The probe will fly through the sun's corona to gather data on the sun's great mysteries, such as the solar winds that create aurorae on Earth and disrupt satellites and power grids.
But if all goes according to plan, the probe will launch at 3:31 a.m. ET Sunday from Cape Canaveral, Florida, on a United Launch Alliance Delta IV Heavy rocket, one of the world's most powerful rockets. The agency is now targeting Sunday for the launch of the spacecraft which is created to go all the way to the Sun's atmosphere, or corona - closer to the Sun than any spacecraft in history.
- A last-minute technical problem has delayed NASA's unprecedented flight to the sun. Although the corona reaches millions of degrees, it's a wispy, tenuous, environment and so the spacecraft won't need to endure such severe temperatures.
United Launch Alliance, which made the rocket, will make a second attempt to launch the probe at 8.31am UK time on Sunday, although Nasa said that there was only a 60% chance of favourable weather conditions.
"Parker Solar Probe will carry four instrument suites created to study magnetic fields, plasma and energetic particles, and image the solar wind".
If the teams investigate the issues that delayed Saturday's launch and it can't be resolved in time for a 24-hour turnaround, the next attempt won't happen until Monday.
When it does launch, the Parker Solar Probe will get as close as 3.83 million miles to the sun's surface.
When it runs out of fuel, it will stay in the sun's orbit in perpetuity.
The probe will be controlled from the Mission Operations Centre based at the Johns Hopkins University Applied Physics Laboratory (JHU APL), which is where NASA handles its unmanned missions.
"With each orbit, we'll be seeing new regions of the Sun's atmosphere and learning things about stellar mechanics that we've wanted to explore for decades", Fox added.
The probe is protected by an ultra-powerful heat shield that is just 4.5 inches (11.43 centimeters) thick.
"It was just a matter of sitting out the deniers for four years until the Venus Mariner 2 spacecraft showed that, by golly, there was a solar wind", Parker said earlier this week.
The probe is equipped with a 4 1/2-inch thick carbon-carbon heat shield created to withstand temperatures of about 2,500 degrees Fahrenheit.
The project, with a $1.5 billion price tag, is the first major mission under Nasa's Living With a Star program.