Speaker
Mr
Nuno Silva
(Critical Software)
Description
Activity: TRP
TO: Claudio Monteleone/Data Systems Division
The scope of the work is the dependability assessment of on-board space computers (OBC) and approaches applied to achieve high reliability and availability of such systems, in order to provide a consolidated solution for the following objectives:
- establish generic requirements for the procurement or development of OBCs with a focus on well-defined reliability, availability, and maintainability requirements and study means, and
- provide recommendations to support the association of dependability figures to OBC configuration items throughout their life cycle (e.g. for allocation, prediction or assessment of dependability).
The results of this activity are applicable to a typical OBC of the following mission domains:
- Science and Earth Observation missions;
- Telecom missions;
- Commercial earth observation missions
Generic requirements for OBCs have been established taking into account the ongoing ESA study "Avionics System Reference Architecture" (ASRA). The requirements cover both functional aspects as well as non-functional aspects. The requirements identify details that have a particular impact on reliability and/or availability and are generic enough to be applicable for a typical OBC in an unmanned, non-launcher spacecraft (e.g. an earth observation satellite, a telecom satellite or the deep space probe of an interplanetary science mission).
A dependability plan has been then established describing the activities, processes and procedures to be executed to provide assurance of the dependability characteristics of OBCs. The identified plan also provides a life-cycle model for OBCs and its associated outcomes.
A technical note has been produced to provide a set of guidelines about associating dependability figures to computer configuration items throughout their life cycle. It covers the technical approach for measuring the dependability of OBCs, including:
- all the phases of the lifecycle of OBCs;
- configuration item levels from basic part to set levels;
- computer hardware, software and their integration;
- theoretical and practical aspects of dependability measurement.
A set of recommendations written in semi-formal language have been provided for measuring the dependability of OBCs. The recommendations have been established for associating dependability figures to OBC configuration items throughout their life cycle, such that it can be reused, totally or in part, for the procurement or development of OBC configuration items.
A technical note has been produced to cover the approach for demonstrating the dependability of OBCs throughout the their lifecycle, including theoretical and practical aspects. Several aspects of the HW/SW life-cycle that have impact on the OBC dependability are covered.
Finally an existing ESA mission has been chosen as an application case in order to validate the approach. In this application case, the dependability has been measured and the dependability assurance activities proposed have been practically applied.
