Washington, October 2006
NASA's twin Solar Terrestrial Relations Observatories (STEREO) mission, two nearly identical golf-cart-sized spacecraft, launched October 25 from Cape Canaveral in Florida.
STEREO observations will help researchers build the first-ever three-dimensional views of the sun. The images will show the star's stormy environment and its effects on the inner solar system -- vital data for understanding how the sun creates space weather.
The mission includes significant international cooperation with European partners in instrument development, data sharing and analysis, according to an October 25 NASA press release.
"The stunning solar views the two observatories will send back to Earth," said Nick Chrissotimos, STEREO project manager at NASA's Goddard Space Flight Center in Maryland, "will help scientists get a better understanding of the sun and its activity than we've ever been able to obtain from the ground or any of our other missions."
The two observatories, launched on a Delta II rocket in a stacked configuration, separated from the launch vehicle 25 minutes after liftoff.
After receiving the first signal from the spacecraft 63 minutes after launch, mission control personnel confirmed each observatory's solar arrays successfully deployed and were providing power. NASA's Deep Space Network antennas in Canberra, Australia, received the initial radio signals.
During the next two weeks, mission managers at the Johns Hopkins University Applied Physics Laboratory in Maryland will make sure all systems are working properly.
In the next three months, the observatories will fly from a point close to Earth to one just beyond the moon's orbit. After about two months, STEREO's orbits will be synchronized to encounter the moon.
The "A" observatory will use the moon's gravity to redirect it to an orbit "ahead" of Earth. The "B" observatory will encounter the moon again for a second swing-by about a month later to redirect its position "behind" Earth. Ahead and behind refer to the satellites' positions relative to Earth in orbit around sun.
Each observatory has 16 instruments, including imaging telescopes and equipment to measure solar wind particles and to perform radio astronomy.
STEREO is the first NASA mission to use separate lunar swing-bys to put two observatories into much different orbits around the sun.
Just as the slight offset between human eyes produces depth perception, this placement will allow the STEREO observatories to obtain three-dimensional images of the sun. The arrangement also allows the spacecraft to take local particle and magnetic field measurements of the solar wind as it flows by.
During the observatories' two-year mission, they will explore the origin, evolution and interplanetary consequences of coronal mass ejections, some of the most violent explosions in our solar system.
These billion-ton eruptions can produce spectacular aurora and disrupt satellites, radio communications and Earth's power systems. Energetic particles associated with the solar eruptions permeate the entire solar system and can be hazardous to spacecraft and astronauts.
Better prediction of solar eruptions gives more warning time for satellite and power-grid operators to put their systems into a safe mode to weather the storm. A better understanding of the nature of these events will help engineers build better, more resilient systems.
"We're becoming more and more reliant on space technologies in our everyday lives and are hatching ambitious plans to explore our outer space surroundings," said Michael Kaiser, STEREO project scientist at Goddard.
"But nature has a mind of its own," he added, "and STEREO is going to help us figure out how to avoid those surprises the sun tends to throw at us and our best-laid plans."