ESA PREPARATORY PROGRAM FOR THE ROSETTA CNSR MISSION

The paper reviews the progress made on the definition of the design and on the development of the technologies for the Comet Nucleus Sample Return mission, known also as ROSETTA. This mission is a Cornerstone in the scientific programme of ESA and it is being planned as a collaborative project with NASA for a baseline launch around 2001. The main mission objective is to collect and to return to earth samples from a comet nucleus for study in terrestrial laboratories. These studies would greatly advance both planetary science and astrophysics. The paper provides an outline of the baseline mission and discusses its critical phases. Next it presents the agency's preparatory programme, which is addressing the definition and the development of the novel techniques and technologies necessary to implement the proposed operational strategies. The most demanding mission aspects are: the comet approach and landing phase, where the spacecraft must safely and accurately land on a comet with poorly known dynamic and shape characteristics; the sample acquisition phase, where surface and subsurface samples must be collected in a milli-g environment from a comet nucleus with poorly known composition and texture; and the Earth re-entry and sample recovery phase, where the aerocapture of the re-entry vehicle must be achieved, within stringent thermal and dynamic constraints, to an accuracy that allows a rapid recovery of the sample. The paper reviews progress achieved in the definition of: 1. guidance, navigation and control strategies and techniques which meet the requirement of safe and accurate landing on the comet and at the Earth; 2. the sample acquisition and anchoring facility which has the capability of collecting and handling surface and core samples down to 3 m depth; 3. preparation of comet nucleus analogue materials for sampling performance verification; 4. approach and landing instrumentation, including penetrator-carried RF beacons to be fired into the comet nucleus for providing an artificial landmark; 5. thermal protection and descent system, including the heat shield and the parachute for the final Earth re-entry phase; 6. the harpoon, which should provide a back-up sampling scenario, should landing not be safe; and 7. the electric propulsion, which could provide more flexibility in the planning of solar system exploration missions.