On February 16, 2024,  IFT secured an AFRL SBIR Phase II contract, titled “A Predictive Digital Twin for Integrity Monitoring of Multi-Source Positioning Navigation & Timing (PNT) Systems.” This contract addresses challenges in Global Navigation Satellite Systems (GNSS), particularly vulnerabilities to interference and spoofing, crucial in Defense-related scenarios. To overcome these issues, a family of robust methods exploiting multiple navigation sources will enhance PNT service reliability. The digital twin developed in Phase I serves as a realistic software testbed, facilitating the testing and validation of integrity monitoring methods for multi-source PNT systems. In Phase II, receiver autonomous integrity monitoring (RAIM) methods will be developed across GNSS receiver processing stages, aiming to significantly enhance performance against various types of PNT spoofing attacks. The final stage involves implementing these developed integrity monitoring methods in hardware receivers for testing and evaluation with real GNSS signals and spoofing attacks, marking a pivotal step in advancing multi-source PNT system reliability and security.