(satellite observing the ISM/heliosphere boundary)
The Interstellar Boundary Explorer (IBEX)
is a NASASmall Explorer Program (SMEX)
space mission dedicated to mapping the
boundary between the solar system and interstellar space.
It was launched in 2008 with the goal of a 2-year
mission but remains active in 2026 and has the potential
to operate for about thirty more years.
Its work is detecting energetic neutral atoms (ENAs, which are generally
from the heliosheath),
carrying out this work from Earth orbit.
The instruments are IBEX-Hi and IBEX-Low
which detect higher and lower energy ENAs.
The IBEX ribbon is a narrow ring-shaped region of the
celestial sphere from which more than the usual number of ENAs
arrive. It is of research interest, but generally presumed to be
an effect of the galactic magnetic field surrounding the
solar system.