This report summarises the FOI´s research during 2001 on Reconnaisance and Surveillance including Low Observables. The research comprises sensors, datafusion, sensor signal processing, modelling, measurements and material technology for low observables. Sensor applications are mainly based on the utilization of radar, laser and infrared systems. Radar research has been focused on the development of an experimental system in the frequency band 200 - 800 MHz for SAR and GMTI, and a demonstrator for an array antenna ("DBF smart skin array). Research on electro-optical systems are aiming at combinations of active and passive techniques and also multispectral applications in detection and classification. A data fusion system, applying EO-sensor data is being developed for ground target recognition. Modelling and measurements of radar signatures describing the interaction of targets and background have been performed. During the year a database containing IR and visual sensor data from background registrations was completed. Validation of Sensorvision synthetic data (a real-time simulation software for virtual IR-environments) indicates a good correlation in comparison to experimental data. IR polarization signatures have been measured. Material research on low observables has involved: properties combining radar absorption and high-temperature durability, and also material properties that reduces object signatures for both radar and infrared sensors.