File:Saturn V instrument unit CCS transponder.jpg

English: Just arrived from Alabama, and made by Motorola in Scottsdale. My Dad was able to immigrate to America by working at that same facility in 1966.

The Saturn Instrument Unit (IU) was a squat cylindrical ring atop the Saturn IB and Saturn V S-IVB stage, and contained the guidance, navigation, and control equipment responsible for managing all Saturn stage functions from the launch pad, into earth orbit and in the case of the Saturn V, on to a lunar trajectory. It also contained telemetry, communications, tracking, crew safety , electrical power and environmental control systems. It kept the rocket going after lightning strikes on Apollo 12 caused the Command Modules systems to restart.

This gold-plated Command Communications System (CCS) provided for digital data transmission from ground stations to the Launch Vehicle Digital Computer (LVDC). This communications link updated guidance information and commanded other functions through the LVDC.

The CCS equipment, located in the IU, consisted of transmitting and receiving antenna systems (directional and omni), antenna switching elements (coaxial switches, hybrid rings and power divider), an S-band transponder, and the command decoder, which precluded unauthorized command data entry.

Command messages were transmitted from the unified S-band ground stations on a carrier frequency of 2101.8 MHz, modulated by a subcarrier of 70 kHz, which was modulated by a digital message. The transmitted message was received by the airborne transponder, where demodulation was accomplished. The resulting digital message was passed on to the command decoder, where it was checked for authenticity before being passed to the LVDC.

An artifact in the Future Ventures 🚀 Space Collection.