Aqua (EOS PM-1) is a multi-national NASA scientific research satellite in orbit around the Earth, studying the precipitation, evaporation, and cycling of water. It is the second major component of the Earth Observing System (EOS) preceded by Terra (launched 1999) and followed by Aura (launched 2004).
The name "Aqua" comes from the Latin word for water. The satellite was launched from Vandenberg Air Force Base on May 4, 2002, aboard a Delta II rocket. Aqua is on a Sun-synchronous orbit. It flies leading the satellite formation called the "A Train" with several other satellites (Aura, CALIPSO, CloudSat and the French PARASOL).
Aqua carries six instruments for studies of water on the Earth's surface and in the atmosphere: