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Orbits and Kepler’s Laws - NASA Science Kepler's Laws
Jupiter - Wikipedia
Geostationary orbit | Satellite, Communications & Telemetry
Kepler's laws of planetary motion - Wikipedia
Venus - Wikipedia
Geocentric model | Definition, History, & Facts | Britannica
Ptolemy | Accomplishments, Biography, & Facts | Britannica
What Is an Orbit? | NASA Space Place – NASA Science for Kids
Where Does the Solar System End? | Scientific American
NASA - NSSDCA - Spacecraft - Details