Names like the Hubble Space Telescope and the International Space Station frequently make headline news for their groundbreaking achievements. Such stardom, however, would be difficult without the crucial support of NASA’s lesser known Tracking and Data Relay Satellites, or TDRS. The eight satellites that currently compose the fleet provide continuous connectivity for sending navigation, data and voice transmissions from Earth to the space station, Hubble and a host of other spacecraft. Without them, communications with ground stations would be limited to just 15 percent of the time. Watch the video to learn more.