Coordinates and Satellite Orbits
Coordinates and Satellite Orbits
Coordinates and Satellite Orbits
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2013/3/6Latitude <strong>and</strong> LongitudeJyh-Ching Juang, EE, NCKUA position on the surface of the Earth is expressed in terms oflatitude <strong>and</strong> longitude.Latitude is expressed as being either north or south of theequatorLongitude as either east or west of the prime meridian.Longitude <strong>and</strong> latitude are measured in terms ofdegree:minute:second North polePi Prime meridianTo vernal equinox equator3Jyh-Ching Juang, EE, NCKUEarth Coordinate SystemsEarth-Centered Inertial (ECI) coordinate system.Origin: geocenterx-axis: points toward vernal equinoxz-axis: aligns with the Earth’s spinaxisy-axis: completes a right-h<strong>and</strong>ed systemEarth-Centered Earth-Fixed (ECEF) coordinate system.Origin: geocenterz-axis: along the polar axisx-axis: through the Greenwich meridiany-axis: through 90-deg east longitudeRelationship between ECI <strong>and</strong> ECEF systemsThe ECI coordinate system is related to the ECEF coordinate systemby the Earth rate <strong>and</strong> the time of the year.[ e ] [ i ]r R ( 3 ) r42
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