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The two major factors contributing to the opposition brightening of Saturn'srings are i) the intrinsic brightening of particles due to coherentbackscattering and/or shadow-hiding on their surfaces, and ii) the reducedinterparticle shadowing. We utilize the Hubble Space Telescope observations fordifferent elevation angles B to disentangle these contributions. We assume thatthe intrinsic contribution is independent of B, so that any B dependence of thephase curves is due to interparticle shadowing, which must also act similarlyfor all colors. We construct a grid of dynamical/photometric simulation modelsto fit the elevation-dependent part of opposition brightening. Eliminating themodeled interparticle component yields the intrinsic contribution to theopposition effect: for the B and A rings it is almost entirely due to coherentbackscattering; for the C ring, an intraparticle shadow hiding contribution mayalso be present.  Based on our simulations, the width of the interparticle shadowing effect isroughly proportional to B. This follows from the observation that as Bdecreases, the scattering is primarily from the rarefied low filling factorupper ring layers, whereas at larger $B$'s the dense inner parts are visible.The elevation angle dependence of interparticle shadowing also explains most ofthe B ring tilt effect (the increase of brightness with elevation). Fromcomparison of the magnitude of the tilt effect at different filters, we showthat multiple scattering can account for at most a 10% brightness increase as B-> 26^o, whereas the remaining 20% brightening is due to a variable degree ofinterparticle shadowing. The negative tilt effect of the middle A ring is wellexplained by the the same self-gravity wake models that account for theobserved A ring azimuthal brightness asymmetry.

The opposition and tilt effects of Saturn's rings from HST observations