The Extreme Ultraviolet Imager (EUI) is part of the remote sensing instrument package of the ESA/NASA Solar Orbiter mission that will explore the inner heliosphere and observe the Sun from vantage points close to the Sun and out-of-the-ecliptic. Solar Orbiter will advance the ’connection science’ between solar activity and the heliosphere.

EUI aims at improving scientific understanding of the structure and dynamics of the solar atmosphere, globally as well as at high resolution, and from high solar latitude perspectives.

EUI consists of 3 telescopes that are optimized to image in Lyman-α and EUV (17.4 nm, 30.4 nm) to provide a coverage from chromosphere up to corona. EUI is designed to cope with the strong constraints imposed by the Solar Orbiter mission characteristics. Limited telemetry availability is compensated by state-of-the-art image compression, on board image processing and event selection. The imposed power limitations and potentially harsh radiation environment lead to the usage of novel CMOS sensors. As
the unobstructed field of view of the telescopes needs to protrude through the spacecraft heat shield, the apertures have been kept as small as possible, without compromising optical performance. This led to a systematic effort to optimize the throughput of every optical element and the reduction of noise levels in the sensor.

EUI will bring unique science opportunities thanks to its specific design, its viewpoint and thanks to the planned synergies with the other Solar Orbiter instruments.