 Subunit 1.5 summary. The unit summary, let's go back and recap a little bit about what we talked about in this first unit. So you've learned that system engineering is a rigorous approach to the design, creation, and operation of a system, end-to-end from high-level goal all the way through to an operational system. You've been introduced to some of the common definitions of system engineering, and we'll talk more about that in future units. We've discussed why system engineering is needed and the value that it brings to the development of large projects, and you've learned the consequences of poor system engineering. We've covered the roles of system engineers, you've learned what they do and how they work, and we've also covered the NASA system engineering engine as a model for how to coordinate system engineering. Congratulations, you made it to the end of Unit 1. You can now navigate to the Mars sample return mission page to start learning about the optional Mars sample return project that will run throughout the course. This project will be an opportunity for you to apply your knowledge to a mission that NASA has thought about accomplishing for many years, bringing samples back from Mars. You can also now take the Unit 1 quiz. To pass this course, completing this quiz and all the others is required. Remember that this quiz will count for 10% of your final grade, so study hard and good luck.