As a general trend , the complexities of modern spacecraft are increasing to include more ambitious mission goals with tighter timing requirements and on - board autonomy . As a byproduct , the protective features that monitor the performance of these systems have also increased in scope and complexity . Given cost and schedule pressures , there is an increasing emphasis on understanding the behavior of the system at design time . Formal test - driven verification and validation ( V&V ) is rarely able to test the significant combinatorics of states , and often finds problems late in the development cycle forcing design changes that can be costly . This paper describes the approach the SMAP Fault Protection team has taken to address some of the above - mentioned issues .