Definitions list
Click one of the letters above to advance the page to terms beginning with that letter.
  • magnetosphere
    Region around a planet where a magnetic field is the chief factor governing the behaviour of charged particles.
  • medium-Earth orbit (MEO)
    Orbit of an Earth satellite whose altitude at apogee is around 10,000 km, between low-Earth orbit and geostationary orbit.
    What is an orbit?
  • meteorite
    Fragment of an asteroid or comet, consisting of a variable-size chunk of stony or metallic matter, that can survive its passage through the atmosphere of a planet and strike the ground.
  • microgravity
    Gravity much lower than that experienced on Earth. The term zero gravity (used as a synonym for weightlessness) denotes a theoretical state that does not exist in practice. The term microgravity describes the real state of a spacecraft, which is always subjected to forces sustaining a residual gravity.
    What is weightlessness?
  • microgravité
    Gravité beaucoup plus faible que sur Terre. Ce mot est souvent employé abusivement à la place de micropesanteur, en tant que traduction maladroite du terme microgravity (en anglais, gravity signifie à la fois gravité et pesanteur)
  • microsatellite
    Satellite weighing a few tens of kilograms. Microsatellites are often designed to test technologies and auxiliary applications quickly and at low cost, alongside the main payload. Microsat in short.
  • Milky Way
    Irregular luminous band of stars and gas clouds stretching across the sky. The Milky Way is the disk of the Galaxy seen from the inside, for example from the Solar System.
  • minisatellite
    Satellite weighing a few hundred kilograms. Minisat in short.
  • Moon
    Earth’s natural satellite.
  • multiband
    Denotes a viewing instrument or mode that operates in several spectral bands at the same time. Synonym: multispectral.