Possible effects on avionics induced by terrestrial gamma-ray flashes

Abstract. Terrestrial gamma-ray flashes (TGFs) are impulsive (intrinsically sub-millisecond) events associated with lightning in powerful thunderstorms. TGFs turn out to be very powerful natural accelerators known to accelerate particles and generate radiation up to hundreds of MeV energies. The number ratio of TGFs over normal lightning has been measured in tropical regions to be near 10−4. We address in this Article the issue of the possible susceptibility of typical aircraft electronics exposed to TGF particle, gamma ray and neutron irradiation. We consider possible scenarios regarding the intensity, the duration, and geometry of TGFs influencing nearby aircraft, and study their effects on electronic equipment. We calculate, for different assumptions, the total dose and the dose-rate, and estimate single-event-effects. We find that in addition to the electromagnetic component (electrons/positrons, gamma rays) also secondary neutrons produced by gamma-ray photo production in the aircraft structure substantially contribute to single-event effects in critical semiconductors components. Depending on the physical characteristics and geometry, TGFs may deliver a large flux of neutrons within a few milliseconds in an aircraft. This flux is calculated to be orders of magnitude larger than the natural cosmic-ray background, and may constitute a serious hazard to aircraft electronic equipment. We present a series of numerical simulations supporting our conclusions. Our results suggest the necessity of dedicated measurement campaigns addressing the radiative and particle environment of aircraft near or within thunderstorms

High resolution imaging of the sodium and potassium exosphere from Mercury Planetary Orbiter

International audienc

Preliminary optical design of the stereo channel of the imaging system simbiosys for the BepiColombo ESA mission

The paper describes the optical design and performance budget of a novel catadioptric instrument chosen as baseline for the Stereo Channel (STC) of the imaging system SIMBIOSYS for the BepiColombo ESA mission to Mercury. The main scientific objective is the 3D global mapping of the entire surface of Mercury with a scale factor of 50 m per pixel at periherm in four different spectral bands. The system consists of two twin cameras looking at \ub120\ub0 from nadir and sharing some components, such as the relay element in front of the detector and the detector itself. The field of view of each channel is 4\ub0 x 4\ub0 with a scale factor of 23\u2019\u2019/pixel. The system guarantees good optical performance with Ensquared Energy of the order of 80% in one pixel. For the straylight suppression, an intermediate field stop is foreseen, which gives the possibility to design an efficient baffling system

High resolution imaging of the sodium and potassium exosphere from Mercury Planetary Orbiter

International audienc

High resolution imaging of the sodium and potassium exosphere from Mercury Planetary Orbiter

International audienc

A novel optical design for the stereo channel of the imaging system SIMBIOSYS for the BepiColombo ESA mission

In this paper the design of a novel catadioptric optical solution for the Stereo Channel (STC) of the imaging system SIMBIOSYS for the BepiColombo ESA mission to Mercury is presented. The main scientific objective is the 3D global mapping of the entire surface of Mercury with a scale factor of 50 m per pixel at periherm in five different spectral bands. The system consists of two sub-channels looking at \ub120\ub0 from nadir. They share the detector and all the optical components with the exception of the first element, a rhomboid prism. The field of view of each channel is 5.3\ub0 \ub4 4.5\ub0 and the scale factor is 23 arcsec/pixel. The system guarantees an aberration balancing over all the field of view and wavelength range with optimal optical performance. For stray-light suppression, an efficient baffling system able to well decouple the optical paths of the two subchannels has been designed

Method for studying the effects of thermal deformations on optical systems for space application

In this paper, the results of the thermo-elastic analysis performed on the stereo channel of the imaging system Integrated Observatory System for the BepiColombo European Space Agency mission to Mercury are presented. The aim of the work is to determine the effects of ambient parameter variations on the equipment performance; the optical performance is changing during the mission lifetime primarily because of the optics misalignments and deformations induced by temperature variations. The camera optics and their mountings are modeled and processed by a thermo-mechanical finite element model (FEM) program, which reproduces the expected optics and structure thermo-elastic deformations in the instrument foreseen operative temperature range, i.e., between 1220 \ub0C and 30 \ub0C. The FEM outputs are elaborated using a MATLAB optimization routine: an algorithm based on nonlinear least square data fitting is adopted to determine the surface equation (plane, spherical, nth polynomial) which best fits the deformed optical surfaces. The obtained surfaces are then directly imported into a ZEMAX code for sequential ray-tracing analysis. Variations of the optical spot diagrams, modulation transfer function curves, and ensquared energy are then computed. The overall analysis shows that the preferred solution for mounting the optical elements is adopting the kinematic constraints instead of using the classical glue solution