As advancements in exploration allowed spacecraft to travel farther and observe other worlds more closely, it became apparent that some of these sophisticated instruments could be used to see Earth as it had never been seen before. With that goal in mind, the Seasat satellite launched in 1978 to test four Earth-observing radar instruments. The pioneering mission collected more ocean topography data than the previous 100 years worth of shipboard data and laid the groundwork for future missions.

With a series of radar-imaging missions flying aboard the Space Shuttle starting in the 1980s, and a new suite of imaging instruments aboard NASA's Terra satellite in the late 1990s, most of Earth has been mapped and can be seen in greater detail than ever before.
Seeing Earth from space gives insight into environmental changes, weather patterns, and natural hazards like earthquakes and volcanoes.

Of particular importance in understanding Earth is the interaction between the oceans, covering 70 percent of our planet, and the atmosphere. The Topex/Poseidon satellite, managed jointly by NASA and the French Space Agency, launched in 1992 to study global ocean circulation and climate interactions between the seas and atmosphere. Its follow-on mission, Jason 1, launched in 2001 to join Topex/Poseidon in Earth orbit and continue the ocean monitoring.

In 2002, the innovative Gravity Recovery and Climate Experiment mission launched to precisely measure Earth's shifting water masses and map their effects on Earth's gravity field. This mission consists of two spacecraft flying in tandem. One day, scientists hope to fly spacecraft in deep space in tandem so they can study the distant stars.

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