NASA's Parker Solar Probe is scheduled to make its closest approach yet to the Sun, approximately 3.8 million miles from the star's surface, on Christmas Eve.
"No human-made object has ever passed this close to a star, so Parker will truly be returning data from uncharted territory," said Nick Pinkine, Parker Solar Probe mission operations manager at the Johns Hopkins Applied Physics Laboratory (APL).
In addition to traveling far closer to the Sun than any previous mission, the spacecraft will also be barreling along at approximately 430,000 miles per hour.
The spacecraft was launched on August 12, 2018, and is designed to study the workings of the Sun, specifically how solar corona and wind function. To do this, it must come closer to the star than any other mission, make its observations, and transmit them back to Earth over subsequent weeks. Scientists expect to receive a beacon tone on December 27 to confirm that it survived the flyby.
The spacecraft has a 73 kg heat shield, measuring 11.4 centimeters thick with a diameter of 2.5 meters. Scientists reckon that the Sun-facing side of the carbon-composite shield will experience temperatures of about 1,000°C (1,832°F) during its flyby, but the instruments in the shield's shadow should remain at a more comfortable 29°C (84°F). The heat shield is designed to withstand temperatures as high as 1,377°C (2,511°F).
The probe is well within the orbit of Mercury and has been using gravity assist flybys of Venus to tweak its trajectory. The trajectory design called for 24 orbits of the Sun and seven gravity assist flybys of Venus, the last of which took place on November 6.
December 24 represents the mission's closest approach to the Sun, and two more approaches are planned in 2025. After that, the primary mission will be complete and, according to APL, "the team will decide whether to keep the spacecraft in that orbit or reposition it."
The Parker Solar Probe was named for Eugene Parker in 2017. Parker was then the S. Chandrasekhar Distinguished Service Professor Emeritus at the University of Chicago and had proposed concepts explaining how stars, such as the Sun, give off energy via solar wind and why the Sun's superheated atmosphere - the corona - is hotter than the surface of the Sun itself.
It was the first time NASA named a mission for a living person. Parker died in 2022 at the age of 94. ®