We would like to welcome you to this year’s Electro-Optical and Infrared Systems: Technology and Applications XVII Conference which was originally due to take place in Edinburgh, UK. However, the Covid-19 pandemic, as well as affecting the lives and activities of many people, has made it necessary to replace our 2020 Conference with an online event. For many scientists and engineers, attending a conference is not just about hearing presentations on the latest research and development work. The chance to catch up with our peers and make new contacts over a coffee between the presentations is almost, if not, as equally important. The importance of such ‘in-the-margins’ conversations is well recognised by SPIE, and they have made enormous efforts to maximise opportunities for virtual discussions instead. However, the absence of the informal networking and interaction remains a loss to many of us, and we hope that normality returns for future conferences. The impact of the pandemic has wrong-footed many experts and politicians in terms of both its scale and dynamics. Within this turmoil, our conference organisers have been faced with the enormous challenge of trying to plan an international meeting, and we suspect that many of us are not fully aware of the pressure and frustration that they have faced. To the knowledge of these Conference Chairs, there have been at least three incarnations of the Conference: a four-day event, a three-day event, and finally the online event. We therefore believe that it is important to acknowledge here the efforts of the SPIE staff members who not only worked tirelessly to enable the Edinburgh conference to go ahead, but adjusting swiftly to the online format when events moved against us. On a more personal note, we are pleased to announce that SPIE has honoured Dr Dave Huckridge by appointing him as a SPIE Fellow. Many of you will know Dave Huckridge who was our Conference Chair for the first fifteen years of its existence and who did so much to grow the event in terms of both the number of attendees and the quality of the presentations. It was planned to present him with his award in Edinburgh, but regrettably this became impossible when the decision to go online was made. Nonetheless, we would like to thank Dave Huckridge for his contributions to our community over many years. We would also like to thank David Titterton, Roger Appleby, and Keith Lewis for sponsoring the application within SPIE. Our Conference is a very important part of our community and it provides a forum for the exchange of innovative thoughts and development across a spectrum that ranges from basic research through to system designs and applications. Few other international events offer such breadth and depth for the defence and security sector, and this is reflected through its ongoing popularity with both academia and industry. Many of our authors have faced not only the uncertainty of travel but also restrictions by their funding organisations. To those who were unable to submit their work this year, we thank you anyway, and hope that you will consider returning to our Conference next year. However, and despite these uncertainties, we have been pleased with the number of authors who have been able to contribute papers, as well as acknowledging the quality of their research and development work. Despite the problems that we have all faced, it is an encouraging sign to see that the creation of new ideas and sensor concepts has not stopped. The Electro-Optical and Infrared Systems: Technology and Applications Conference provides a forum for researchers and designers to present their latest work, and for all of us to gain an insight into how such developments can meet the needs of current and future sensor-based systems and their applications. Having an applications-focus is invaluable: it offers a means of interpreting and analysing technology in a real-world context where benefits can be readily understood in terms of both capability and implementation potential. The Conference also brings together technologists, designers, systems engineers, and end-users: the essential stakeholders needed to take ideas and technology forward. We have retained the same overall structure for the Conference as last year, with principal sessions on Sensors and Technology, Systems and Applications, Image and Data Processing, and Modelling and Simulation. This is a broad technology canvass, but it is one that is needed to provide the framework required to understand sensor technology and their interfaces from a system perspective. Distributed across these topics, we have received approximately 30 contributions which offer new insights and ideas into detectors and camera technology, sensor system concepts and their applications, the exploitation of scene information and its extraction, and new approaches for modelling and simulation at both components and system levels. Whilst we may not be able to meet in person this year, our community has shown a strong resilience and collective spirit for maintaining open dialogue and the free exchange of ideas. We therefore conclude by once again thanking our authors for their contributions and hoping that the online participants find the papers of interest and beneficial to their own ongoing research and development work.