They also are not regularly read, so there is concern about aging. A process of archiving the K-line data has been devised. This is based on C source code originally written by R. Ronan.
Tapes have occasional errors that require repeated reads to capture.
This slows the process. Some corrections are only approximate, if the clock is reset too frequently to permit accurate determination. Save the calibration images and a sample image. Check the tape and copy. A random sample of the tapes is made to verify correct operation.