To address NASA's need for in situ sensor systems for use on rigid and/or flexible ablative Thermal Protection System (TPS) materials, Physical Optics Corporation (POC) proposes to develop a novel Embedded Multifunctional Optical Sensor (EMOS) system providing accurate in situ measurement of multiple thermal protection system (TPS) structural, aerothermal, and aerodynamic response parameters including temperature, heat flux, and pressure. The EMOS is based on use of novel materials for high-temperature operation and uniquely designed fiber optic microsensors. The EMOS system is capable of simultaneously measuring multiple TPS response parameters (e.g., pressure, temperature, and heat flux) using a suite of miniature (diameter <400 micron) fiber optic Fabry-Perot (FP) interferometric sensors. EMOS will tolerate operating temperatures >1500 degrees C and measurement errors within 0.4% for temperature sensors, 0.2% for pressure sensors, and 20% for heat flux measurement. In Phase I POC will demonstrate the feasibility of EMOS for in-situ measurement of TPS responses in an aerothermal environment by fabricating and testing a technology readiness level (TRL)-4 prototype, with the goal of achieving TRL-6 by the end of Phase II.