 NASA's  Interstellar Boundary Explorer (IBEX) to map the boundary between the solar system and interstellar space will be launched on a Pegasus XL rocket today. The two year mission, costing US$165 million, will study the region in space where the solar wind from the sun suddenly slows down as it reaches the thin, cold gas of interstellar space.  This region, called the  heliospheric boundary of the solar system, helps to deflect most of the potentially life-threatening forms of radiation coming from elsewhere in our galaxy.
IBEX will ride Pegasus to around 200 kilometres from earth, before boosting itself into its final earth orbit 322,000 kilometres away. The probe will capture energetic neutral atoms (ENAs), which are formed when positive ions in the solar wind hit neutral atoms of interstellar material and rip out electrons from them. IBEX-Lo and -Hi detectors will collect data on the ENAs to create a three-dimensional map of the heliosphere.
The heliospheric boundary was first probed by  Voyager 1 in 2004 and later by  Voyager 2 in 2007. The data from the two missions indicated several indentations on the heliospheric boundary. It is hoped that IBEX studies may reveal the cause of these indentations. 
Recent observations indicate the solar wind pressure has weakened by 25 percent over the past decade and is presently at its weakest level in 50 years. Ibex studies could help confirm whether and why the heliosphere is shrinking. Scientists postulate that if the heliosphere continues to weaken, the amount of cosmic radiation reaching the inner parts of our solar system, including earth will increase. This could trigger growing levels of disruption to electrical equipment, damage satellites and possibly harm life on earth.
"Around 90 per cent of the galactic cosmic radiation is deflected by our heliosphere, so the boundary protects us from this harsh galactic environment," said Nathan Schwadron, co-investigator on the IBEX mission at  Boston University. "IBEX gives us a chance to look at how our Solar System's bubble fits in as a tiny piece of the entire Galaxy," claimed David McComas of the  Southwest Research Institute in  San Antonio, Texas, and IBEX's principal investigator.

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NASA mission to map the boundary of solar system