IBEX uses two sensors to collect energetic neutral atoms (ENAs) coming from the boundary of the Solar System. These ENAs are made from the interaction between solar wind particles and atoms from the interstellar medium. Solar wind particles are usually charged, meaning they have lost electrons. Another name for a particle that has lost one or more electrons is an “ion”. Sometimes these solar wind ions interact with neutral atoms that come from the interstellar medium (ISM). Neutral atoms contain equal numbers of protons and electrons. The solar wind ions take electrons from these neutral ISM atoms and get deflected from their original path. Since the solar wind particles are now neutral, they no longer react to magnetic fields in the area. They travel very quickly in a straight line from the spot where the interaction occurred.
Some of the ENAs happen to get knocked in a straight line in just the right way so that they travel in through the Solar System toward the IBEX spacecraft. To make sure that only ENAs enter IBEX's collectors, stray ions are deflected before they even enter the collectors. The sensors, called IBEX-Hi and IBEX-Lo, sort the particles and keep track of the direction of travel of all of the particles, the time they entered the sensor, the mass of the particles, and the amount of energy each particle has. This information is sent to Earth via the antenna aboard IBEX, and the IBEX team uses all of this information to make maps of the Solar System boundary.