A target tracking device incorporating a Position Sensitive Detector (PSD) 1 is described. A target is illuminated by a laser of a suitable wavelength. The target reflects the laser radiation and the reflected radiation is incident on a flying vehicle carrying a target tracking device. The PSD in the device outputs a signal representative of the position of the incident laser spot. The output signal is input into control electronics, the control electronics incorporating a resistive transimpedance amplifier. A higher than usual bias voltage is applied to the PSD yielding improved pulse response of the target tracking device. Therefore, the tracking device is particularly suited for use with a target marking laser having a short pulse duration.