  The scientific apparatus "Gamma-400" designed for study of hadron and
electromagnetic components of cosmic rays will be launched to an elliptic orbit
with the apogee of about 300 000 km and the perigee of about 500 km. Such a
configuration of the orbit allows it to cross periodically the radiation belt
and the outer part of magnetosphere. We discuss the possibility to use hybrid
pixel detecters based on the Timepix chip and semiconductive sensors on board
the "Gamma-400" apparatus. Due to high granularity of the sensor (pixel size is
55 $mu$m) and possibility to measure independently an energy deposition in each
pixel, such compact and lightweight detector could be a unique instrument for
study of spatial, energy and time structure of electron and proton components
of the radiation belt.
