Optics as a discipline is all about understanding and manipulating light (or more broadly electromagnetic radiation (from X-Rays through to far-Infra-red and sub-mm waves). We are all intimately familiar with our eyes as a vitally important imaging and sensor system (with our brain) that enables us to operate in a complex world. In a similar way spacecraft employ many different types of optical imaging and sensing systems (spectrometers) to observe and measure the Earth and the universe at large. Optical engineering is an essential capability to enable us to develop, build, test, fly and use optical instrumentation in space for the benefit of all. Think about weather satellites as a familiar example of how dependent we have become on the availability of reliable (optical) data from space.