The Solar Orbiter (SolO) is a Sun-observing probe developed by the European Space Agency (ESA) with a NASA contribution. Solar Orbiter, designed to obtain detailed measurements of the inner heliosphere and the nascent solar wind, also performs close observations of the polar regions of the Sun which is difficult to do from Earth. These observations are important in investigating how the Sun creates and controls its heliosphere. Solar Orbiter makes observations of the Sun from an eccentric orbit moving as close as ≈60 solar radii (RS), or 0.284 astronomical units (au), placing it inside Mercury's perihelion of 0.3075 au. During the mission the orbital inclination will be raised to about 24°.

Wikipedia: https://en.wikipedia.org/wiki/Solar_Orbiter. Related NASA reference: https://science.nasa.gov/mission/solar-orbiter/. Description adapted from Wikipedia contributors (CC BY-SA 4.0; https://creativecommons.org/licenses/by-sa/4.0/).