"We are at the dawning of a new age of solar observations," Russ Howard of the Naval Research Laboratory said at a NASA news conference.
The two-year Solar Terrestrial Relations Observatory (STEREO) mission will be the first to view the sun from two separate vantage points outside Earth's orbit.
The nearly identical twin spacecraft will act like a pair of human eyes, each picking up data that is correlated, with data from observatories on the ground and in low-Earth orbit, into a third-dimension vision of the Sun and its influences.
"We're going to be viewing things in a new dimension for us," Mr Howard said.
Mr Howard said STEREO also was unique because it will see "broadside" the entire relationship between the sun and Earth, some 150 million kilometres apart.
And, he said, "for the first time we will be able to measure optically what the other instruments on STEREO ... are seeing in their instruments."
Scientists hope the mission will glean insight into solar activities such as coronal mass ejections (CMEs), the most violent explosions in our solar system.
When aimed at Earth, these billion-tonne eruptions of the sun's corona spew intense radiation, severely disrupting the Earth's environment and endangering astronauts and scientific spacecraft.
Information gleaned on the origins and behaviours of CMEs would allow more accurate forecasting, which would improve planning for space missions as well as over-the-pole flights, satellite communications and video transmissions.
NASA has devised a unique launch of the two solar-powered observatories, using the moon's gravity like a pinball flipper to send them into opposite and slightly distinct orbits around the sun.
At first they will be placed in a highly eccentric Earth orbit, the National Aeronautics and Space Administration explained, then after a few weeks, the two spacecraft -- named "A", for "Advance", and "B", for "Behind" -- are expected to drift slowly apart but stay relatively close to each other as they line up for their close encounter with the moon about one month into the mission.
"This is when the relatively small distance between the two spacecraft makes all the difference," the space agency said on its website.
The "Behind" spacecraft will be flung completely away from Earth, and will become a satellite of the sun, while the "Ahead" spacecraft will curve back to fly past the moon a second time six weeks later, and be flung out in the opposite direction.
The total cost of the international mission is US$550 million, the STEREO project manager, Ed Reynolds of Johns Hopkins University Applied Physics Laboratory said.
The STEREO solar observatories are scheduled to launch tomorrow aboard a Boeing rocket from Cape Canaveral Air Force Station in Florida.