This report presents the results of a pre-study to specify sensors for stealth UCAV. The sensors that have been analyzed are noise radar based SAR, an IR-sensor and laser radar. The main function of the SAR-sensor is to detect targets at a far distance and then queue the IR-sensor or laser radar to these detections. The task for the IR and laser radar is then to recognize and identify the objects at ranges from 2 - 5 km for target selection. To achieve this, the laser radar should have a scanning 512x1 array detector and the IR should have a 640x480 element sensor, the optics should give a 1 degree field of view. It has not been possible to select the wavelength for the IR with the criteria investigated here. The sensors´ ability to work under different weather conditions has been investigated and three different weathercases have been defined: clear weather, rain and fog. The results show that all sensors are capable of handling the clear weather case. In rainy conditions, both the IR and the laser radar fail due to low atmospheric transmission, leaving only the SAR working under these conditions. With 20 m ground based fog, the range at which the IR and laser radar are able to identify a target is reduced. With a fog cover (base at 200 m) both IR and laser radar fail due to low transmission. The radar sensor´s ability to function under all of the investigated weather conditions shows the need of multi sensor functionality for UCAVs as well as for surveillance UAVs.