Electron and Ion Spectrometer (EIS) onboard the Nozomi spacecraft

Nozomi was launched on July 4, 1998 as a Japanese first mission to the planet Mars. The main objective of this mission is to investigate the interaction between Martian atmosphere and the solar wind. The electron and ion spectrometer (EIS) is one of the fourteen instruments onboard the Nozomi spacecraft. EIS is designed to measure the fluxes of electrons, protons and heavy ions in the energy range from ∼40 keV to a few MeV. It is a compact sensor of which the weight is 1.1 kg and the size is 80×155×207 mm3 . It consists of two kinds of telescopes based on the TOF×E method (a TOF-E telescope) and on the ∼E×E method (two ∼E-E telescopes). The ∼E-E telescopes are used to measure electrons and protons, while the TOF-E telescope is mainly used to measure He, CNO-group, NeMgSi-group, and Fe-group.