Space rendezvous

Space rendezvous is the maneuvering of two spacecraft into the same orbit and relative position so they can meet, approach, or dock.

Orbital mechanics: The study of how objects move under gravity, including spacecraft in orbit. Rendezvous requires changing orbital paths and timing so both spacecraft reach the same place together.
Gemini 6A: The 1965 crewed spaceflight that achieved the first rendezvous between two crewed spacecraft. Its meeting with Gemini 7 demonstrated that crews could coordinate orbital rendezvous.
Kepler's laws of planetary motion: Three laws describing the motion of bodies in elliptical orbits around a central mass. They explain why spacecraft in different orbits move at different speeds and return to positions predictably.
Space interception: A maneuver in which a spacecraft reaches another object or trajectory, without necessarily matching its orbit or stopping nearby. Interception aims to cross a target's path; rendezvous matches its orbit and relative position.
Hohmann transfer orbit: An elliptical orbit used to transfer between two circular orbits in the same plane with two engine burns. A transfer orbit can change a chaser's orbital altitude before it matches a target's orbit.
Gemini 7: A NASA crewed mission launched in 1965 that served as the target for Gemini 6A's rendezvous. It was the passive spacecraft in the first rendezvous between crewed vehicles.
Orbital period: The time an orbiting object takes to complete one revolution around its primary body. A small difference in orbital period changes how quickly two spacecraft gain or lose orbital position.
Space docking: The controlled physical connection of two spacecraft in orbit. Docking is one possible conclusion of rendezvous, not a synonym for the entire maneuver.
Phasing orbit: An orbit chosen to change a spacecraft's position relative to another spacecraft over time. A chaser can use a phasing orbit to gain or lose orbital angle before rendezvous.
Apollo 9: The 1969 crewed mission that tested the Apollo lunar module and command module in Earth orbit. Its spacecraft practiced rendezvous and docking techniques needed for lunar missions.

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