What is perigee?
Also called: lowest point of an orbit
Perigee is the point in an orbit where a spacecraft is closest to Earth. It is where the spacecraft is moving fastest, and where the thin upper atmosphere drags on it most.
Perigee and apogee are a pair: the near point and the far point of the same oval. A perfectly circular orbit has neither, which is why the space station — whose orbit is very nearly circular — is usually quoted as a single altitude instead.
Perigee matters because it decides how long an orbit lasts. Even at hundreds of kilometres up, there is enough gas to cause drag, and a low perigee dips the spacecraft into thicker air on every lap.
That drag is why the station needs regular reboosts. Left alone, it would slowly spiral down and reenter.
See it happen
Space & OrbitsFalling foreverSource: International Space Station