After days of silence, NASA’s Parker Solar Probe phones home

On Dec. 24, NASA’s Parker Solar Probe swooped closer than it ever had before to the sun, just a few million miles above its blazing hot surface.

The team behind the mission waited nervously, trusting that the probe would survive the encounter. Then, a few minutes shy of midnight Thursday, Parker phoned home.

The probe sent back not one but four signals indicating it was healthy, according to Nour Rawafi, an astrophysicist at Johns Hopkins Applied Physics Laboratory and the project scientist of the mission.

“It’s like the spacecraft wanted to reassure us,” he said, adding that the team was excited and relieved.

With the help of Venus’ gravity, Parker has crept closer and closer to the sun with a series of flybys since its launch in 2018. In the early stages of the mission, the team was anxious about the spacecraft getting so close to a star. But over time, Parker’s successful orbits — 21 and counting — built confidence.

Still, there was some fear that the probe might not survive this time. Parker’s heat shield is designed so that the front of the vehicle can withstand facing the blistering heat of the sun’s outer atmosphere, which reaches millions of degrees, while the back, which contains the probe’s sensitive instruments, sits at a comfortable 85 degrees Fahrenheit.

“Literally one side is at a temperature that is unfathomable,” said Joseph Westlake, the director of heliophysics at NASA. “And the back of it is a hot, sunny day.”

The spacecraft is also subject to a more tempestuous solar environment because the sun is currently at peak activity levels, which crest and trough on an 11-year cycle.

Parker’s latest flyby occurred at 6:53 a.m. Eastern time on Christmas Eve, grazing a mere 3.8 million miles above the solar surface while traveling at a whopping 430,000 mph.

But signs of the probe’s successful travels so far didn’t reach Earth until nearly three days later. Mission specialists crowded around a control room in Maryland on the night of Dec. 26 to wait for the expected signal, which, to their relief, arrived a few seconds early.

“I’m proud of what has been achieved,” Rawafi said. “It’s really a historic milestone for space exploration.”

The probe’s solar data collected from this flyby is expected to reach Earth on New Year’s Day. The data will help scientists study various aspects of the sun, including the origin of the solar wind, a stream of particles that creates a protective bubble around the solar system.

Parker’s data will also help scientists understand how the sun’s outer atmosphere, known as the corona, can be hundreds of times hotter than the solar surface below it.

“It’s like if you were standing next to a bonfire and you took a couple of steps back, and all of a sudden it got hotter,” Westlake said. “It just doesn’t make any sense.”

Parker isn’t done yet. It has two more solar flybys to accomplish at the same altitude as this one before the primary mission comes to an end in September.

But scientists are hopeful the mission will be extended a few more years, at least to close out the solar cycle. Parker launched when the sun was in a quiet phase, but by this past October NASA announced that the sun’s activity — flares and expulsions of plasma that brighten our skies with dancing lights — had officially reached a maximum. The next solar minimum is expected sometime during the 2030s.

In the meantime, the researchers look forward to seeing what surprises might come from the latest trove of solar data.

“That’s actually the thing we are waiting for — if there is anything new that we didn’t see before,” Rawafi said.

This article originally appeared in The New York Times.

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