The corona, the outermost region of our Sun’s atmosphere, exhibits two remarkable features:
- Temperatures there reach 1 million degrees centigrade, more than 100 times hotter than at the Sun’s surface (where it doesn’t exceed 6,000°C).
- It is the source of the solar wind, a stream of ions and electrons ejected at high speed into interplanetary space. This stream bombards the planets of the solar system and can even cause disruptions on Earth, despite its protective magnetic sheath.
Since discovering the solar corona in the 1940s, scientists have learned a great deal more about the solar wind and the Sun itself, but they still don’t understand the mechanisms going on inside the corona. Only in-situ measurements will give them the keys to these underlying physical processes.
Parker Solar Probe aims to study the solar corona, which extends for several million kilometres out from the Sun. The spacecraft will observe the Sun up close, passing several times within a few million kilometres from its surface.
The mission’s goals are to:
- Determine the structure and evolution of the magnetic fields that generate both slow- and fast-moving particles in the solar wind
- Trace how energy and heat move through the solar corona and accelerate the solar wind
- Determine the processes accelerating and transporting energetic particles
- Study the phenomenon of "dusty plasma" in the region of the Sun and how it impacts the solar wind and formation of energetic particles
The spacecraft will be sent aloft by an Atlas 551 launcher topped by a modified Star48 solid propellant booster stage to impart an Earth escape velocity of 12.6 km/s. It will use 7 gravity assists from Venus to gradually reduce the perihelion of its orbit, passing at least three times within six million kilometres of the Sun. It will pass close for the first time six years after launch, in 2024. The next two passes are expected to be made within a year. The period of the final orbit will be 88 days, identical to that of Mercury. The spacecraft has a special carbon shield to protect it from the Sun’s heat.