High Quality Content by WIKIPEDIA articles! The Saturn V Instrument Unit is a ring-shaped structure fitted to the top of the Saturn V rocket`s third stage (S-IVB) and the Saturn IB`s second stage (S-IVB). It was immediately below the SLA (Spacecraft/Lunar Module Adapter) panels that contained the Lunar Module. The Instrument Unit contains the guidance system for the Saturn V rocket. Some of the electronics contained within the Instrument Unit are a digital computer, analog flight control computer, emergency detection system, inertial guidance platform, control accelerometers and control rate gyros. The instrument unit (IU) for Saturn V was designed by NASA at Marshall Space Flight Center (MSFC) and was developed from the Saturn I IU. NASA`s contractor to construct the Saturn V Instrument Unit was International Business Machines (IBM).