Solar Spacecraft Celebrate Six Years In Service
October 29, 2012

Milestone Marks Sixth Anniversary Of NASA STEREO Spacecraft

redOrbit Staff & Wire Reports - Your Universe Online

On Thursday, October 25, NASA's twin Solar Terrestrial Relations Observatory (STEREO) program celebrated its sixth anniversary orbiting the sun, the US space agency announced on Friday.

The twin orbiting probes were launched on that date in 2006, and ultimately entered into similar but separate orbits around the sun. STEREO-A's orbit is slightly smaller and faster, while STEREO-B's is larger and slower, they said, and those subtle differences have helped the vehicles achieve some interesting milestones.

"As one spacecraft gained an increasing lead over Earth, the other trailed further and further behind," NASA officials said. "In February of 2011, each STEREO spacecraft was situated on opposite sides of the sun, and on Sept. 1, 2012, the two spacecraft and the Solar Dynamics Observatory (at Earth) formed an equal-sided triangle, with each observatory providing overlapping views of the entire sun."

"By providing such unique viewpoints, STEREO has offered scientists the ability to see all sides of the sun simultaneously for the first time in history, augmented with a view from Earth's perspective by NASA's Solar Dynamics Observatory (SDO)," they added.

Not only does that allow scientists to view of all of the sun's active regions before they rise over the horizon, but combining the two views is "crucial for three-dimensional observations of the giant filaments that dance off the sun's surface or the massive eruptions of solar material known as coronal mass ejections (CMEs)," NASA explained.

STEREO is the third mission in the American space agency's Solar Terrestrial Probes program (STP). It is scheduled to be a two-year mission, and provided the first-ever stereoscopic measurements to study the relationship between the Earth and the sun, as well as the nature of CMEs. The project is headed up by NASA's Goddard Space Flight Center, which is located in Greenbelt, Maryland.

On August 13, NASA revealed that one of the STEREO spacecraft had observed what might have been the fastest CME ever detected on the sun. Researchers at Goddard recorded that giant cloud traveling at speeds of 1,800 to 2,200 miles per second as it departed from the sun, making it at least "one of the top five CMEs ever measured by any spacecraft," according to solar scientist Alex Young.