Solar Orbiter

Solar Orbiter is an ESA-led spacecraft with strong NASA participation, launched in February 2020 to connect observations of the Sun with measurements of the solar wind. Its heliocentric orbit and gravity assists allow observations from different distances and increasing solar latitudes, rather than restricting every view to the plane from which Earth sees the Sun.^[ref]

Its ten instruments divide into six for remote sensing and four for sampling the surrounding environment. The remote sensing instruments observe emitted or scattered light from the Sun and its surroundings. The local instruments measure plasma, energetic particles, electric fields, magnetic fields and waves. A magnetometer and particle analysers therefore answer different questions from an image: one measures conditions at the spacecraft, while the other helps locate the remote source.^[ref]

A scientific comparison can ask whether a feature observed near the Sun is associated with a later change in the velocity distribution or composition of locally sampled particles. Identifying the connection requires accounting for the material's travel time and the changing geometry; simultaneous timestamps alone do not establish a common origin. The mission's combined apparatus makes such tests possible. A 2024 analysis, for example, separated proton and alpha particle populations in its solar wind data rather than representing all ions by one mean speed.^[ref]