TERMIUM Plus®

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horizon sensor [1 record]

Record 1 2007-02-05

English

Subject field(s)
  • Spacecraft
  • Applications of Electronics
  • Aircraft Piloting and Navigation
DEF

A radiometer or other sensor that is used to align or control the axis of a spacecraft, missile, or satellite with the apparent horizon of the Earth or of any other astronomical body.

CONT

Horizon sensors [are] the primary means for directly determining the attitude of a spacecraft relative to the Earth ... The attitude of spacecraft relative to Earth is one of the most important aspects of attitude determination and control, particularly for communications (TDRSS), weather (GOES), Earth resources (LANDSAT), satellites, etc. Earth cannot be treated as a point source like the Sun, especially for near Earth satellites for which Earth covers about 40% of the sky. Therefore, merely detecting the Earth is by no means sufficient for attitude determination, even for the most crude attitude determination requirements. Hence most sensors are designed to detect the Earth's horizon. Horizon sensors are infrared devices that detect the contrast of the cold of space and the warmth of the Earth (or other body).

CONT

Typically there are four basic components in a horizon sensor: a scanning mechanism, optical system, radiance detector, and signal processing electronics.

OBS

horizon sensor: term officially approved by the RADARSAT-2 Terminology Approval Group (RTAG).

Key term(s)
  • infra red horizon sensor

French

Domaine(s)
  • Engins spatiaux
  • Applications de l'électronique
  • Pilotage et navigation aérienne
DEF

Scanneur mécanique à détecteurs électro-optiques montés de façon à repérer l'horizon terrestre.

CONT

Garde-cap. Il s'agit d'un gyroscope que l'on maintient horizontal et qui définit une direction fixe dans le plan horizontal à sa dérive près. Le gyroscope est monté à la Cardan comme dans le cas du compas mais il n'est pas balourdé. Un détecteur d'horizon monté sur la caisse de tore délivre un signal proportionnel à l'inclinaison du moment cinétique; ce signal est traité et est envoyé dans un moteur couple d'axe ce qui crée un couple vertical ramenant le moment cinétique horizontal.

CONT

[...] un système de contrôle d'attitude et d'orbite qui comprend : [...] un capteur optique 2-axes qui peut détecter soit la Terre (typiquement capteur d'horizon Infra-Rouge) soit l'Étoile Polaire (typiquement capteur à matrice CCD).

OBS

capteur d'horizon : terme uniformisé par le Groupe de travail de la terminologie de RADARSAT-2 (GTTR).

Spanish

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