If a spacecraft fails then the mission is unlikely to be repeated for years, if ever. Spacecraft must therefore be highly reliable, first surviving the harsh vibration environment of launch, and then operating successfully for long lifetimes without servicing and despite large radiation doses. The design and manufacturing processes must be rigorous, ensuring the correct operation of the spacecraft the first and only time it will be used. The systems and electronics are analysed down to a component level to ensure that the failure of any particular constituent part will not jeopardise the longevity of the whole mission. Design concepts must also be continually re-examined to verify their validity.
Construction is to the highest quality with no expense spared.
The current design trend is towards simple, well-tested, conservative design, producing large, heavy systems that ignore new technologies. This further spirals mission costs the size and cost of the launcher being proportional to the size and mass of the spacecraft. High spacecraft and launch costs also affect the cost of mission operations. Support teams monitor spacecraft around the clock, to ensure continuing operation. At the first signs of failure, a network of experts is assembled to ensure that the best expertise is available to deal with ensuing problems.