The volume directory file is the first file of every logical volume. It is composed of a volume descriptor record, a text record and a series of file pointer records. The volume descriptor record identifies the logical volume and the number of files the logical volume contains. A text record follows the volume descriptor record and identifies the type of data contained in the logical volume. There is a file pointer record for each data file of the logical volume, indicating each file's class, format, and attributes.
All logical volumes have a volume directory as the first file.
This is followed by leader, image, and trailer data files and is concluded with a null volume directory. When a logical volume is split between physical volumes, the volume directory is repeated at the start of the continuation tape. A small piece of reflective tape is located on the non-recording side of a CCT several feet from the beginning of each reel. A small piece of reflective tape is located on the non-recording side of a CCT several feet from the end of each reel. Beginning in the spring of 1979, the MSS sensor aboard Landsat 3 began to experience a problem with proper synchronization of scan lines.