Skylab Operations Handbook Command/Service Modules CSM 116 Thru 118: Command and Service Module Description - Volume 1The SKYLAB Operations Handbook (SOH) is a contractual document. The SOH (Volume 1) is system-oriented and not specifically designed for utilization by any special group. Volume 1 is the description portion of the SOH. It provides the description of all Command-Service Module (CSM) systems.