= Solar Orbiter
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<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.<Solar Orbiter factsheet by ESA>[Mission, Partnerships and Journey]{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.<Solar Orbiter Mission by the US Naval Research Laboratory>[instrument division and lists; physical connectivity between Sun and solar wind]{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.<Comparative study of the kinetic properties of proton and alpha beams in the Alfvénic wind observed by SWA-PAS onboard Solar Orbiter by Roberto Bruno and others>[abstract, SWA-PAS measurements and population separation]{ref}
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