Modeling Performance of Ultra-Sensitive In-Orbit Infrared Telescopes

This paper evaluates considerations in minimizing disruptions of scientific data in ultra-sensitive Infrared (IR) spaced-based telescopes by charged particles in space radiation. The particles modeled are protons, alphas, and heaver ions with an atomic number as high as that of iron. Performance results of proposed designs are based on a model developed at Boeing. The components modeled are the spectra of the ion species in cosmic rays and solar flares, the transport of the primary ions and secondary particles produced including neutrons, the generation electron hole pairs (EHPs) by the particles penetrating the focal point array (FPA), and a component modeling transfer of EHPs from generation to recombination. Results indicate noise levels above 100 EHPs by secondary particles alone per pixel in in intense space weather events; these observations agree with empirical data sources. Space based IR astronomical observatories now have a noise level of 100 electrons/pixel indicating the need of detailed radiation transport models; in near future designs where the pixel pitch reduces from 25 to 5 microns, the radiation model component becomes even more significant. Measures reducing the number of electrons per pixel below the threshold are discussed. .