Overview
ISO 18427:2013 - Space data and information transfer systems - Spacecraft Onboard Interface Services - Subnetwork Synchronization Service - defines the SOIS Subnetwork Synchronisation Service interface provided by onboard subnetworks. The standard specifies the service and service interface only; it does not prescribe link-level mechanisms. ISO 18427:2013 adopts CCSDS 853.0-M-1 and is intended to be used together with the SOIS Green Book, promoting interoperable, reusable spacecraft onboard interface services.
Key topics and requirements
- Service definition and scope
- Formal definition of the Subnetwork Synchronisation Service for SOIS-compliant onboard subnetworks.
- Scope limited to service interface and behaviour; link implementations are out of scope.
- Service parameters and primitives
- Specification includes service parameters and synchronization primitives (operations) that a subnetwork must expose to users to synchronize to subnetwork-maintained time or asynchronous subnetwork events.
- Management Information Base (MIB)
- A MIB is defined for management and monitoring of the synchronization service.
- Conformance
- A Service Conformance Statement proforma is provided to document compliance with the recommended practice.
- Operational considerations
- Sections cover function, context, assumptions, quality of service (QoS) and security considerations relevant to applying the service in mission systems.
- Conventions
- Bit and octet numbering conventions and terminology consistent with CCSDS/OSI-based practice are used.
Applications and practical value
ISO 18427:2013 is applicable to any mission or equipment claiming to provide a CCSDS SOIS-compliant Subnetwork Synchronisation Service. Typical practical uses include:
- Synchronizing onboard subsystems (avionics, payloads, instruments) to a common subnetwork timebase for coordinated operations.
- Providing event synchronization for time-triggered activities, deterministic control loops, and coordinated payload sequences.
- Timestamping telemetry, logs, and science data consistently across subsystems for accurate post-processing and cross-supported missions.
- Enabling interoperability and reuse of software and hardware by providing a common service interface across different onboard data links.
Who uses it:
- Spacecraft system architects and avionics engineers
- Onboard software developers and middleware teams implementing SOIS
- Mission integrators and cross-agency projects relying on CCSDS interoperability
- Standards officers and test teams validating conformance
Related standards
- CCSDS 853.0-M-1 (adopted as the basis for ISO 18427:2013)
- Spacecraft Onboard Interface Services (SOIS) Green Book (guiding principles and overall SOIS architecture)
- Link-level protocols for providing the service (documented separately by missions, agencies, or CCSDS)
Keywords: ISO 18427:2013, SOIS, Subnetwork Synchronisation Service, spacecraft onboard interface services, CCSDS, synchronization, subnetwork time, MIB, service interface, onboard subnetworks.
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