We have explored outer space including our moon, other planets and even the edge of the solar system but not the Sun. The Parker Solar Probe (PSP) is revolutionizing solar exploration. The spacecraft will fly within 6 million km from the solar surface which is close enough to melt steel (for reference the average distance between Sun and Earth is about 149 million km). PSP will be the first ever man-made object to approach so close to a star.
The mission has a launch window between 31 July – 19 August 2018. The spacecraft will do 7 flybys of Venus, using gravity assist to accelerate itself to make its first close approach to the Sun by 2024. Nevertheless, first light will be achieved within 3 months of its launch. The mission includes 24 orbits around the Sun with the final 3 orbits having the closest approach to the Sun. Eventually it will plunge into the Sun.
A mission to the Sun was first proposed in 1958 but technical challenges took 6 decades to overcome. To protect the instruments from the Sun’s intense heat, a special heat shield made of carbon graphite sheet affixed to carbon foam blocks was specifically designed. It is a 11.5 cm thick shield which can withstand temperatures of up to 1400°C, keeping the instruments inside at room temperature. The solar panels powering the spacecraft, however, are outside the heat protectors. At closest approach the panels will receive 25 times the energy as it would have in Earth orbit. They are therefore fitted with an innovative cooling system to maintain their temperature at 160°C.
The many hidden secrets of the Sun have not been revealed from remote observations. It is therefore essential to get up close and personal with the Sun. The solar corona is very dynamic, producing flares and coronal mass ejections. Observing these phenomena closely will help in understanding their origin and how they accelerate energetic particles. Acceleration of the solar wind is yet another unanswered question. Keys to understanding the heliosphere and the magnetosphere lie in understanding these solar phenomena. All these phenomena directly impact life on Earth like satellite communications, power grid issues, pipeline erosion, radiation exposure on flights, astronaut safety to name a few. The PSP will improve our knowledge of Sun-Earth connections thus enabling better predictions of space weather.
During each orbit there will be a 11-day period when communication with the spacecraft will be lost due to high radio noise from the Sun. PSP will hibernate during this period. Overcoming these radio quiet periods will be one of the biggest challenges of this mission. Several space missions have been jeopardized due to lack of communication. Scientists have programmed autonomous recovery of the spacecraft failing which the spacecraft must enter safe mode and wait to be reactivated from Earth.
PSP is the first spacecraft to be named after a living person. Prof. Eugene Parker was the first to hypothesize the presence of the solar wind which was later proven to exist by multiple observations. His works are fundamental to the study of how stars interact with the worlds around them. He also proposed explanations for the super-hot corona which are still under investigation. Since the mission objectives are very similar to his work it was only right to name the mission in honor of his body of scientific work.