Scientists are putting the finishing touches on the Parker Solar Probe ahead of its mission to fly directly into the Sun's atmosphere.

The spacecraft will have to survive temperatures as high as 1,371 degrees Celsius, impacts by supersonic particles and powerful radiation as it circles as close as 7 million kilometres to the Sun.

Data sent back to Earth 140 million km away will help scientists figure out why the Sun's atmosphere, its corona, is hotter than its surface.

But Parker Solar Probe's deputy project scientist believes it could also lead to unanticipated discoveries.

"I'm almost certain that we will learn about new phenomenon that we know nothing about now," Nour Raouafi said.

"That is really super, super exciting for us."

The spacecraft will be shipped to Cape Canaveral in Florida ahead of take-off in July.

"From there, she has a couple of months of just sort of final testing … and the next stop is space," explained project scientist Nicky Fox of the Johns Hopkins University Applied Physics Lab.

The space probe will use Venus to help control its trajectory and speed. ( Supplied: NASA )

The spacecraft, designed and built by the university, will fly around Venus seven times to get itself into orbit around the Sun in December 2024.

NASA is paying about $1.5 billion to build and launch the spacecraft.

The probe is expected to orbit the Sun 24 times, edging closer on each pass.

The size of a small car, it will be outfitted with five science instruments to measure and sample the Sun's corona.

In addition to expanding knowledge of stellar physics, the information is expected to help engineers design better instruments and techniques for predicting solar storms and other events that can cripple satellites, disrupt power grids and affect aircraft travel on Earth.

The mission has been a dream of scientists for decades but nascent technologies now make it possible, explained NASA astrophysicist Nicholeen Viall.

"They have this carbon composite heat shield that protects all of the instruments on the backside," she said.

"There is one instrument that peaks out and does measure directly the solar corona — the atmosphere of the Sun."

The probe is expected to orbit the sun 24 times, edging closer on each pass. ( Supplied: Johns Hopkins University Applied Physics Laboratory )

While scientists are excited for the scheduled July 31 launch, they also admit to feeling stressed.

"Every time we get closer to the Sun, there is a period of time where we cannot communicate with the spacecraft," Mr Raouafi.

"It has to be autonomous. It has to depend on itself, so for several days we cannot do anything to it."

He said he would be waiting for the call from space: "I am Parker Solar Probe and I am doing great".

Reuters