Optical communication between satellites in orbit requires highly accurate tracking of an incoming laser beam, to allow the generation of necessary control signals for the pointing mechanisms. For the SILEX system planned by ESA the tracking sensor is required to determine the position of the centre of the focused laser spot with a la noise error within 0.1,um on the CCD detector (equivalent to a mispointing of 0.07μrad), for the nominal bandwidth of 8kHz and the minimum optical power of 110pw. This implies the determination of the centre position to small sub-pixel accuracies, achieved via mathematical interpolation from the fractions of the optical signal falling in the centre 4 pixels. This paper updates a previous paper'. It discusses the development of the tracking sensor breadboards by BAe and Sira. The detector unit, which uses the new 14x14 pixel CCD developed by Thomson-CSF, provides for fine adjustments of the CCD position. It also houses the electronics for CCD output buffering and amplification. The electronics unit carries out the processing of the video signal, to determine the coarse position of the spot over the 14x14 pixel area, and a very accurate position over the central 2x2 pixel area via an algorithm executed in a microprocessor. The paper presents some performance results including new results from the second breadboard, and routes to the design of flight sensors.