Published online by Cambridge University Press: 23 November 2009
To fulfill any specific task a certain navigation accuracy is in general required. If this requirement can be achieved by different systems the cost effectiveness will be decisive. Apart from missions which allow large position errors, medium or high navigation accuracies will normally be desired, obtained either by high technological standards or by an unsophisticated system with an updating procedure. The cost of highly sophisticated systems increases exponentially with increasing accuracy, so that our object was to find an appropriate updating system.