Optical Navigation for Lunar Transportation Systems Contingency Scenarios

Abstract

Transportation systems able to support the future human exploration of the Moon are currently under investigation in Europe. These systems must ensure a safe return of the crew for a variety of contingency scenarios, including the loss of ground-based navigation. Optical measurements may be used to support on-board autonomous navigation for these cases. The paper describes the architecture and algorithms needed for candidate system concepts for optical autonomous navigation (including different sensors and types of processed measurements), and presents the expected performances of the proposed systems for a variety of contingency scenarios. I. Introduction dvanced space transportation systems will be needed to support the human exploration of the Moon in the coming decades. These systems are currently under investigation in Europe in the frame of the Crew Space Transportation System (CSTS) preparatory program. Several technology research projects are being conducted to develop the key technologies required for the CSTS. This paper summarizes the preliminary results of one of these projects, which is aimed at investigating optical autonomous navigation systems for manned lunar missions. Flight and crew safety considerations impose severe requirements on the design of manned missions. The system must be able to cope with potential off-nominal or emergency situations. For instance, a number of contingencies may lead to the loss of the ground trajectory navigation or of the ground-spacecraft communication link. In both cases, the required maneuvers cannot be uploaded to the spacecraft, risking mission success or even crew lives if the failure occurs at a critical phase or lasts long enough. Therefore, an autonomous GNC becomes mandatory to mitigate those risks to acceptable levels, and such a backup needs an autonomous navigation function. In a LEO mission, autonomous trajectory determination may be feasible with GNSS equipment, but the availability of GNSS signals cannot given for granted over a whole mission to the Moon. Hence, a different autonomous navigation means is needed for the cis- and circumlunar space. One of the potential techniques for providing the required autonomous navigation solution is optical navigation, which is based on the sighting of point targets (stars or far bodies) and/or extended targets (close bodies). Optical navigation has the advantage that it does not require the use of any external, pre-existing navigation infrastructure (such as beacons or other spacecraft). Additionally, the concept has been already demonstrated in-flight during the Apollo program. Candidate systems for optical autonomous navigation for manned lunar missions are described in terms of the type of processed measurements and the sensors required. The performances of one of these system concepts are presented.