Friday, March 14, 2008

GeoEye 1 - How It Works


Popular Science has an excellent animated article on the features of GeoEye 1. GeoEye 1 should be in orbit later this year.

How It Works: The Best View From Space Yet | Popular Science

Here are some of the features about this system:

  • First non-military satellite that uses military grade GPS.
  • Has a star-tracker system - that is used in addition to the GPS units to determine its position more accurately. This translates to 1.5 times higher accuracy in determining the position of a pixel on the ground.
    The star-tracker system observes stars and uses them to determine the satellites position in relation to our planet.
    Any object on the planet's surface can be mapped to within 3 meters of its actual location.
  • When the satellite is over a location where it needs to start performing a capture - it turns the "Reaction wheels". This puts a spin on the satellite and help orient the satellite so as to be pointing correctly to take its image. (The reaction wheels spin in reverse to bring the satellite to a halt!)
  • The satellite scans in strips. The strips are 37,500 pixels long (1 pixel wide). The camera can capture 20,000 such strips in 2 seconds.
  • Each pixel can have a resolution of up to 16 inches on the ground - black and white. In color the resolution drops down to 5.5 feet.
    • The high resolution imagery is available only to the US government (and possibly countries that the US designates as ok to receive this higher resolution imagery).
    • All other countries will get data that has been re-sampled down to 20 inch resolution.
  • The satellite can capture approximately 270,000 sq. miles of data per day (700,000 sq. kms)
  • GeoEye will be able to sell the data commercially around the world (probably not to restricted countries like Iran).
  • GeoEye 1's primary customer is the US National Geospatial Agency (NGA).
  • The satellite has a planned life of seven years.
  • The satellite will be in polar orbit. Will have the ability to revisit any location approximately every 3 days.


1 meter resolution


0.41 meter resolution (16 inches) - simulated.

More information is available at

Also check out their gallery of satellite images:

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