Spacecraft Missions How does a scientist stuck on Earth know what the weather's like in space, or which way the solar wind is blowing? Fitted with sensors and telescopes, satellites like SOHO (Solar & Heliospheric Observatory) turn space into a vast lab, where scientists study how magnetic fields and plasmas behave. These spacecraft are Earth’s early warning system, letting us know when potentially dangerous events are taking place in space, or might soon occur. THEMIS: NASA's Time History of Events and Macroscale Interactions during Substorms (THEMIS) aims to resolve one of the oldest mysteries in space physics, to determine what physical process in near-Earth space initiates the violent eruptions of the aurora that occur during substorms in the Earth's magnetosphere. THEMIS is a 2-year mission consisting of 5 identical probes that were launched in 2007. The mission will study the violent eruptions in Earth’s magnetotail region that result in the beautiful auroras near the poles.