Which agency is responsible for periodically calibrating test, measurement, and diagnostic equipment (TMDE)?

The Precision Measurement Equipment Laboratory (PMEL) is the correct choice because it is specifically tasked with the calibration of test, measurement, and diagnostic equipment (TMDE). PMELs ensure that these instruments maintain accuracy and reliability, which is critical for operational effectiveness in various military applications. They implement standardized procedures to calibrate, certify, and maintain the TMDE, thereby ensuring compliance with military specifications and national standards.

In contrast, the Aircrew Flight Equipment office primarily focuses on the management and maintenance of aircrew equipment rather than calibration services. The Equipment Maintenance Squadron may handle maintenance and repairs of broader equipment but is not dedicated to the calibration of TMDE. The Defense Logistics Agency, while it plays a vital supply chain role in managing logistics and resources, does not perform the calibration tasks that PMELs are specifically designed for. Thus, PMEL's defined role in calibration makes it the correct agency for this responsibility.