Low energy ion mass spectrometer for the EXOS-D satellite

Satellite observations have revealed that accelerated ionospheric ions flow out into the magnetosphere. A new instrument, which combines the functions of the retarding potential analyzer and the Bennett mass spectrometer and can analyze these accelerated ions, has been developed and launched on the scientific satellite, EXOS-D known as AKEBONO after launch. It is highly sensitive in the low-energy range. This paper describes the operating principles and characteristics of this instrument, and discusses performance before the flight and on the orbit.