A special mode of application of non-destructive assay or C/S measures or a combination of these, that operates for extended periods without inspector intervention. The use of unattended safeguards instruments has long been a part of IAEA safeguards. Optical surveillance used to monitor an area for safeguards relevant activities over extended periods is unattended. Unattended radiation detection sensors are used to monitor the flow of nuclear material in a facility process area. For unattended monitoring, certain criteria must be met, including measures to ensure data authentication and encryption