Space glossary

The farthest (apogee) and closest (perigee) points of an orbit around the Earth.

A maneuver that uses a planet's gravity to gain or lose speed without fuel.

A measurable clue that could reveal past or present biological activity.

A shield that absorbs the extreme heating of atmospheric reentry.

What the rocket actually carries to space: a satellite, probe, or crew.

A measure of the propulsion effort needed for a change of trajectory. The energy 'budget' of a mission.

Substances (fuel + oxidizer) burned by a rocket engine to produce thrust.

A planet orbiting a star other than the Sun.

The time slot during which a mission can lift off to reach its target.

The capacity of an environment to bring together the conditions for life: liquid water, energy, chemistry.

Region a few hundred kilometers up in altitude, where the ISS and most satellites operate.

Orbit at ≈ 36,000 km where a satellite appears fixed above a point on the equator.

The force that propels a rocket, produced by ejecting gas at high speed.

The return phase where a spacecraft passes through the atmosphere at very high speed.

A robotic vehicle designed to travel across and analyze the surface of another world.

A section of a rocket with its own engines and tanks, jettisoned once empty to lighten the launcher.