(a) The ICARE_NG² flight model for HB13F with the sensors on the left of the instrument and the electronic box on the right. (b) Electron response function of the PE2 detection head aboard HB13F in anticoincidence mode. The inserted image corresponds to cross-sections of the response function, showing geometric factors as a function of incident energy. These geometric factors correspond to those actually used for count-flux conversions, as described in the next section.