Passive sensor countermeasures development requires a full electromagnetic spectrum defense (RF, EO, and IR), defending against single mode, multimode, and multi-band threats. Threat weapon systems are evolving at a rate faster than the development/test communitys typical acquisition cycle. Therefore, to reduce the number of acquisition cycles, a modern, open, flexible, and modular dual mode seeker surrogate is vital to the USG to keep up with and, hopefully, outpace our adversaries. For commercial applications such as air surveillanceFAAand the automotive industrycollision avoidance and autonomous controldual mode sensors offer a very robust solution to the sensor measurement accuracy and all-weather capability requirements. Leveraging AMSs experience and expertise in air and missile defense technologies, command and control, radar systems, seekers, threat exploitation, modeling & simulation, and prototype hardware development and testing, AMS proposes a Phase I approach for a multimode RF/IR seeker surrogate which consists of requirements definition (informed by algorithms, CONOPs, and Use-Cases), RF/IR sensor design, RF/IR system design (integration), and risk identification/mitigation that, upon completion, will lead into a Phase II prototype development and testing.