EXOMARS TRANSFER AND APPROACH PHASE NAVIGATION

摘要

This paper summarizes some mission analysis results obtained for the ESA ExoMars mission design phase B1. The current baseline considers a single launch in 2011 with a Soyuz-Fregat 2-1b mid-sized launcher vehicle from Kourou onto a GTO. Injection into the interplanetary Earth-Mars trajectory will be provided by four in-plane perigee manoeuvres implemented with the spacecraft propulsion system. A 2-years delayed transfer trajectory will be used to reduce the risk to the mission associated with a global Mars dust storm. This strategy will present some challenges for the navigation and guidance of the final approach phase and release of the descent module from the hyperbolic arrival trajectory due to the high Earth range (2.5 AU) and a superior conjunction 45 days before the arrival. Preliminary studies have been conducted to determine the accuracy achievable on the flight path angle at the Mars atmosphere entry and to estimate the required AV for the entry point targeting. Furthermore the beneficial effect of including ADOR measurements has been assessed. In order to further improve the delivery errors at the entry point, the targeting strategy has to include a last correction manoeuvre as close as possible to the Mars arrival while ensuring enough time to perform the descent module deployment.