The traditional way of providing software to support space missions has been to build custom systems from scratch and then modify them to accommodate changes (the process of “software maintenance”). With the improving availability of Commercial Off-the-Shelf (COTS) software components, using COTS components extensively in building and maintaining systems is a new alternative. While we have nearly always used some COTS software components, now we can use them much more in systems associated with the exploration and settlement of Mars. Using COTS software components has both pros and cons. The major pros can include: 1. Lowers the cost to build and maintain the system 2. Shortens the time to build the system 3. Encourages the use of open standards in building and maintaining the system 4. Eases using “spare parts” during maintenance, and reuse during development 5. Makes component interactions more explicit 6. Encourages encapsulation, table-drive, and instrumentation.

The major cons can include: 1. Requires either customizing the software to fit the way people want to work, or making the way people work fir the COTS software 2. Constrains the kinds and forms of changes in systems 3. Slows making changes in the system 4. Adds to the diversity of styles, conventions, and practices in the software 5. Increases the difficulty and cost of making functional enhancements 6. Lengthens the time to find and fix performance faults and shortfalls.

Given Mars mission requirements and eventualities, achieving a balance between the pros and cons in using COTS software components involves making tradeoffs. Implementing them includes the se of tailoring code, wrappers, reuse, and certification.