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HST Pointing Control System Diagram

HST Pointing Control System Diagram

Hubble uses some very basic physics to turn itself around and look at different parts of the sky. Located on the telescope are six gyroscopes (which, like a compass, always point in the same direction) and four free-spinning steering devices called reaction wheels.

The gyroscopes sense when the telescope needs to be repointed. When they "tell" Hubble that it needs to turn itself, a computer gives a command to give the reaction wheels a "push" or "spin."

  • Release Date
    August 31, 2005
  • Science Release
    Hubble Space Telescope Begins “Two-Gyro” Science Operations
    Read the release
  • Credit
    Illustration: NASA, ESA, A. Feild and K. Cordes (STScI), and Lockheed Martin

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Hubble Space Telescope Rate Gyro Assemblies

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Hubble has a sophisticated system that controls its position 24 hours a day. It is called the Pointing Control System (PCS). The PCS is composed of gyroscopes, reaction wheels, and fine guidance sensors.

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Last Updated
Mar 28, 2025
Contact
Media

Claire Andreoli
NASA’s Goddard Space Flight Center
Greenbelt, Maryland
claire.andreoli@nasa.gov

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