CU Selected To Build $2.5 Million Worth Of Electronics For Satellites To Analyze Earth Space Storms

April 21, 2003

Two University of Colorado at Boulder faculty members have been selected to design and build $2.5 million worth of electronics for a fleet of five satellites to study violent magnetic activity around Earth that triggers auroral storms at the poles.

The five NASA satellites will orbit from 30,000 miles to 120,000 miles above Earth's surface as part of the Time History and Events and Macroscale Interactions during Substorms project, or THEMIS. THEMIS will study magnetic "substorms" caused by rapid changes in the magnetic field in space that can produce some of the brightest and most active northern and southern lights seen from Earth.

Associate Professor Robert Ergun of CU-Boulder's astrophysical and planetary sciences department, or APS, and Xinlin (pronounced Shinlyn) Li, an associate professor in the aerospace engineering sciences department, are co-investigators on the project. Both Li and Ergun are research scientists at CU-Boulder's Laboratory for Atmospheric and Space Physics.

The bright aurora borealis in the northern hemisphere and the aurora australis in the southern hemisphere are generated as electrons rain down along magnetic field lines onto the poles, triggering colorful light shows. 

"During a magnetic substorm, the Earth's magnetic fields change violently," said Ergun. "Substorms occur on a daily basis and can combine to create major magnetic storms. We want to understand magnetic storms and substorms not only because they affect the environment in space, but also to understand the behavior of magnetic fields in astrophysical objects."

"The advantage of having five spacecraft orbiting at different altitudes should allow us to better understand the process by which the auroras are created and to determine the source of so-called 'killer electrons,' " Li said. "It is not yet clear how these very energetic electrons are accelerated in space."

Severe solar storms have been blamed for disabling satellites and knocking out huge power grids in the northeast United States and Canada in recent years. "These particles can penetrate spacecraft and the spacesuits of astronauts. They have the potential to be very dangerous," said Li.

"This is the first NASA constellation mission to study the magnetosphere of Earth," he said. "It gives us an advantage to have five identical spacecraft to study the cause of the auroras each night. To predict space weather we need to understand the origin of these electrons that light up the auroras."

Ergun called it a "technological first" in launching a synchronized series of satellites to pinpoint events in Earth's magnetic field. "The digital signal processors we are building will be the 'smarts' that will help determine the origin of these electron storms," he said.

The digital signal processors will weigh only 1-2 pounds, said Li.

"We expect CU-Boulder postdoctoral, graduate and undergraduate students to help analyze the information and model it to determine the formation and depletion of the radiation belt around Earth in the coming years," said Ergun.

THEMIS is part of NASA's Medium Class Explorer program. Slated for launch in 2007, the $173 million mission involves several universities and is being led by the University at California, Berkeley.

Additional information and artist's concepts of THEMIS are available on the Web at

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