Research Center to determine the benefit that could be derived by automating certain radar functions and superimposing course display data on the radar display. To evaluate these concepts, a newly developed video tracking system which interfaces with weather radar was acquired. After the pilot designates a destination target, the system tracks the target video as it moves on the radar indicator. Using a small, efficient microprocessor, the autotracker presents valuable approach data on the radar screen and automatically adjusts the radar gain and tilt. Results of a limited flight test evaluation of the autotracker show that the course display concept, combined with automated gain and tilt functions, is effective for improving ARA's and reducing radar operator workload.
Clary, G. R.↗
Eye-Movement Tracker Would Reduce Video Bandwidth
Bandwidth required to transmit closed circuit television image reduced by transmitting small portion at high resolution and remainder at low resolution. High-resolution portion centered in viewer's gaze so entire image seems to be of high resolution.
Ruoff, C. F.↗
Breadboard stellar tracker system test report
BASD has, in the past, developed several unique position tracking algorithms for charge transfer device (CTD) sensors. These algorithms provide an interpixel transfer function with the following characteristics: (1) high linearity; (2) simplified track logic; (3) high gain; and (4) high noise rejection. A previous test program using the GE charge injection device (CID) showed that accuracy for BASD's breadboard was limited to approximately 2% of a pixel (1 sigma) whereas analysis and simulation indicated the limit should be less than 0.5% of a pixel, assuming the limit to be detector response and dark current noise. The test program was conducted under NASA contract No. NAS8-34263. The test approach for that program did not provide sufficient data to identify the sources of error and left open the amount of contribution from parameters such as image distribution, geometric distortion and system alignment errors.
Kollodge, J. C.↗
Closed-form recursive formula for an optimal tracker with terminal constraints
Feedback control laws are derived for a class of optimal finite time tracking problems with terminal constraints. Analytical solutions are obtained for the feedback gain and the closed-loop response trajectory. Such formulations are expressed in recursive forms so that a real-time computer implementation becomes feasible. Two examples are given to illustrate the validity and usefulness of the formulations.
Juang, J.-N.↗