Dependability

Dependability is collective term used to describe the availability performance and its influencing factors reliability, maintainability and maintenance-supported performance.

During its utilisation phase, a space system and its constituents may be adversely affected by faults originating in the environment, yielding to periods of correct service delivery and possible outages.

Performance requirements

Although dependability performance requirements vary with space applications (e.g. launchers, exploration, human space, telecom, earth observation), on-board computers provide capabilities that are often critical for a space mission. The on-board computers handle the executions of the computer programs, and manage information exchanges with the other equipment units within the spacecraft or with the external (e.g. electrical ground support equipment, launcher, ground segment).

Technology

The harmonisation policy of ESA asks for the deployment of enhanced and homogeneous industrial processes in the area of avionics embedded systems and on-board computers for the space industry. In parallel the SAVOIR (Space Avionics Open Interface Architectures) initiative, intends to federate initiatives towards avionics standardization and innovation and to help concentrate all the efforts from industry, national agencies and ESA towards shared objectives.

In the execution of this policy as series of technology activities are programmed to support dependability assurance throughout the lifecycle of on-board computers:

• establishment of requirements for the procurement or development of on-board computers with a focus on well-defined dependability requirements;
• development of an avionics testbed for early verification of failure detection, isolation and recovery;
• raise of technology readiness level in the area of highly reliable and highly available COTS based computers.