1. A computer system for determining a survivability aspect control signal for an aircraft, said computer system comprising: a processor; and a memory including software instructions adapted to cause the computer system to perform the steps of: (a) providing a plurality of signature exposure models, each signature exposure model corresponding to a threat sensor and including a threat sensor characteristic and a threat operational characteristic; (b) selecting a mission portion; (c) selecting, based on the selected mission portion, a plurality of the provided signature exposure models; (d) calculating a signature exposure index based on the plurality of the provided signature exposure models and the selected mission portion; and (e) providing a survivability aspect control signal based on the signature exposure index.