Cosmic-ray flux detected by an IR bolometer operated on board of a stratospheric aircraft

A bolometer was flown as an infrared detector on a stratospheric aircraft at altitudes of approximately 19 km during the APE campaign, which took place in Rovaniemi (Finland) in the period December 1996–January 1997. The signal impulses produced in the bolometer by the thermalisation of the ionisation induced by cosmic charged particles in the sensitive layer of the detector have been analysed. A statistics of approximately 4000 cosmic-ray events was recorded during four flights. In the period of the observations the solar activity was near its minimum. The observations from a stratospheric aircraft has made possible the collection of a first sampling of cosmic-ray flux variation with latitude and altitude. A comparison is made with previous balloon observations at the same altitudes. Model calculations are compared to the observed cosmic-ray energy loss distribution in the bolometer. The results are useful for the understanding of cosmic-ray background effects occurring in applications of high sensitivity bolometers in aircraft-borne measurements.