FTC electronic boxes (yellow) and MSU (red) in ATV avionics bay
The Monitoring and Safing Unit (red) and Fault Tolerant Computer electronic boxes (yellow) inside the ATV's avionics bay

Dependability

Did you ever miss an important date because your car failed on the road, or lost your work because your laptop broke down or just missed the end of a good movie because your TV screen went dark? If the answer is “yes” you may wonder what is done to make sure that products are reliable and these things do not happen too often. Any product - such as a car, a laptop or a satellite – is generally expected to work successfully for a required period of time.

It is the responsibility of dependability engineers to ensure, as much as possible, that products are reliable and function as expected (for example over 100.000 kilometres in the case of a car, 50.000 hours for a laptop, or the multi-year duration of a space mission), or work when needed and can be repaired after failure.

In the space domain, dependability engineers put their efforts to ensure for example that the satellite on-board computers are reliable, weather maps are available to the news (such as from the Meteosat satellites), and on-ground infrastructure required to operate and control in orbit satellites can be repaired in case of failure.

What is the Dependability domain?

Dependability covers the engineering disciplines Reliability, Availability and Maintainability. Reliability is focused on the capability to function without interruption, Availability is the ability to operate when needed and Maintainability refers to the easiness of repairing/replacingor upgrading the product.

Ensuring dependability is always a trade-off with other and mostly conflicting requirements such as safety, security, mass, cost, schedule, etc. For example, one possible way to increase reliability is to have the same function being performed by two equal but independent systems which in the end results in a final product with a higher mass.

Dependability and safety within ESA are integrated disciplines covering satellites (hardware, software), as well as ground infrastructure and operations (human aspects). It encompasses many areas of expertise and scientific knowledge throughout the life cycle phases of a space project.

Last update: 10 December 2012

Copyright 2000 - 2014 © European Space Agency. All rights reserved.