Spacecraft Designed to Capture 3-D Views of Sun Set For Launch

Built and operated for NASA by the Johns Hopkins University Applied Physics Laboratory (APL), in Laurel, Md., the two-year STEREO (Solar TErrestrial RElations Observatory) mission will explore the origin, evolution and interplanetary consequences of coronal mass ejections. These powerful solar eruptions are a major source of the magnetic disruptions on Earth and a key component of space weather, which can greatly affect satellite operations, communications, power systems, and the lives of astronauts in space.

“Building and testing two spacecraft simultaneously has been a technical and scheduling challenge, but an effort at which we’ve been successful,” says Ed Reynolds, APL STEREO project manager. “The entire STEREO team is so proud and excited to launch the twin observatories and be part of the first mission to capture coronal mass ejections in 3-D.”

To capture the sun in 3-D, the twin observatories will fly as mirror images of each other. One of the observatories will be placed ahead of Earth in its orbit around the sun and the other behind. Just as the slight offset between your eyes provides you with depth perception, this placement will allow the STEREO observatories to obtain 3-D images and particle measurements of the sun.

Placing STEREO into Orbit
STEREO mission designers determined that the most efficient and cost-effective way to get the observatories into space was to launch them aboard a single rocket and use lunar swingbys to place them into their respective orbits. This is the first time lunar swingbys have been used to manipulate orbits of more than one spacecraft. Mission designers will use the moon’s gravity to redirect the observatories to their appropriate orbits – something the launch vehicle alone can’t do.

After launch the observatories will initially fly in an elliptical orbit that extends from Earth just beyond the moon. Approximately two months later, mission operations personnel at APL will synchronize spacecraft orbits and direct one observatory to its position trailing Earth. Approximately three months after launch, the second observatory will be redirected to its position ahead of Earth.

Each STEREO observatory will carry two instruments and two instrument suites, providing more than a dozen instruments per observatory. APL designed and built the spacecraft platform housing the instruments. When combined with data from observatories on the ground or in space, STEREO’s data will allow scientists to track the buildup and liftoff of magnetic energy from the sun and the trajectory of Earth-bound coronal mass ejections in 3-D.

STEREO’s instruments were built by numerous organizations worldwide with a principal investigator, or PI, leading each instrument team. The instruments and PIs are as follows: Sun-Earth Connection Coronal and Heliospheric Investigation (SECCHI) – Russell Howard, Naval Research Laboratory; In situ Measurements of PArticles and CME Transients (IMPACT) – Janet Luhmann, University of California, Berkeley; PLAsma and SupraThermal Ion Composition (PLASTIC) – Antoinette Galvin, University of New Hampshire; and STEREO/WAVES (S/WAVES) – Jean-Louis Bougeret, Paris Observatory, Meudon.

STEREO is the third mission in NASA’s Solar Terrestrial Probes Program. STEREO is sponsored by NASA’s Science Mission Directorate, Washington, D.C. NASA Goddard’s Solar Terrestrial Probes Program Office, in Greenbelt, Md., manages the mission, instruments and science center. APL designed and built the STEREO spacecraft and will operate the twin observatories for NASA during the mission.

For more information about STEREO or to download additional images, visit http://stereo.jhuapl.edu.