* Astronomy

The first spacecraft designed to capture 3-D “stereo” views of the sun and solar wind were shipped, on the 9th November, from the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland., to NASA Goddard Space Flight Centre (GSFC) in Greenbelt, Maryland., for their next round of pre-launch tests.

The nearly identical twin STEREO (Solar TErrestrial RElations Observatory) observatories, designed and built by APL, were recently tested in APL’s vibration lab where engineers used a large shake table to check the structural integrity of the twin spacecraft. These tests simulate the ride into space the observatories will encounter aboard a Delta II launch vehicle from Cape Canaveral Air Force Station, Florida, where they’re scheduled for launch in spring 2006.
The launch window extends from April through June 2006 at the Cape Canaveral Air Force Station (CCAFS), Florida. Truly an international effort, its instruments were built and shipped from the United States and several European countries.

“Delivery of the twin observatories to NASA is a program milestone. Building two nearly identical spacecraft simultaneously was a technical and scheduling challenge, but one our team welcomed and tackled with extreme professionalism and dedication. With the design, construction and now delivery of the observatories to NASA Goddard, we’re very excited to help NASA get one step closer to launch and capturing the first-ever 3-D images of the sun” - Ed Reynolds, APL STEREO project manager.

During the next three months at NASA GSFC, the twin observatories will undergo additional pre-launch checks including a series of spin tests to check the spacecraft’s balance and alignment; thermal vacuum tests to duplicate the extreme temperature and airless conditions of space; and acoustic tests that simulate the noise-induced vibrations of launch. The mission team plans to transport the STEREO observatories to Florida in March 2006 for final launch preparations.
During the 2-year STEREO mission, two nearly identical space-based observatories 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 humans in space.

"STEREO is going to help us answer some of the biggest questions about the sun. Not only will we see if CMEs are moving toward Earth, but we'll see how they move through the solar system" - Dr. Michael Kaiser, Project Scientist for STEREO at the Goddard Space Flight Centre.

To obtain unique “stereo” views of the sun, the twin STEREO observatories must be placed into different orbits where they’re offset from each other and the Earth. One observatory 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.

“This is the first time lunar swingbys will be used to place multiple spacecraft into their respective orbits. Mission designers at APL will use the moon’s gravity to redirect the observatories to their appropriate orbits around the sun. This innovative mission design allows the use of a single launch vehicle” - Andy Driesman, STEREO system engineer.

After launch, the observatories will fly in an orbit from a point close to Earth to one that extends just beyond the moon. Approximately two months later, mission operations personnel at APL will synchronize spacecraft orbits, directing one observatory to its position trailing Earth in its orbit. Approximately one month later, the second observatory will be redirected to its position ahead of Earth.

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