Nour Rawafi of the Johns Hopkins Applied Physics Laboratory, which built and operates the spacecraft, discusses the Parker mission on March 15. (Marvin Joseph/The Washington Post)
NASA’s Parker Solar Probe has called home, sending a signal confirming that it survived a historically close encounter with the sun, when it traveled to within 3.8 million miles of the flaring surface of the star.
The probe “has transmitted a beacon tone back to Earth indicating it’s in good health and operating normally,” NASA reported early Friday.
The signal came just before midnight Thursday and ended several days of silence from the probe, which made its closest approach Tuesday - Christmas Eve - and was too close to the sun to maintain communication.
Traveling in the solar corona, the outermost layer of the sun’s atmosphere, the probe during its close encounter accelerated to 430,000 mph, faster than any spacecraft has ever flown.
“We sent something closer to the Sun than any other human-made object has ever gone - and it survived,” Nicola “Nicky” Fox, leader of NASA’s science mission directorate, said in an email Friday morning. “Now I have to be patient while we get the data downloaded and analyze it over the next few months to better understand our star and how it affects space weather.”
Gravity and the laws of orbital mechanics dictated the timeline of the flyby, and the spacecraft adhered to the schedule as predicted. The 1,510-pound Parker probe is in a highly elliptical orbit and has made a series of passes of the sun, each one closer than the last. NASA knew that shortly before 7 a.m. Tuesday, the spacecraft would make its closest pass.
What no one knew with absolute certainty was whether it would survive unharmed after enduring extreme temperatures. It appears to have done so. NASA said the probe will transmit detailed data from the flyby on Wednesday, New Year’s Day.
“Parker Solar Probe is braving one of the most extreme environments in our solar system,” said project scientist Nour Rawafi of the Johns Hopkins Applied Physics Laboratory, which built and operates the spacecraft. “This bold mission of exploration is bringing us closer than ever to unlocking the sun’s deepest mysteries.”
The Parker probe features a 4.5-inch-thick heat shield. The probe’s navigation system keeps the heat shield facing the sun at all times. On the sun-facing side of the heat shield, temperatures can reach 2,500 degrees, while the body of the spacecraft remains no warmer than 89 degrees, according to NASA.
The spacecraft, launched six years ago, carries a suite of instruments for studying the corona, where temperatures are 300 times greater than the sun’s surface. Astronomers can study the corona only during total eclipses, such as the one that North America experienced April 8.
This $1.4 billion NASA mission, however, is studying the corona the hard way and the hot way: flying directly into it. Precisely why the corona is so much hotter than the sun’s surface remains the subject of scientific scrutiny. The Parker probe will also study the origin of the solar wind and the processes that accelerate particles to near light speed. Earlier this year, Fox described the mission as “a voyage into the unknown.”
The Parker Solar Probe is named for Eugene Parker, a pioneering astrophysicist who in the 1950s overcame skepticism from colleagues to develop theories about the solar wind and the sun’s magnetic field, ideas later confirmed by spacecraft. He attended the Parker Solar Probe’s launch in 2018, and died in 2022 at age 94.
Counterintuitively, the laws of gravity make it hard to fly close to the sun. Objects orbiting the sun at a distance are moving at tremendous velocity (the Earth is booking along at roughly 67,000 mph), and to steer them close to the sun requires a technique to bleed off some of that speed. NASA did this by sending the Parker probe close to Venus many times. Each Venus flyby adjusted the probe’s orbit in a way that brought it closer to the sun with each solar flyby.
