We report a sun tracker sensor for attitude control of space navigation systems. The sensor exploits the concept of asynchronous operation previously devised by the authors for those devices. Asynchronous luminance sensors optimize sun trackers operation because only illuminated pixels are readout and can transmit data. This approach outperforms classic frame-based sun trackers in terms of bandwidth consumption, latency, and power consumption. The new sensor under study has been optimized for operation and interaction with other attitude control systems when it is embarked. The sensor power consumption is quite reduced. To save power, its pixels enter automatically in standby mode after gauging illumination levels. The device operates with only 0.45V. The pixel matrix has been devised to optionally be directly powered by energy harvesting systems based on photovoltaic diodes connected to a storage capacitor without a DC-DC converter.