June 23, 2013
NASA Marks Fifth Anniversary Of TWINS Mission
redOrbit Staff & Wire Reports - Your Universe Online
This month marks the fifth anniversary of NASA’s Two Wide-angle Imaging Neutral-atom Spectrometers (TWINS) missions, which are stereoscopically imaging the mysterious and dynamic region surrounding Earth known as the magnetosphere, the US space agency announced on Saturday.The TWINS A & B probes were launched on June 15, 2008, and according to NASA, since that time they have been orbiting in widely separated planes so that they can enable the three-dimensional visualization and the resolution of large scale structures and dynamics within the magnetosphere for the first time.
The magnetosphere itself is “governed by magnetic and electric forces, incoming energy and material from the sun, and a vast zoo of waves and processes unlike what is normally experienced in Earth-bound physics,” the agency explained in a statement. “Nestled inside this constantly changing magnetic bubble lies a donut of charged particles generally aligned with Earth’s equator.”
That region is known as the ring current, and NASA said its waxing and waning is a key part of the space weather that surrounds the Earth. The ring current can induce magnetic fluctuations on the ground as well as transmit disruptive surface charges onto spacecraft, and part of the TWINS mission has been to provide the first and currently only stereo view of this portion of the magnetosphere.
During its five years of operation, the TWINS satellites have successfully provided 3D images and global characterization of this region, NASA said. The probes have been tracking how the magnetosphere responds to space weather storms.
They have also been able to characterize global information such as the temperature and the shape of various structures within this outer layer of the ionosphere, and have helped enhance magnetosphere models which can be used to create simulations of a plethora of different events.
“With two satellites, with two sets of simultaneous images we can see things that are entirely new,” said Mei-Ching Fok, the project scientist for TWINS at NASA’s Goddard Space Flight Center. “This is the first ever stereoscopic energetic neutral atom mission, and it’s changed the way we understand the ring current.”
“We’ve done some fantastic new research in the last five years,” added David McComas, the principal investigator for TWINS at the Southwest Research Institute in San Antonio, Texas. “As a mission of opportunity, it is a very inexpensive mission and it continues to return incredible science.”
The two TWINS satellites travel in what is known as a Molniya orbit – a highly elliptical orbit during which they spend the bulk of their time approximately 20,000 miles above the Earth’s surface. Their mission was only originally scheduled to last two years, but the project was officially extended for three more years in 2010. According to NASA, a second multi-year extension is currently pending.
“TWINS science is based on two instruments that can track neutral atoms,” the agency explained. “The first is a neutral atom imager that records the atoms that naturally stream away when a neutral atom collides with an ion. This allows the instrument to map the original ions from far away – as if it could see atoms the way we see light – instead of only collecting data from the areas of space it passes through.
“The other instrument on TWINS is a Lyman alpha detector, which can measure the density of hydrogen from afar, and in this case observes the hydrogen cloud around Earth, the geocorona,” they added. “Most importantly, these instruments exist on both of the TWINS spacecraft. Much of the successful research in the last five years relies on the ability to watch these neutrals from two viewpoints, allowing scientists to analyze not only speed and number of particles, but also to determine the angles at which the particles left their original collisions.”
Thanks to the satellite’s stereo vision, scientists have been able to gather in-depth information regarding how the magnetosphere reacts to space storms, no matter if they were created due to the impact of a coronal mass ejection or if they result from a solar wind twist known as a co-rotating interaction region.
Furthermore, TWINS has revealed that the pitch angle at which ions travel around Earth is different on each side of the planet – a discovery that can help researchers discover whether they are more likely to escape from the ring current out into space or to ultimately funnel down toward Earth.
“TWINS is a stereo mission, providing the first observations of the neutral atoms from two vantage points, but two spacecraft give us another advantage/ Two spacecraft provide continuous coverage of the ring current, as one set of instruments always has a view,” said Goddard magnetospheric scientist Natalia Buzulukova.