Twin spacecraft blasted off Wednesday night on a mission to study huge eruptions from the sun that can damage satellites, disrupt electrical and communications systems on Earth and endanger spacewalking astronauts.
The lift off was delayed by several minutes after launch managers became concerned late in the countdown that winds could blow toxic material over nearby Port Canaveral should there be an accidental explosion.
However, the area was cleared of people, mainly government workers, permitting the rocket to soar off the launch pad with a roar.
Flight controllers cheered, applauded and gave each other handshakes after the spacecraft separated from the rocket less than a half hour after launch.
Scientists hope the $550 million, two-year mission will help them understand why these eruptions occur, how they form and what path they take.
The eruptions — called solar flares — typically blow a billion tons of the sun's atmosphere into space at a speed of 1 million mph. The phenomenon is responsible for the Northern Lights, or aurora borealis, the luminous display of lights seen in the upper latitudes of the Northern Hemisphere.
"Of the bazillion stars that we have in our night sky, the sun is the only one that counts," said NASA scientist Madhulika Guhathakurta. "Any understanding or breakthrough we can make in understanding the sun and the sun's environment is of direct relevance to every human being on this planet."
The two observatories will provide scientists with the first-ever three-dimensional view of the sun by working in tandem, like a set of eyes, in different orbits.
NASA hopes information about the solar flares helps the astronauts who fly to moon and eventually Mars in the coming decades. Astronauts exposed to the eruptions can receive a year's worth of radiation.
The spacecraft's launch was delayed several times this year because of technical problems.
Scientists plan to release to the public movies and other images created by the STEREO spacecraft, though viewers may need to use the type of 3-D glasses worn for movies like "Creature From the Black Lagoon."