[P-PS03] Small Solar System Bodies: New perspectives on the origin and evolution of the Solar System

[PPS03-15] Prediction of detected ions by the ion analyzer equipped with the Comet Interceptor using a photochemical reaction model

*Ryo Tao¹, Satoshi Kasahara¹ (1.The university of Tokyo)

Comet explorations have been conducted in the past, but there has been no direct exploration of a long-period comet among comets. Long-period comets are thought to have originated in the Oort cloud and are likely to retain primordial features from the early stages of solar system formation. Understanding this is expected to provide important clues to the origin of the solar system. The Comet Interceptor Mission, jointly planned by ESA and JAXA, will conduct the first in-situ measurements of a long-period comet or interstellar object. The scheduled launch is in 2029, and its scientific goal is to characterize the surface composition, shape, composition, and coma environment of the target comet. The spacecraft will temporarily wait at the L2 Lagrange point, and once the target comet is determined by ground-based observations, it will approach and conduct flyby observations. The ion analyzer onboard Comet Interceptor will measure the mass, energy, and direction of cometary ions in the coma. These data are obtained when the comet probe passes through the coma of the target comet. On the other hand, the coma will also contain dust particles, and therefore a dust shield must be installed on the ram side to prevent damage to the instrument. However, if the ram direction is completely covered, incoming cometary ions are also blocked. Therefore, we will make a small aperture in the dust shield to allow cometary ions to enter. In determining the size of this hole, it is necessary to estimate the number density of ions of long-period comets to estimate the inflow into the ion analyzer. We derived the ion number density profile of the coma by numerical calculation using a photochemical reaction model of cometary gas. However, since the target object is determined after launch, we cover a broad range of the production rate from ~10³¹s^-1 to ~10²⁵s^-1. We estimate the time evolution of the ion number density detected by the ion analyzer for each ion species and predicted the cometary ion influx. The ion number density profile obtained here can also be useful for analyses of acquired data. Gas production rates of the explored object can be estimated from the ion measurement via these model calculations.