Definitions list
Click one of the letters above to advance the page to terms beginning with that letter.
  • panchromatic
    Describes a viewing instrument or mode that is sensitive to all colours across the visible spectrum.
  • parabolic flight
    Trajectory flown by an aircraft to create conditions of weightlessness for a few seconds.
  • passivation
    Set of techniques applied to spacecraft to avoid generating unwanted orbital debris. In particular, passivation involves averting the risks of residual propellants exploding in the upper stages of launch vehicles.
  • payload
    1. Cargo (satellite, orbital station element, probe, capsule) carried and orbited by a launch vehicle

    2. Instruments specific to a satellite’s or probe’s mission, as opposed to the bus on which they are mounted.
    A payload may be a satellite carried by a launch vehicle, or an experiment payload on the satellite itself.
  • periapsis
    Point on a satellite’s orbit nearest the centre of the body around which it gravitates. For example, when Earth is the centre of attraction, the term perigee is used; if the Moon, perilune; if Jupiter, perijove; and if the Sun, perihelion.
  • perigee
    Point on a satellite’s orbit nearest the centre of the Earth.
  • perturbed orbit
    Trajectory that deviates slightly from a Keplerian orbit due to uneven distribution of mass within the two bodies, to forces other than mutual attraction or to collisions with other particles in their vicinity.
    What is an orbit?
  • pesanteur
    Sensation de lourdeur éprouvée à la surface d’un astre très massif, comme la Terre ou la Lune. C’est aussi la force attractive exercée par un astre sur un corps posé à sa surface ou présent dans son atmosphère. Elle inclut la gravité de cet astre et l’effet de sa rotation sur lui-même.
    Qu'est-ce que l'impesanteur ?
  • Photovoltaic
    Term describing solar panels or solar cells which directly convert light into electricity.
  • pitch
    Motion of a body around its pitch axis, usually perpendicular to the roll axis. The pitch axis may be perpendicular to a spacecraft’s plane of symmetry or to the plane of its trajectory.
  • planet
    Celestial body that does not emit its own light and orbits the Sun or another star.
  • planetology
    Science dedicated to studying the physical properties of planets and their natural satellites.
  • plasma
    Gas whose atoms are completely ionized and therefore consists of ions, electrons and atomic nuclei. It is estimated that 99% of matter in the Universe is in the form of plasma.
  • plate-forme bus
    Plate-forme standard utilisable pour des missions différentes.
  • polar
    Describes a satellite or the orbit of a satellite that passes over the Earth’s poles.
    What is an orbit?
  • polar orbit
  • polarimeter
    Instrument designed to measure rotation of the plane of polarization of light when it passes through certain substances.
  • polarization
    Property of certain electromagnetic waves, especially light waves, in which vibrations may be oriented in one or more particular directions.
  • precession
    Slow, natural shifting of the plane of an orbit over time. For example, precession of the Earth is due to flattening at the poles and its equatorial “bulge” (the radius at the equator is 20 km larger than at the poles).
  • pressurize
    To produce and maintain a set pressure inside a chamber, for example, inside the flight deck of a spacecraft.
  • Prime contractor
    Organization with contractual responsibility for managing all activities that contribute to the execution of a product. The prime contractor is ultimately responsible for quality, schedules and prices.
  • propellant
    Oxidizer or fuel used by a rocket engine.
  • propergol
    Produit composé d’un ou plusieurs ergols capables, par réaction chimique, de fournir l’énergie de propulsion d’un moteur-fusée.
  • Prophylactorium
    Building at Star City where cosmonauts are quarantined before and after a spaceflight.
  • propulsion
    Production of a force to propel a spacecraft.