ISO 18423:2013 provides a Recommendation for Space Data System Standards in the area of transparent and regenerative Pseudo-Noise (PN) ranging systems. The PN ranging system is used to measure the round-trip light time between a ground station and a spacecraft. Regenerative ranging is primarily relevant for low Signal-to-Noise Ratio (SNR) cases like those seen in deep space missions; transparent ranging is more suitable for high SNR cases or when high accuracy ranging is not required.

ISO 18423:2013 defines both transparent and regenerative PN ranging systems for non-data relay satellite users. The specification for PN code components and generation, on-board spacecraft regenerative/transparent processing, ground station processing, and uplink and downlink signal modulation are defined. ISO 18423:2013 does not specify individual implementations or products, implementation of service interfaces within real systems, or the management activities required to configure and control the protocol.