NASA's STEREO Probes Weather Temperature Extremes

The two STEREO probes leave Earth bound to take positions fore and aft of the planet in order to observe the Sun. CREDIT: NASA/JHUAPL.

A set of spacecraft twins destined to stare at the Sun is alternately baking and freezing in a preflight test.

Built to snap three-dimensional (3D) images of the Sun's most powerful eruptions for NASA's STEREO mission, the two probes are undergoing endurance checks in a vacuum chamber where temperatures can reach up to 122 Fahrenheit (50 degrees Celsius) and drop down to -13 degrees Fahrenheit (-25 degrees Celsius), NASA officials said.

"The satellites are very nearly done," Jim Adams, STEREO deputy project manager at NASA's Goddard Space Flight Center (GSFC), told reporters Monday at the 2006 meeting of American Meteorological Society in Atlanta, Georgia. "We're taking the best instruments from NASA's fleet of solar observing satellites over the years and putting them into STEREO."

Dubbed STEREO A and B by their handlers, the two spacecraft carry five telescopes each, as well as a suite of instruments to monitor the Sun for coronal mass ejections (CMEs) - massive explosions that hurl clouds of charged particles across the Solar System. The particles can interfere with the regular operations of satellites and power grids, as well as pose a danger to astronauts in Earth orbit and outside the planet's protective magnetic field.

"Because we have a flat view of the sky, we can't tell when they're coming towards us or [moving] away from us," said Alex Young, a STEREO scientist at GSFC, of CMEs. "These solar storms actually create currents that cause the magnetosphere of Earth to ring like a bell."

In 1989, a strong solar storm knocked out power in Quebec, Canada, while a severe storm slammed into the Earth in 1859, shorting out telegraph lines in the U.S. and United Kingdom and starting fires.

"It has a strong effect on our daily lives," Young said of space weather. "Today's society is extremely dependent on technology affected by them...we need to understand when these things are occurring, and when they are coming towards us."

The STEREO mission - short for Solar TErrestrial RElations Observatory - will place one satellite in an orbit ahead of Earth while its counterpart trails the planet, NASA officials said. Both satellites are designed to watch the Sun simultaneously, giving researchers a 3D view once the data is integrated on Earth, they added.

The $500 million mission is set to launch on June 24 atop a Boeing-built Delta 2 rocket, NASA officials said. Once thermal vacuum chamber tests are complete, both STEREO probes will be weighed, and then tested to ensure that their individual electronic components do not interfere with each other, they added.

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