ASRI proposes to develop an advanced and commercially viable Non-Intrusive Vibration Monitoring System (NI-VMS) which can provide effective on-line/off-line engine vibration monitoring capabilities without relying on intrusive key-phasor speed measurements. Many powerful vibration signature analysis techniques for engine-health monitoring rely on key-phasor signals to extract/enhance critical fault signatures from noisy vibration measurements. In many situations (e.g. SSME HPOTP), such speed measurements are not available, usually due to the safety concerns of a key-phasor's intrusive installation (e.g.in a high-pressure liquid-oxygen environment for HPOTP). As a result, the ability/reliability for health monitoring and post-test diagnostic evaluation is severely limited. The proposed NI-VMS overcomes this problem by utilizing a novel signal analysis technique called Pseudo Key Phasor (PKP) to reconstruct a PKP signal directly from external vibration measurements. This procedure enables powerful signal analyses that require a key phasor to become applicable, greatly enhancing fault detection and diagnostic capabilities. NI-VMS can reduce the risks of catastrophic engine failure and improve the reliability of NASA's current/future propulsion systems. Phase I feasibility studies using SSME test data have successfully demonstrated the technical merits of NI-VMS. Phase II will complete design, development, and testing of the prototype NI-VMS hardware/software system.