Twin spacecraft blasted off 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 two spacecraft, known as STEREO, for Solar Terrestrial Relations Observatory, lifted off on Wednesday night, stacked one on top of the other, aboard a single Delta II rocket.
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 30 minutes after launch.
Scientists hope the US$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 tonnes of the sun's atmosphere into space at a speed of 1.6 million kph. 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," NASA scientist Madhulika Guhathakurta said. "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 will help the astronauts who fly to the 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.