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  • 1
    Publication Date: 2019-06-27
    Description: A microcomputer which was developed to compute ground radio beacon position locations using satellite measurements of Doppler frequency shift is described. Both the computational algorithms and the microcomputer hardware incorporating these algorithms were discussed. Results are presented where the microcomputer in conjunction with the NIMBUS-6 random access measurement system provides real time calculation of beacon latitude and longitude.
    Keywords: LAUNCH VEHICLES AND SPACE VEHICLES
    Type: NASA-TM-78046
    Format: application/pdf
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  • 2
    Publication Date: 2019-06-27
    Description: An S-band tracking system employing one way Doppler applicable to the tracking and data relay system (TDRS) was evaluated. This evaluation is limited to the measurement system parameters. The analysis assumes state-of-the-art components such as spacecraft oscillator long term stability of one part in 10 to the 8th power and ground station oscillator stability of one part in 10 to the 11th power. Signal characteristics comparable with the present ranging systems are utilized in the analysis. Predicated upon measurement system parameters, position uncertainties for the low orbiting spacecraft vary from 5 meters to 2 kilometers along track, 4 meters to 1 kilometer cross track, and 1 meter to 180 meters radially depending upon the tracking geometry and the high satellite position and velocity error assumptions.
    Keywords: COMMUNICATIONS
    Type: NASA-TM-X-70526 , X-591-73-307
    Format: application/pdf
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  • 3
    Publication Date: 2019-06-27
    Description: The highly successful 24 hour trilateration tracking and orbit determination test conducted on 3 November 1974 is described. In this test a new method of accurately computing geostationary spacecraft orbits was applied to the Applications Technology Satellite (ats-6). A single tracking station interrogates several strategically deployed ground based transponders via the synchronous satellite whose orbit is to be determined. The ATS-6 tracking data measurement noise over the 24 hour period was observed to be 0.3 mm/sec in range rate and 1.5 meters in range. By means of overlap orbit computation using 2 separate tracking data bases, the ATS-6 total position and velocity uncertainties were determined to reach a minimum of 30 meters and 0.2 cm/sec respectively. The maximum position and velocity uncertainty over this same time period was determined to be approximately 250 meters and 2 cm/sec respectively. A position determination using simultaneous tracking of the NASA-GSFC site by ATS-6 and ATS-3 was also performed. Station location recovery was to an accuracy on the order of 100 meters over the first 10 hours of tracking.
    Keywords: SPACE COMMUNICATIONS, SPACECRAFT COMMUNICATIONS, COMMAND AND TRACKING
    Type: NASA-TM-X-70897 , X-932-75-104
    Format: application/pdf
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  • 4
    Publication Date: 2019-06-28
    Description: Ground-based microcomputer determines geographical positions of beacons using Doppler data from weather satellites. System requires onnly 7 W and incorporates least-squares iteration to compute positions. Results are printed out in alphanumerics either on CRT or on teletype. 6502 CPU was used, although equivalent processor could be substituted (with appropriate modifications to hardware).
    Keywords: ELECTRONIC SYSTEMS
    Type: GSC-12448 , NASA Tech Briefs (ISSN 0145-319X); 5; 2; P. 151
    Format: text
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  • 5
    Publication Date: 2019-06-27
    Description: A procedure for applying covariance analysis to determine the most efficient estimation strategy for satisfying the stringent mission requirements of long arc orbit determination of applications satellites is presented. The procedure is applied to the problem of satisfying mission requirements with respect to altitude determination of GEOS-C. It is shown that requirements are met when twelve dominant geopotential coefficients are estimated along with satellite state. This application of covariance analysis is general and can be applied to future applications satellites. Recommendations for future studies are also given.
    Keywords: SPACE SCIENCES
    Type: NASA-TM-X-70610 , X-932-74-43
    Format: application/pdf
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  • 6
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    In:  Other Sources
    Publication Date: 2019-06-27
    Description: Geodetic Data Adjustment Program for reduction and error analysis of GEOS satellite data
    Keywords: COMPUTERS
    Type: COMMUN. AND SYSTEMS, INC. PROC. OF THE GEOS PROGRAM REV. MEETING, VOL. 3 FEB. 1968; P 53-58
    Format: text
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  • 7
    Publication Date: 2019-07-13
    Description: The method utilizes computer programs developed for the forthcoming ATS-F/NIMBUS-F tracking and data relay experiment where the basic tracking measurements are multiple path round-trip propagation times and rates. This method of orbit computation has recently been successfully evaluated by tracking a geostationary satellite (ATS-3) using an existing VHF (150 MHz) network of automatic transponders. A master station sequentially interrogates each transponder via the ATS-3. The master site is located at Schenectady, N. Y. and four automatic transponders were located at Shannon, Reykajavik, Buenos Aires, and Seattle respectively. Data at hourly intervals were collected during a 24 hour period on April 18-19, 1973. After correcting this data for known systematic errors it was provided as input to an orbit determination program where all satellite motions during signal propagation are rigorously accounted for. The resulting estimated ATS-3 orbit yielded observational residuals on the order of 100 meters. By using more than one satellite the present scheme is further capable of accurately locating several stationary or mobile terminals as part of the overall orbital solution.
    Keywords: COMMUNICATIONS
    Type: NASA-TM-X-70587 , X-591-74-2 , American Geophysical Union Fall Annual Meeting; Dec 10, 1973 - Dec 13, 1973; San Francisco
    Format: application/pdf
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  • 8
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    In:  Other Sources
    Publication Date: 2019-07-13
    Description: This paper describes the techniques and associated dedicated hardware utilized in locating remote beacons via satellites. Applications include those associated with a 'distress' situation or for monitoring the location of floating data collection platforms. Results obtained from experiments involving the NASA Nimbus-6 and the Amateur Satellite Corporation (AMSAT) OSCAR spacecrafts indicate position accuracies on the order of one and two kilometers are possible. The geographical location of a low power VHF transmitter is determined from Doppler data collected during a single satellite pass. A dedicated microcomputer utilizes an efficient algorithm to provide beacon position coordinates within a minute after the end of the satellite pass.
    Keywords: SPACE COMMUNICATIONS, SPACECRAFT COMMUNICATIONS, COMMAND AND TRACKING
    Type: Plenary Meeting; Jun 07, 1977 - Jun 18, 1977; Tel Aviv; Israel
    Format: text
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  • 9
    Publication Date: 2019-07-13
    Description: This paper describes the implementation of beacon location experiments involving the NASA Nimbus-6 and the Amateur Satellite Corporation (AMSAT) Oscar-6 and Oscar-7 spacecraft. The purpose of these experiments is to demonstrate the feasibility of determining the geographical location of a low power VHF 'distress beacon' via satellite. Doppler data collected during satellite passes is reduced in a mini-computer by means of a simple algorithm resulting in the simultaneous recovery of the unknown receiver coordinates and the unknown Doppler bias frequency. Results indicate point positioning to within a few kilometers - which is within the required accuracies for the positioning of downed aircraft for Search/Rescue missions.
    Keywords: AIRCRAFT COMMUNICATIONS AND NAVIGATION
    Type: Position Location and Navigation Symposium; Nov 01, 1976 - Nov 03, 1976; San Diego, CA
    Format: text
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