Abstract: A system includes a subsurface safety valve assembly connected to a production tubing string and including a sensor assembly disposed on its outer surface. The sensor assembly includes a magnetic sensor configured to measure a magnetic field or a sonic sensor configured to measure a sonic signal, and is configured to measure a change in a parameter caused by change in position of a closure member that is configured to selectively permit fluid flow through the central bore of the subsurface safety valve. The system further includes a control unit positioned at a surface location and that is configured to receive, from sensor assembly, a measurement of the change in the parameter, wherein the measurement is a change in the magnetic field or a change in the sonic signal.