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 a t altitudes of approximately 19 km during the APE campaign, which took plac e in Rovaniemi (Finland) in the period December 1996-January 1997. The sign al impulses produced in the bolometer by the thermalisation of the ionisati on induced by cosmic charged particles in the sensitive layer of the detect or have been analysed. A statistics of approximately 4000 cosmic-ray events was recorded during four flights. In the period of the observations the so lar activity was near its minimum. The observations from a stratospheric ai rcraft has made possible the collection of a first sampling of cosmic-ray f lux variation with latitude and altitude. A comparison is made with previou s balloon observations at the same altitudes. Model calculations are compar ed to the observed cosmic-ray energy loss distribution in the bolometer. Th e results are useful for the understanding of cosmic-ray background effects occurring in applications of high sensitivity bolometers in aircraft-borne measurements. (C) 1999 Elsevier Science B.V. All rights reserved.