THEMIS Celebrates Its Five Years in Space

It was the first and so far, only time NASA has launched five satellites at one time.

Carefully balanced inside a Delta II rocket, the five THEMIS (short for Timed History of Events and Macroscale Interactions during Substorms) spacecraft were launched into space from Cape Canaveral at 6:01 p.m. ET on February 17, 2007. The spacecraft were nestled in a ring shape, four around the outside and one on a middle pedestal. Those five satellites working in tandem was crucial for THEMIS job of tracking energy as it moves through space. Energy and radiation from the sun impacts and changes Earth’s magnetic environment, the magnetosphere, and such impacts cause “space weather” that can harm satellites in space. As they orbit around Earth, the THEMIS satellites work together to gather data on how any given space weather event travels through space – something impossible to understand with a single spacecraft, which cannot differentiate between an occurrence that happens throughout space, rather than in a single location. Since 2007, the THEMIS satellites have reinvigorated studies of the magnetosphere, mapping the details of how explosive auroras occur, how the solar wind transfers energy to Earth’s space environment, and how chirping waves in space relate to blinking auroras on Earth. During its prime, two-year mission, THEMIS main objective was to pinpoint where a space weather phenomenon known as substorms originate. Substorms generate aurora, but before THEMIS launched no one knew exactly what created the onset of a substorm. Using its five satellites, as well as an array of some 25 ground based instruments, the THEMIS team could watch how the substorms formed and how they correlated to events in the night sky. Together, the instruments painted a complete picture of aurora formation. In the second half of 2012, NASA will launch two new spacecraft, the Radiation Belt Storm Probes (RBSP) that will specifically be studying this region and how the belts swell and shrink in response to outside effects. In 2014, NASA will launch four spacecraft called the Magnetospheric Multiscale mission (MMS) that will study the physics of magnetic reconnection at the boundaries of the magnetosphere. The orbit for THEMIS lies in between the orbits for RBSP and MMS. THEMIS has the potential to unify observations from these missions into a nine-satellite global constellation to observe the entire course of energy release from the entire length of its travels from the edges of the magnetosphere to impact with the near-Earth space that is crowded with satellites vulnerable to incoming space weather.