scholarly journals A Laser Polar Motion Experiment

1972 ◽  
Vol 48 ◽  
pp. 121-122
Author(s):  
David E. Smith ◽  
Peter J. Dunn ◽  
Ronald Kolenkiewicz
Keyword(s):  
Space Flight ◽  
New York State ◽  
Earth Tides ◽  
Systematic Change ◽  
Orbital Inclination ◽  
Laser Tracking ◽  
Goddard Space ◽  
Chord Distance ◽  
Goddard Space Flight Center

SummaryFor three months in 1970, NASA, Goddard Space Flight Center conducted an experiment to try and detect the motion of the Earth's pole of rotation by laser ranging to an Earth satellite. Two laser tracking stations were used, one at Goddard Space Flight Center and one near Seneca in New York State, 408 km away and on the same meridian as the Goddard station. The objective of the experiment was to precisely measure the orbital inclination of the Beacon Explore C spacecraft, on a daily basis and with a resolution of a few hours, to a few hundredths of an arc second by the simultaneous tracking of the spacecraft as it passed between the two stations. During the experiment over fifty thousand range measurements on over two hundred revolutions of the satellite were obtained and on fifty occasions the satellite was simultaneously tracked at both stations. The noise accuracy of the tracking varied between 20 and 60 cm during most of the experiment and the orbital inclination obtained from the measurements showed a systematic change of about 25 arc sec, due primarily (about 80%) to the gravitational perturbation of the orbit by the Sun and the Moon. Perturbations by solar radiation pressure and the solid-Earth tides appear to account for most of the remaining systematic changes in the inclination and from which it has been possible to derive a value of Love's number for the Earth as A preliminary determination of the motion of the pole in the meridian containing the stations by subtracting the known perturbations (including tides) from the observed perturbation suggests that an accuracy of 3 to 5 m has been obtained, over periods of about 6 hr, during the latter part of the experiment. The experiment has also demonstrated that the present laser tracking systems are able to measure the chord distance between the two tracking stations with a repeatability of 25 to 30 cm.The present analysis of the data is directed towards an improved extraction of the gravitational perturbations and an improved determination of the Love number k2.A full account of the experiment and its results so far will be published elsewhere.

A Study of the Geoid in Canada

1974 ◽  
Vol 28 (3) ◽  
pp. 259-272
Author(s):  
Gérard Lachapelle
Keyword(s):  
New Brunswick ◽  
Satellite Data ◽  
Space Flight ◽  
Goddard Space ◽  
Goddard Space Flight Center ◽  
Map Service

An astrogeodetic determination of the geoid in certain parts of Canada was made with data available at the end of 1970. The astrogeodetic leveling method was used. The western and eastern parts of Canada were adjusted independently owing to the lack of data in the Province of Ontario. Five satellite stations located across Canada were chosen as initial points of the astrogeodetic geoid. Comparisons with two other astrogeodetic geoids — U.S. Army Map Service 1967 and University of New Brunswick 1973 — and one geoid obtained from a combination of gravimetric and satellite data— Goddard Space Flight Center 1972 — were made. A relative agreement of about five metres was found in every case for most parts covered by the present astrogeodetic geoid except in Newfoundland and Yukon.

scholarly journals Compendium of Single Event Effect Results from NASA Goddard Space Flight Center

2016 ◽  
Author(s):  
Martha V. O'Bryan ◽  
Kenneth A. LaBel ◽  
Carl M. Szabo ◽  
Dakai Chen ◽  
Michael J. Campola ◽  
...  
Keyword(s):  
Space Flight ◽  
Single Event ◽  
Nasa Goddard Space ◽  
Single Event Effect ◽  
Goddard Space ◽  
Goddard Space Flight Center

A discussion on orbital analysis - Radio tracking at Winkfield

1967 ◽  
Vol 262 (1124) ◽  
pp. 46-49
Keyword(s):  
Space Flight ◽  
Joint Venture ◽  
Radio Telemetry ◽  
Research Station ◽  
Radio Tracking ◽  
Goddard Space Flight Center ◽  
Telemetry Measurements ◽  
Orbital Analysis ◽  
The U.S

Winkfield is one of the stations in the Space Tracking and Data Acquisition Network (Stadan) of the U.S. National Aeronautics and Space Administration (N.A.S.A.) and is operated by the Radio and Space Research Station as a joint venture with N.A.S.A. The stations in the network, using standardized equipment supplied by N.A.S.A., receive by radio telemetry measurements from the various experiments in the satellites, they command the functioning of satellites and they track them. Tracking, with which this paper is concerned, means the measurement of quantities which contribute to the determination of the positions of satellites as a function of time. About ten stations in the network use tracking equipment and methods identical with those used at Winkfield. The network operates 24 h a day, its functioning being coordinated by the Goddard Space Flight Center of N.A.S.A. by means of teleprinter circuits which also serve to convey the raw tracking information from the stations to the N.A.S.A. computer facilities.

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