This paper presents an experimental evaluation of a software-implemented fault tolerance (SIFT) environment built around a set of self-checking processes called ARMORs running on different machines that provide error detection and recovery services to themselves and to spaceborne scientific applications. The experiments are split into three groups of error injections, with each group successively stressing the SIFT error detection and recovery more than the previous group. The results show that the SIFT environment adds negligible overhead to the application during failure-free runs. Only 11 cases were observed in which either the application failed to start or the SIFT environment failed to recognize that the application had completed. Further investigations showed that assertions within the SIFT processes-coupled with object-based incremental checkpointing-were effective in preventing system failures by protecting dynamic data within the SIFT processes.