The in - Orbit Radiation Environment and Its Effects on Space - Borneinstrumentationp

An overview is given on the various components of the radiation environment of the ISO mission, including cosmic rays, geomagnetically trapped protons and electrons, and the solar proton events. Various aspects related to the radiation shielding and to the radiation-induced eeects on instrumentation will also be discussed. For the beneet of future missions, relevant lessons learned concerning ISO radiation environment and its eeects will nally be sum-marised. 1. INTRODUCTION The ISO mission was operational between November 1995 and May 1998. Although this was nominally in the solar minimum period, two moderate solar proton events occurred towards the end of mission, the rst a double-event in November 1997 and the second, shorter one in April 1998. The eeects of the rst event were clearly registered by all four of the ISO instruments, while the second one, already in the decommissioning phase of the mission, had measurable eeects on the ISO star tracker. Apart from these events, the ISO observations were continuously aaected by the steady cosmic ray bombardment in the science windows, as well as by the energetic electron uxes in the Earth's radiation belts. The detector "background" resulting from these particles and/or from their secondaries formed the bulk of the glitches analysed by the four instrument teams. In Section 2 of this presentation, an overview is given on the various contributors of the ISO radiation environment. The role of spacecraft and instrument shielding in modifying the incident radiation is discussed in Section 3, while Section 4 lists some of the most prominent radiation eeects on space instrumentation. Discussion on ISO lessons learned and the relevance for a number of future infrared missions are nally included in Sections 5 and 6.