THEMIS Celebrates Five Years of Watching Aurora and Space Weather

Aurora and Space Weather

People still talk about the launch. 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. A critical sequencing guided how each spacecraft launched into space, first the top one, then the ones on the outside, so the platform would remain balanced and stable.

"The launch of THEMIS was one of the first Explorer missions I oversaw from concept through launch and on-orbit checkout and it still stands out in my mind," says Willis Jenkins, the Program Executive for NASA's Explorers Program, a program that supports less expensive and highly focused missions. "Trying to get five spacecraft together on one rocket was a challenge, but our team came up with unique ways to build and launch them."

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.

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