Reliability prediction and simulation for a communications-satellite fleet

Telecommunications satellites are usually designed to operate in-orbit for as long as 10-15 years. This places a lot of focus on the reliability of the spacecraft from the early design phase, through the manufacturing process and up until after the spacecraft has been launched and put into service. In this paper, the authors discuss methods with primary focus on the reliability of an in-orbit satellite fleet, i.e. a collection of satellites that have been placed successfully in orbit. Traditional methods developed primarily for reliability predictions of a single satellite with no flight history are not adequate for this purpose. Realistic reliability predictions for an in-orbit satellite fleet must address the flight history (launch date and observed in-orbit failures) of each individual satellite, and furthermore spacecraft units are often observed to have nonconstant hazard rates, significantly different from those that can be calculated using military handbooks. To obtain reliability predictions for a satellite fleet with individual flight histories, nonconstant unit hazard rates, and complicated redundancy configurations, Monte-Carlo simulation is a very useful tool, because it can handle complex models in contrast to most analytical tools.