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The newspaper of The Johns Hopkins University October 30, 2006 | Vol. 36 No. 9
Twin APL-Built, Solar-Studying Spacecraft Successfully Launched

By Kristi Marren
Applied Physics Laboratory

NASA's STEREO spacecraft — en route as the first mission to capture the sun in 3-D — successfully launched on Oct. 25 aboard a single Delta II vehicle from Cape Canaveral Air Force Station, Fla., at 8:52 p.m.

The two nearly identical spacecraft, designed, built and operated by the Johns Hopkins Applied Physics Laboratory for NASA, separated from the launch vehicle 25 minutes after liftoff. After receiving the first signal from the spacecraft 63 minutes after launch, mission control personnel at APL confirmed each observatory's solar arrays successfully deployed and were providing power to the spacecraft. The initial radio signals were forwarded to the APL-based mission operations center from NASA's Deep Space Network antennas in Canberra, Australia.

During its two-year mission, the twin observatories (named STEREO for Solar TErrestrial RElations Observatory) 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.

For the next few weeks, the spacecraft will fly in an elliptical orbit that extends from Earth to just beyond the moon. During this time, mission operations personnel at APL will place the spacecraft in flight mode, turn on and check out all instruments and subsystems, and ensure all systems are operating nominally in preparation to begin their data collection efforts.

In approximately two months, the APL team will synchronize spacecraft orbits and direct one observatory to its position ahead of Earth; about a month later, it will redirect the second observatory to its position trailing Earth. Just as the slight offset between your eyes provides you with depth perception, this placement will allow the observatories to obtain 3-D images and particle measurements of the sun.

Lunar swingbys will take advantage of the moon's gravity to redirect the observatories to their appropriate orbits, something the launch vehicle alone can't do. This is the first time lunar swingbys have been used to manipulate orbits of more than one spacecraft.

Each observatory is carrying 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.


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