Stereo Spacecraft Make First 3d Images Of Sun

“The improvement with STEREO's 3D view is like going from a regular X-ray to a 3D CAT scan in the medical field,” said Dr. Michael Kaiser, STEREO Project Scientist at NASA's Goddard Space Flight Center in Greenbelt, Md.

NASA's STEREO (Solar Terrestrial Relations Observatory) spacecraft were launched on October 25, 2006, and on January 21 completed a series of complex manoeuvres, including flying by the moon, to position the spacecraft in their mission orbits. The two observatories are orbiting the sun, one slightly ahead of Earth and one slightly behind, separating from each other by approximately 45 degrees per year. Just as the slight offset between your eyes provides you with depth perception, this separation of the spacecraft allows them to take 3-D images and particle measurements of the sun.

Violent solar weather originates in the sun's atmosphere, or corona, and can disrupt satellites, radio communication, and power grids on Earth. The corona is translucent, like a ghost in an old movie, and it flows along the sun's tangled magnetic fields, so it sometimes looks like spaghetti gone wild. It's hard for scientists to tell which structures are in front and which are behind.

Images from the SECCHI (Sun Earth Connection Coronal and Heliospheric Investigation) telescopes on each spacecraft are being combined to create the 3D views. The detectors for all the STEREO cameras were built at the Science and Technology Facilities Council’s Rutherford Appleton Laboratory in the UK. The HI cameras on SECCHI were built at the University of Birmingham.

Professor Richard Harrison of the Rutherford Appleton Laboratory (RAL) said “Understanding the complex processes that happen in our Sun is a big challenge. Using the two eyes of our STEREO spacecraft we are able to see in 3 dimensions, allowing us to understand the relative positions of matter around the Sun and measure more precisely where the front of a CME is.”

Dr Chris Davis, also from RAL said “It is a tribute to UK engineering that these wonderful 3D images are only possible because of the detector systems developed at the Science Technology Facilities Council.”

Andy Breen of the University of Wales Aberystwyth added “We've always known that we need to study the Sun in three dimensions in order to understand the complex structures in the solar atmosphere. STEREO provides us with the first opportunity to do this. University of Wales Aberystwyth have been involved in STEREO planning from an early stage and, with the help of See3D, we are now in a terrific position to be one of the first to exploit these data”

See3D are a 3D visualisation company recently spun-out from the University of Wales, Aberystwyth. They have developed 3D projection facilities which will provide UK scientists with unprecedented views of the complex 3D structure of the Sun and its extended atmosphere.

STEREO's depth perception will also help improve space weather forecasts. Of particular concern is a destructive type of solar eruption called a Coronal Mass Ejection, or CME. CMEs are eruptions of electrically charged gas, called plasma, from the sun's atmosphere. A CME cloud can contain billions of tons of plasma and move at a million miles per hour. The CME cloud is laced with magnetic fields, and CMEs directed our way smash into Earth's magnetic field. If the CME magnetic fields have the proper orientation, they dump energy and particles into Earth's magnetic field, causing magnetic storms that can overload power line equipment and radiation storms that disrupt satellites.

Satellite and utility operators can take precautions to minimize CME damage, but they need an accurate forecast of when the CME will arrive. To do this, forecasters need to know the location of the front of the CME cloud. STEREO will allow scientists to accurately locate the CME cloud front.

Dr Chris Eyles of the University of Birmingham said “STEREO will allow scientists to study the 3D structure of a CME cloud and predict in advance which ones will cause serious magnetic storms with the potential to cause problems on Earth.”

The first 3D images from STEREO are being provided by NASA's Jet Propulsion Laboratory in Pasadena, California. STEREO is the third mission in NASA’s Solar Terrestrial Probes program. STEREO is sponsored by NASA’s Science Mission Directorate, Washington, D.C. The Goddard Science and Exploration Directorate manages the mission, instruments, and science centre. The Johns Hopkins University Applied Physics Laboratory, Laurel, Md., designed and built the spacecraft and is operating them for NASA during the mission. The STEREO instruments were designed and built by scientific institutions in the US, UK, France, Germany, Belgium, Netherlands, and Switzerland.

UK scientists and engineers have contributed to STEREO by building the HI (Heliospheric Imager) cameras for the SECCHI package on each observatory. HI is a wide angled imaging system (meaning it has a broad field of view) and will be studying how CMEs propagate, particularly those that are likely to affect the Earth. HI was funded by the Science and Technology Facilities Council. The Council’s Rutherford Appleton Laboratory is responsible for the scientific exploitation of the heliospheric imagers as well as providing the detectors used in all of STEREO's camera systems. Both heliospheric imagers were built in the UK at the University of Birmingham.

The University of Wales Aberystwyth is one of the first UK institutions to work on exploiting the data and producing 3D simulations via their spin-out company See3D.