Mechanical design of EUI.
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The Extreme Ultraviolet Imager (EUI) is a suite for optical imaging designed for the Solar Orbiter spacecraft. Solar Orbiter will be lauched in 2017 and its nominal mission lasts until 2024 (with the possiblity of an extended mission until 2026). This means that the imagers will be able to monitor the Sun activity in a period which covers the transition from the maximum to the minimum of the 11 year solar cycle. Along the orbit, the spacecraft will approach the Sun as close at 0.30 AU at perihelion, while the maximum aphelion is located at about 0.95 AU. Further more, about 3 years after the launch, the spacecraft will begin an out-of ecliptic phase, with an inclination which increases toward the maximum value of about 30º with respect to the equatorial plane.
The suite is composed of 1 Full Solar Imager (FSI) and 2 High Resolution Imagers (HRI).

Bandpass 174 Å 174 Å
1216 Å 304 Å
  (filter switch)
FOV 0.28 arcdeg 3.8 arcdeg
(⇔ 15% Sun ∅) (⇔ 2 Sun ∅)
Resolution 1 arcsec 9 arcsec
(⇔ 200 km) (⇔ 12800 km)
Cadence ≥ 1 s 600 s
≤ 1 s

Main EUI features (the FOV and the resolution in distance are computed assuming a perihelion and aphelion of 0.30 and 0.95 AU).

The FSI continuosly monitors the full Sun in two bandpasses (a hot and a cold channel), with a spatial resolution and a cadence able to capture the majority of the phenomena occurring on both global scales (such as EIT and MORETON waves) and local scales (such as jets at coronal hole boundaries or CME launching).

The two HRIs, on the contrary, have a limited field of view in favour of a higher cadence and an increased spatial resolution. They will be operating only during the closest approaches to the Sun and in limited, well-defined observing periods. Their bandpasses have been selected in order to monitor a region at three different temperatures (typical emission lines of the chormosphere, transition region and low corona are chosen), which allows to establish the spatial and temporal connection of the observed structures as they develop in the different layers of the atmosphere.