STEREO launches towards the Sun

STEREO (Solar TErrestrial RElations Observatory) comprises two nearly identical observatories that will orbit the Sun to monitor its violent outbursts known as coronal mass ejections (CME’s). These powerful solar eruptions are a major component of “space weather” which can impact Earth, satellites and astronauts.

The spacecraft launched at 8.52 pm EDT (1.52 am in the UK) on a Delta II rocket, with the two observatories being stacked one on top of the other. They separated from the launch vehicle approximately 25 minutes after lift off. Some 63 minutes later mission control received the first signals from the spacecraft which indicated that each observatory’s solar arrays had successfully deployed and were providing power.

Speaking live from the launch site Dr Chris Davis from CCLRC Rutherford Appleton Laboratory, one of members of the UK STEREO team said, “The launch was truly spectacular with the spacecraft blazing through the dark night sky and providing an amazing reflection in the Banana River. This year’s fireworks displays will be a real let down in comparison!”

Professor Keith Mason, CEO of the Particle Physics and Astronomy Research Council (PPARC) said, “We look forward with great anticipation to seeing the results from these twin observatories. Such in depth observations of the sun will provide invaluable information that will affect future activities in space and on Earth building on the success of previous missions such as YOHKOH and SOHO, and the recently launched Solar-B mission.”

The twin observatories will fly as mirror images of each other to obtain unique “stereo” views of the sun’s activities. One observatory will be placed ahead of Earth in its orbit around the sun and the other behind. Such positioning will allow the STEREO observatories to obtain 3-D images and sample the wind of the particles flying out from the Sun.

Lunar swingbys will be used to place the observatories into their correct orbits. This is the first time that lunar swingbys have been used to manipulate orbits of more than one spacecraft.

For the first couple of months the observatories will fly in an orbit from a point close to Earth to one that extends beyond the moon. Then mission operations personnel will synchronise 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. STEREO will then operate for a further two years.

UK scientists from CCLRC Rutherford Appleton Laboratory and the University of Birmingham built and will operate one of the instruments on each of the spacecraft.