Overview
ISO 18426:2013 - Space data and information transfer systems - Spacecraft Onboard Interface Services - Subnetwork Memory Access Service - defines the Subnetwork Memory Access Service as part of the Spacecraft Onboard Interface Services (SOIS) family. Adopted from CCSDS 852.0-M-1 (Magenta Book, Dec 2009) and published by ISO in 2013, the standard specifies the service interface for reading and writing memory locations or memory blocks distributed across an onboard subnetwork. It defines what the service must provide (not how it must be implemented on specific data links), and is intended to be used with the SOIS Green Book.
Key Topics and Requirements
- Service definition only: Specifies the Subnetwork Memory Access Service interface and behaviour; implementation protocols for specific onboard data links are out of scope and are to be documented separately by missions, agencies or CCSDS.
- Memory access operations: Covers primitives and parameters needed to perform direct read/write access to distributed memory resources (single locations or blocks), including management interfaces.
- Service parameters and primitives: Describes the required service parameters and the set of service primitives (request/response semantics) for memory access.
- Management Information Base (MIB): Defines a MIB that lists management objects and configuration options relevant to the service and supports monitoring and control.
- Quality of Service (QoS) and security considerations: Addresses QoS and security aspects conceptually, consistent with SOIS principles (details depend on the link/protocol implementations).
- Conformance and documentation: Includes a Service Conformance Statement Proforma to declare compliance for missions or equipment claiming SOIS Subnetwork Memory Access Service support.
- Conventions: Uses CCSDS conventions such as bit-numbering (Bit 0 = first transmitted MSB) and octet-based data organization.
Practical Applications and Who Uses It
ISO 18426:2013 is aimed at organizations and professionals involved in spacecraft onboard systems where distributed memory access is needed:
- Spacecraft systems engineers and avionics architects designing onboard data-handling subsystems.
- Firmware and protocol developers implementing SOIS-compliant services over CAN, SpaceWire, Mil-STD-1553, or other onboard links (protocol specifics are defined per link).
- Mission integrators and agencies ensuring cross-support and interoperability across multi-agency or cross-mission hardware and software.
- Procurement and compliance teams documenting conformance for payloads, OBCs, and distributed devices.
- Vendors of onboard devices (sensors, actuators, instrument electronics) that expose memory-mapped registers accessible via subnetwork services.
Related Standards
- CCSDS 852.0-M-1 (original Recommended Practice)
- SOIS Green Book (conceptual principles and framework)
- Link-level protocols and CCSDS documents that specify how to carry the memory access service over specific onboard data links
Keywords: ISO 18426:2013, Subnetwork Memory Access Service, SOIS, CCSDS 852.0-M-1, spacecraft onboard interface, memory access, MIB, service conformance, onboard subnetwork.