Testing Early and Often: End-to-End Testing on the Double Asteroid Redirection Test (DART)

The NASA Double Asteroid Redirection Test (DART) is a technology demonstration mission designed, built and operated by the Johns Hopkins Applied Physics Lab (JHU/APL). The mission's primary objectives are to 1) achieve a hypervelocity kinetic impact with the secondary member of the binary asteroid (65603) Didymos and 2) downlink at least two images of the target with a pixel sample distance of 66 cm or better. Impact guidance is achieved using the onboard Small-body Maneuvering Autonomous Real-time Navigation (SMART Nav) system developed by JHU/APL. The SMART Nav system ingests images from an onboard imager, performs image processing and ultimately guides the spacecraft to impact. In parallel to SMART Nav operations, the spacecraft streams images back to the ground in real-time. At least two images are required from the last twenty seconds of imaging to achieve the desired pixel sample distance. Both onboard guidance and realtime image streaming drive strict data latency requirements. These requirements are levied across multiple subsystems and interfaces, making verification challenging. The highly-integrated spacecraft design and compressed integration schedule also preclude DART from fully testing these data-streams on the flight system before launch. DART has prioritized an early, end-to-end system-test effort with engineering model components and high-fidelity testbeds to address these concerns. This risk reduction effort seeks to demonstrate critical interfaces with adequate data latencies before the start of the Spacecraft Integration and Test phase (I&T). This paper describes 1) the overall mission and spacecraft image processing and downlink driving requirements, 2) the resultant architecture, 3) the risk reduction philosophy and 4) the demonstration plan and early results.