Follow this link to skip to the main content NASA Jet Propulsion Laboratory California Institute of Technology JPL HOME EARTH SOLAR SYSTEM STARS & GALAXIES SCIENCE & TECHNOLOGY BRING THE UNIVERSE TO YOU JPL Email News RSS Podcast Video
JPL Banner
Ocean Surface Topography from Space
EDUCATION
T/P's "Triple Tracking"
TOPEX/Poseidon Measurement System



  • A ground-based beacon called "DORIS" sends radio signals to a satellite receiver that measures the "Doppler." The "Doppler effect" is what causes the distinctive sound pattern you hear when a car passes. The distance between your ear and the car changes as it passes and so does the frequency of the sound waves generated by the car;
  • Light from ground-based lasers is reflected off mirrors on the T/P satellite; and
  • The Global Positioning System (GPS) network is used. At times, a T/P receiver tracks several GPS satellites simultaneously and, because the position of GPS satellites is well-known, T/P's position can be calculated. This was originally only an experiment but is now a very reliable data source.

Link to USA.gov
Site Manager: Margaret Srinivasan
Webmaster: Kristy Kawasaki
JPL Clearance: CL01-1707