Remote sensing instruments work like a camera or our eyes; they detect light waves coming from the Sun at different wavelengths. As light travels at 300 000 km/s, it takes 2.5 minutes to reach Solar Orbiter’s instruments at closest approach.

Meanwhile, Parker Solar Probe’s in situ instruments work more like our nose or tastebuds. They directly ‘taste’ the particles and fields in the immediate vicinity of the spacecraft. In this case, Parker Solar Probe will measure solar wind particles that travel away from the Sun at speeds of more than a million kilometres per hour. Though this seems very fast, it is more than 500 times slower than the speed of light.

“In principle, Solar Orbiter alone can use both methods,” points out Andrei Zhukov from the Royal Observatory of Belgium, who is working on the joint observations. “However, Parker Solar Probe comes much closer to the Sun, so can directly measure the properties of the solar wind – like its density and temperature – closer to its birthplace, before these properties change on its journey away from the Sun.”