Systematic reliability improvements on the GRAIL project

This paper describes the system engineering processes used on the GRAIL mission to both improve the probability of mission success and the overall reliability. The GRAIL mission is a Discovery class mission designed to map the gravity field of the moon in 2012 during a 3 month science collection period. The mission requires two spacecraft to fly in formation to obtain ranging data between the spacecraft. The ranging data constitutes the science data set which is then analyzed to create the lunar gravity solution. These spacecraft are largely single string, requiring that they have high reliability. The short data collection window of 3 months requires that the spacecraft also have high availability during the data collection period. During the formulation phase (Phase B) of the GRAIL project, the project team implemented a multi-prong approach to identify potential issues with the conceptual (Phase A) design. The project team assessed each of these issues and implemented changes which were deemed cost effective and technically feasible. The processes used and resulting decisions made during the formulation phase to identify, assess and implement potential reliability improvements to the GRAIL mission as well as the resulting design are the focus of this paper.