Integration and test of the REgolith X-ray Imaging Spectrometer and recommendations for low-cost, high-risk spaceflight programs

Abstract

NASA Risk Class D programs must meet their technical goals with limited resources. The Regolith X-Ray Imaging Spectrometer (REXIS) is a Class D student collaboration instrument flying on the NASA OSIRIS-REx mission. This thesis describes and analyzes the NASA management and systems engineering processes that were tailored for REXIS. Part of the Class D approach is to accept more risk to meet schedule and cost requirements. This added risk is carried into the Integration and Test (I&T) phase, and can manifest in an off-nominal sequence. The REXIS I&T phase is examined in detail to provide insight into the resource tradeoffs necessary to successfully deliver a Class D instrument. Each step of the I&T sequence is portrayed, including critical incidents that arose during this phase and how they were handled. The I&T process of the REXIS Radiation Cover Deployment System is described in detail, and recommendations are made to further reduce the risk on this critical system. Three key lessons from REXIS I&T are presented to help inform future low-cost, high-risk missions. First, challenges arise when inevitable changes occur between the Engineering and Flight Models. Secondly, procuring flight spare hardware for Class D missions is highly valuable. Finally, small co-located teams ease communication and lessen the burden of documentation, but can have limitations in expertise and flexibility during critical phases.