The Aurora project: Estimation of the optical sail parameters

The thrust model for computing a sailcraft trajectory contains thermo-optic al parameters that are averages over the spectrum of the incident photons, namely, with respect to energy, intensity and polarization. These parameter s are not observables and could change considerably from a sail to sail for a number of practical reasons. The mission analysis for a sailcraft is a p rogressive task from a simple trajectory propagator to the orbit determinat ion. Aurora sailcraft mission analysis has advanced another step forward by processing experimental data related to aluminium. Once appropriate fittin g functions have been selected, differential specular and diffused reflecta nce and differential absorptance have been averaged over incident solar spe ctrum, assumed a Planckian here. The result has been to get incident-angle- dependent optical parameters more reliable than mere literature values. The procedure has entailed the computation of grids of complicated definite in tegrals. They are particularly important during the trajectory optimization of the Aurora solar flyby, a very sensitive profile that would allow the s ailcraft to achieve cruise speeds ranging from 12 to 20 AU/yr. (C) 1999 Els evier Science Ltd. All rights reserved.