The Interstellar Boundary Explorer (IBEX): Imaging the Global Heliospheric Interaction

David J. McComas

Southwest Research Institute, San Antonio, TX, USA

The Voyager spacecraft recently crossed the termination shock and is currently sending back groundbreaking observations at two locations beyond the shock, in the inner heliosheath. In contrast to essentially all prior expectations, the termination shock was not found to be the accelerator of Anomalous Cosmic Rays (ACRs), at least at the locations and times of these two crossings. Several new ideas have been suggested to explain these surprising results. Regardless of the explanation, these results highlight the limitations of local observations and importance of global observations for understanding the global processes at the termination shock and in the inner heliosheath. Fortunately, just such complementary global observations will soon be provided by the Interstellar Boundary Explorer -IBEX, which measures energetic neutral atoms (ENAs) produced via charge exchange in this region. IBEX is scheduled to launch in the fall of 2008 and will make the first global observations of the heliosphere's interaction with the interstellar medium. IBEX achieves these breakthrough observations by traveling outside of the Earth's magnetosphere in a highly elliptical orbit and taking global ENA images with two very large aperture single pixel ENA cameras. IBEX-Lo makes measurements in 8 contiguous energy pass bands covering from ~10 eV to 2 keV; IBEX-Hi similarly covers from ~300 eV to 6 keV in 6 contiguous pass bands. IBEX's high-apogee (~50 RE) orbit enables heliospheric ENA measurements by providing viewing from far outside the earth’s relatively bright magnetospheric ENA emissions. The IBEX cameras view perpendicular to the spacecraft's sun-pointed spin axis. Each six months, the spacecraft spin and progression of the sun-pointing spin axis as the Earth moves around the Sun produce energy-resolved global, all-sky images. Additional information on IBEX is available at This talk briefly summarizes the IBEX science and mission and discusses how these revolutionary observations will help inform our understanding of the global interaction between our Sun and the galaxy.