The analysis postulates an algorithm for adaptively varying the target-track update rate as a function of target manoeuvring. The algorithm proposes to vary the target observation time interval by an amount that tends to maintain a constant residual error. As an example, the algorithm is shown to be implemented with a two-dimensional alpha-beta filter. Simulated results are calculated for a target manoeuvre consisting of a single 90° turn. The results show that when a manoeuvre is detected, the sampling time interval can be reduced rapidly to facilitate tracking with reduceed error. After the manoeuvre, the sampling interval is increased automatically so more time can be made available to the phased array radar for other activities.