As the solar wind from the sun flows out beyond Pluto, it collides with the material between the stars, forming a shock front. IBEX contains two neutral atom imagers designed to detect particles from the termination shock at the boundary between the Solar System and interstellar space.
"Gary Zank and his team at UC Riverside study the theory and modeling of the heliosphere and they're one of the world's best," said David McComas of the Southwest Research Institute in San Antonio, the leader of the $134-million IBEX mission, scheduled to launch in 2008.
"We're essentially providing the models and theory underpinning the mission," said Zank, who is the director of the Institute of Geophysics and Planetary Physics (IGPP) at UCR. "Over the past 10 years we've developed the models of the boundary between the solar wind with the interstellar medium." Much of the interstellar boundary is only understood as predictions based on theoretical models such as those developed by Zank.
Among the predictions IBEX is expected to confirm or refute is the existence of the hydrogen wall – a boundary comprised of piled-up hydrogen atoms and protons. IBEX will also study galactic cosmic rays, energetic particles from beyond the Solar System that pose a health and safety hazard for humans exploring beyond the earth's orbit.
IBEX will make these observations from a highly elliptical orbit that takes it beyond the interference of the Earth's magnetosphere. IBEX was selected from among 29 SMEX and eight mission-of-opportunity proposals submitted to NASA in May 2003. They were in response to an Explorer Program Announcement of Opportunity issued in February 2003. NASA selected six proposals in November 2003 for detailed feasibility studies.
"Explorer missions continue to efficiently address NASA's objectives, because of the competitive character of the Explorer Program," said Ghassem Asrar, NASA's Deputy Associate Administrator for the Science Mission Directorate.
"Dr. McComas and his co-investigators submitted a compelling proposal. It had sufficient details to convince other independent scientists, engineers, technologists, cost analysts, and program managers this is an exciting and breakthrough experiment for NASA to sponsor."
NASA's Small Explorer program (SMEX) consists of rapid, small, and focused science exploration missions.
The Explorer Program is designed to provide frequent, low-cost access to space for physics and astronomy missions with small to mid-sized spacecraft. NASA has successfully launched six SMEX missions since 1992.
Funded by NASA, for up to $450,000 each, these studies focus on cost, management, and technical plans, including small business involvement and educational outreach.
NASA's Goddard Space Flight Center in Greenbelt, Md., manages the Explorer Program for the Science Mission Directorate. Following NASA's Jan. 26 announcement of the selection of IBEX, Zank and his team at UCR began developing models of what the explorer might encounter to test the instrumentation developed by other members of the team. "This is a mission that will both validate many aspects of our models and also will tell us what areas we have to look to in future explorations," said Zank