Meet the satellites that relay data from space to the ground.
With two-thirds of our planet covered in water, satellites observing Earth in low orbit or in elliptical orbits aren't always in range of stations on the ground that can receive their data. That's where NASA's network of Tracking and Data Relay Satellites, or TDRS, comes in. These ten satellites circle Earth out in geosynchronous orbit, turning with Earth to remain in position over the same spot on the ground. From this position, one of these communications satellites is always within range of the science satellites - and the ground stations on Earth that can receive their data. Managed by NASA's Goddard Space Flight Center, TDRS satellites relay science data and spacecraft operating data back to Earth, as well as track the spacecraft's location. They also relay commands from engineers on the ground to the satellites. Watch the videos to learn more.