From the 16th to the 27th of May 2005, a NATO Advanced Study Institute entitled Multisensor Data and Information Processing for Rapid and Robust Situation and Threat Assessment was held in Albena, Bulgaria. This ASI brought together 72 people from 13 European and North American countries to discuss, through a series of 48 lectures, the use of information fusion in the context of defence against terrorism, which is a NATO priority research topic.

Information fusion resulting from multi-source processing, often called multisensor data fusion when sensors are the main sources of information, is a relatively young (less than 20 years) technology domain. It provides techniques and methods for:

1) integrating data from multiple sources and using the complementarity of this data to derive maximum information about the phenomenon being observed;

2) analyzing and deriving the meaning of these observations;

3) selecting the best course of action; and

4) controlling the actions.

Various sensors have been designed to detect some specific phenomena, but not others. Data fusion applications can combine synergically information from many sensors, including data provided by satellites and contextual and encyclopedic knowledge, to provide enhanced ability to detect and recognize anomalies in the environment, compared with conventional means. Data fusion is an integral part of multisensor processing, but it can also be applied to fuse non-sensor information (geopolitical, intelligence, etc.) to provide decision support for a timely and effective situation and threat assessment.

One special field of application for data fusion is satellite imagery, which can provide extensive information over a wide area of the electromagnetic spectrum using several types of sensors (Visible, Infra-Red (IR), Thermal IR, Radar, Synthetic Aperture Radar (SAR), Polarimetric SAR (PolSAR), Hyperspectral...). Satellite imagery provides the coverage rate needed to identify and monitor human activities from agricultural practices (land use, crop types identification...) to defence-related surveillance (land/sea target detection and classification). By acquiring remotely sensed imagery over earth regions that land sensors cannot access, valuable information can be gathered for the defence against terrorism.

Developed on these themes the ASI's program was subdivided in ten half-day sessions devoted respectively to the following research areas:

• Target recognition/classification and tracking

• Sensor systems

• Image processing

• Remote sensing and remote control

• Belief functions theory

• Situation assessment

The lectures presented at the ASI proved to be of great contribution and importance to the research and development of the multisensor data fusion based surveillance systems used in rapid and robust situations and for threat assessment. The ASI gave all the participants the opportunity to interact and exchange valuable knowledge and work experience to overcome challenging issues in various research areas. This book summarizes the lectures that were given at this ASI.

An Advanced Research Workshop (ARW) related to this ASI was held in Tallinn, Estonia from June 27th to July 1st 2005. This ARW addressed the data fusion technologies for harbour protection. More information on this event can be found at http://www.canadiannatomeetings.com.

I would like to thank all the lecturers who accepted the invitation to participate in the ASI. The time they spent preparing their lectures and their active participation were key factors to the ASI's success. I would also like to thank them for the summary papers they provided to make this book happen. I extend my thanks to all the attendees of the ASI for their interest and participation.

A special acknowledgement goes to Kiril Alexiev, the co-director of this ASI who initiated this project and was always very supportive. His tremendous help in the coordination of all events and logistics was much appreciated. My warm thanks go to Gayane Malkhasyan and Masha Ryskin, my administrative assistants and interpreters who ensured that everything ran smoothly during the course of the ASI. I would also like to thank the officers from the Albena Congress centre office, in particular, Mrs. Galina Toteva for her extra assistance.

I would like to thank Pierre Valin and Erik Blasch who did the technical reviews of this book. Their judicious comments were very helpful. Very special thanks go to Kimberly Nash who reviewed the papers and formatted the book. Thank you for your patience and all the time you spent increasing the quality of the book.

Finally I wish to express my gratitude to NATO who supported this ASI along with Lockheed Martin Canada, the Institute of Parallel Processing of the Bulgarian Academy of Science, Defence Research and Development Canada, the European Office of Aerospace Research and Development of the USAF and the National Science Foundation, without whom it would have been impossible to organize this event.

Eric Lefebvre, Montreal, Canada