It's been more than a decade since an American spacecraft passed Venus with the Mercury-bound Messenger probe
The Parker Solar Probe will pass the intensely cloudy planet Wednesday. It’s one of seven flybys by the probe on its way to the real scientific goal: our sun.
This week’s Venus flyby allows for historic first perihelion, or close approach to the sun, Nov. 5. Parker will then become the closest probe to ever orbit the sun, passing within 35 solar radii. NASA’s Helios-B previously held the record at 100 radii. One solar radius is about 432,000 miles.
“The whole idea of the mission is to go as close to the sun as possible,” said Mihir Desai, a scientist at Southwest Research Institute and co-investigator on one of Parker’s instruments.
This first pass is not about the science, however, as much as it is about safely executing the orbit.
"We have to get everything right first,” Desai said. “There is always a tussle between scientists and the spacecraft mission management. The scientists want data all the time and the mission managers say, ‘No, look, we need to get you into the right orbit with the right location and everything is orienting correctly so that we don't damage our instruments.’ ”
Desai’s research focuses on the radiation types that are most dangerous to electrical and communications infrastructure, how these types of radiation reach Earth, and how they can predict them better.
One such event is known as a coronal mass ejection, which are large, frequent eruptions of plasma. The eruptions are so violent, they can sometimes impact Earth. One of the largest eruptions was recorded Sept. 1, 1859, throwing the world’s telegraph system into disarray, overloading circuits, and shocking operators.
Now, scientists say the world is even more vulnerable due to our reliance on GPS, mobile phones, and electrical grids. Despite 150 years passing, scientists still aren’t able to predict these violent incidents well.
“By the time it gets to us, it’s all mixed up,” said Desai of the particles. “Scientists don’t know exactly how these particles get accelerated and how they reach Earth. That was one of the prime reasons we wanted to go as close as possible to the acceleration regions.”
To get the data they want, Desai said Parker will need to get to within 10 solar radii, or around 4.3 million miles, from the surface of the sun. Getting there will take 55 times more energy than traveling to Mars, according to NASA. And it is the reason for the elaborate orbit pattern that includes seven Venus flybys and 24 solar orbits.
Desai’s instrument is part of the Integrated Science Investigation of the Sun, which will use two sensors to measure energy particles. It is one of several instruments scientists are hoping will help better predict solar flares and CMEs, which occur about every 11 years, but that isn’t guaranteed.
“We will be seeing an active solar period,” Desai said.
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When a flare occurs, the hope is Parker is not in perihelion, because it could be lost, but he said they aren’t confident it won’t happen at an inopportune time.
”If we could predict that we wouldn’t be flying a mission like this.”
Other science missions include discovering how the corona receives energy from its surface, measuring how the magnetic field changes over time, and how solar wind works.
All systems have been tested. The ship sent out its “first light” data in mid-September. Last week, the probe reoriented itself so its powerful heatshield faced the sun.