Landsat 4

NASA launches Landsat 4, the fourth Landsat Earth resource observation satellite and the first to be redesigned from the ground up (previous Landsats had been based on NASA’s Nimbus satellites from the 1960s and ’70s). For the first time, Landsat data processing and distribution is handled by another government agency, the U.S. Geological Survey, which partners with NASA on all future Landsat satellites. Landsat 4 is the first Landsat to link up to NASA’s TDRS (Tracking & Data Relay Satellite) system, thus enabling real-time data transmission to Earth even when Landsat 4 isn’t passing over a ground station. Landsat 4 remains operational through the end of 1993.