Cosmic Radiation Effects on Avionics, an Increasing Hazard in the New Millennium?

With the increasing use of microelectronics of ever diminishing feature size, systems are becoming increasingly susceptible to single event effects arising from the highly ionising interactions of cosmic rays and solar particles. Such single event effects include soft errors, involving both single and multiple bits, and hard errors due to latch-up or burn-out. For space systems an increasing body of evidence has accumulated over the last twenty years, systems have been lost and expensive ground control procedures have had to be invoked. Although cosmic-ray effects are now a normal part of the specification, expensive mistakes are still made. While the earth’s atmosphere shields out most of the primary cosmic rays, there is a build up of secondary neutrons which reach a maximum at around 60000 feet and are only a factor of three diminished at 30000 feet. By sea level there is a further factor 300 diminution. As a result of this mechanism the radiation hazard at aircraft altitudes is as severe as in certain low-earth orbits. During the past ten years there has been increasing evidence of single event effects on aircraft electronics as well as in sealevel systems. At the same time there is new legislation on the allied problem of the effects of these neutrons on aircrew and frequent flyers. The problem is expected to increase as more low power, small feature size electronics are deployed in More Electric aircraft. In addition, the current period of solar maximum activity following the turn of the millennium is likely to provide large solar particle events which can penetrate to aircraft altitudes. A Cosmic Radiation Effects Working Group has been established to pool research information on this problem. The work programme is described together with some initial results.