Adv. SpaceRes. Vol. 17, No. 3, pp. (3)99-(3)102. zyxwvutsrqponmlkjih lY96 copyngllt 0 1995 COSPAR 0273- 1177(95)00505-6 Printed in Great Britain. All ri hts nscrvd 0273-I 177196 b.50 + 0.06 DUST STUDIES ON A SOLAR PROBE I. Mann* and E. Griin** * zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Max-Plunck-InstitutjiIr Aeronomie, Postfach 20. D-37189 Katlenburg-Lb&u, Germuny ** Max-Planck-lnstitutfr Ketvphysik, Postfach 10 39 80, D-69029 Heidelberg, Germany ABSTRACT This paper discusses the dust distribution in the solar vicinity and relevant effects to be considered when planning a solar probe. We can characterize four different components of the dust cloud and their orbital parameters. For the planning of a solar probe payload we discuss goals of zyxwvutsrqponmlkjih a dust experiment and the different possibilities for impact detectors in comparison to remote sensing experiments. INTRODUCTION The existence of dust in the solar vicinity is obvious from the brightness of the F-corona, which, according to recent model calculations (/l/, /2/), is mainly produced by these particles. Knowledge about the dust could be achieved with a dedicated solar probe experiment but also knowledge about this dust complex is needed in advance in order to protect a solar probe from high velocity dust impacts (/3/). micrometeoroids originating from comets and asteroids, or even from interstellar space, as shown most recently by dust measurements onboard ULYSSES (/4/), approach the sun on a time scale of lo4 to lo5 years due to the deceleration caused by the Poynting-Robertson effect. Different effects such as radiation pressure, corpuscular pressure, magnetic forces (/5/) and erosion processes are expected to become particularly important in the inner solar system. This leads to complex dynamics before particles sublimate completely or again leave the solar system in unbound orbits (see /G/). F rom this we expect a dust free zone around the sun which however, from the most recent eclipse data (/7/, /8/), could not be identified within the region of distances greater than 3 solar radii around the sun (/9/). Although the sublimation of near solar dust is negligible in connection with the dynamics of the solar wind, on the other hand, it nevertheless could possibly influence the solar wind composition (see /lo/). The present knowledge and understanding of dust particles is gathered from Zodiacal light and F-corona observations (VIS and IR), in-situ impact measurements and laboratory analysis of collected particles. The description of the circum-solar- region is, to a large extent, based on theoretical investigations; even the extension of the dust free zone is presently unknown. Nevertheless, dust in the solar vicinity yields the possibility of studying particle processing under extreme radiation and heat conditions. Local dynamical effects, like for instance as observed onboard ULYSSES in the Jupiter environment (/ll/), are discussed as special effects of cosmic dusty plasmas (/12/, /13/) an can also be expected in the solar environment. d These effects depend on the charge to mass ratio and are usually seen for submicron particles, which are not accessible to brightness observations. The probing from about 0.3 AU distance towards the very close vicinity of the sun creates the possibility of studying the properties of dust with decreasing solar distance and therefore increasing temperature. As shown in another paper (/14/), the study of cometary dust especially during its travel towards the sun could give new insights into cosmochemical relations, when an analysis of its elemental composition is achievable. YII ,1:3-H (3)99