Cassini as a heliospheric probe - the potential of pick-up ion measurements during its cruise phase

Measurements of the spatial distributions of pick-up ions can be utilized t o infer important information about the structure of the heliosphere. First , a determination of the symmetry axis of flux distributions of pick-up ion s not experiencing any significant filtration of their neutral parent atoms in the heliospheric interface represents a new method to derive the orient ation of the upwind-downwind axis of the heliosphere from observation. Seco nd, a comparison of pick-up ion flux distributions resulting from neutrals both filtered and not filtered during their passage through the heliospheri c interface might provide insight into the geometry of the interface and, s ub-sequently, give information about the strength and orientation of the lo cal interstellar magnetic field. A feasibility study for carrying out such measurements with the Cassini spacecraft is presented, and the most promisi ng pick-up ion candidates are identified. (C) 1998 Elsevier Science Ltd. Al l rights reserved.