NASA's Solar Terrestrial Relations Observatory (STEREO) spacecraft arrived today at Astrotech, a payload processing facility near Kennedy Space Center in Florida, to begin preparations and final testing for launch. Liftoff will occur aboard a Boeing Delta II rocket from Launch Complex 17 on Cape Canaveral Air Force Station in the summer.

STEREO consists of two spacecraft that together comprise the first mission to take measurements of the sun and solar wind in 3-D. This new view will improve our understanding of space weather and its impact on the Earth.

During its two-year mission, the two nearly identical spacecraft will explore the origin, evolution and interplanetary consequences of coronal mass ejections, the most violent explosions in our solar system. When directed at Earth, these billion-ton eruptions can disrupt satellites, radio communications and power systems. In addition, energetic particles associated with these solar eruptions are hazardous to scientific spacecraft and astronauts.

Truly an international effort, the STEREO mission utilizes scientific collaboration and instrument components provided by the United Kingdom, France, Germany, Hungary, Switzerland, and the European Space Agency. The instruments were integrated with the observatories by the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md. Spacecraft testing was performed at APL and NASA's Goddard Space Flight Center in Greenbelt, Md.

Now that both observatories are in Florida, technicians will begin the final activities to prepare them for launch. This includes integration and test activities such as: deployment of the solar arrays and high-gain antennas, installation of the flight batteries, a mission simulation for each of the two observatories (also involving the Deep Space Network), and a spacecraft Comprehensive Performance Test, an overall test of the spacecraft systems and its instruments. The observatory propulsion system will then be ready to undergo leak tests and fueling operations. Finally, the two observatories will be vertically stacked in their launch configuration for spin-balance testing before mating with the upper-stage booster. These operations are scheduled to take approximately three months.

The build-up of the Boeing Delta II rocket at Launch Complex 17 will begin later this month. The first stage is currently planned to be erected on Pad 17-B during the last week of May, followed by the attachment of the nine solid rocket boosters. The second stage is currently planned to be hoisted atop the first stage late in the first week of June.

STEREO is targeted for transportation to the launch pad and mating with the Delta II on July 10. The initial launch period for STEREO extends from July 22 to Aug. 6.