NASA's STEREO Spacecraft Begin Sun-watching Mission
NASA's two Sun-watching STEREO spacecraft launched toward space atop a Boeing Delta 2 rocket from Cape Canaveral Air Force Station on Oct. 25, 2006.
Credit: NASA.

A pair of Sun-watching satellites launched into the night sky above Florida late Wednesday, kicking off a NASA mission to take three-dimensional (3-D) images of our nearest star.

NASA's nearly identical STEREO spacecraft rocketed spaceward atop a Boeing Delta 2 booster after a successful 8:52 p.m. EDT (0038 Oct. 26 GMT) liftoff from Cape Canaveral Air Force Station.

"The satellites are in their intended orbit and everything went as planned," NASA launch director Omar Baez said just after liftoff.

With their unique flying formation--one STEREO vehicle will eventually lead the Earth while the other lags behind--the satellites will generate the first near real-time, 3-D images of the Sun. STEREO's solar quarries are coronal mass ejections (CMEs), immense eruptions from the Sun that spew high-energy particles which can pose a radiation hazard for astronauts and satellites, as well as interfere with power and communications systems on Earth.

With NASA's plan to send astronauts on long-duration missions to the Moon--let alone a future multiple-year trip of a Mars-bound flight--more dependable CME and space weather prediction will prove vital, researchers said.

"They can receive a year's worth of radiation in one of these storms," STEREO project manager Nicholas Chrissotimos, of NASA's Goddard Space Flight Center, said of astronauts working outside a spacecraft or lunar shelter. "If we can predict when these storms occur, we can at least safe the astronauts during these timeframes so they are not exposed to this environment."

Engineers at the Johns Hopkins University's Applied Physics Laboratory built the STEREO spacecraft for NASA, and will oversee the $550 million mission from a control center in Laurel, Maryland.

Thursday's launch came after a series of delays, including last-minute range safety and booster concerns that were ultimately cleared, but only after pushing the space shot to the end of its 15-minute launch window.

"We are at the dawn of a new age of solar observation," said the U.S. Naval Research Laboratory's Russ Howard, principal investigator for one of STEREO's instrument suites. "We are going to be viewing things in a new dimension."

Eyes on the Sun

The twin STEREO--short for Solar Terrestrial Relations Observatory--spacecraft are aptly named. On vehicle, billed as Ahead, is destined to lead the Earth in its orbit while the satellite's Behind counterpart will lag aft of the planet.

In order to reach their final positions, STEREO's Ahead vehicle will slingshot around the Moon to move into an Earth-leading orbit. The Behind vehicle, meanwhile, will make another swing past the Moon to reach its Earth-trailing position. Both STEREO spacecraft are expected to slowly widen the gap between each other over time, mission managers said.

Each STEREO satellite packs 16 Sun-watching instruments into a frame about the size of a golf cart and weighs about 1,364 pounds (620 kilograms). Researchers hope to bring the Sun-watching duo online after a 90-day checkout period to add to current assets like Solar and Heliospheric Observatory (SOHO) and other missions such as Wind and Advanced Composition Explorer (ACE).

"Just like you cannot measure ocean current with just a few buoys, you really cannot try to understand this space environment with just a few observatories," NASA's STEREO program scientist Madhulika Guhathakurta said before today's launch.