The long wait is almost over as NASA's Juno Spacecraft is only four days away from the biggest planet in the Solar System, Jupiter.

Juno, launched in 2011, traveled for five years to reach the "biggest and baddest" planet in the Solar System. Due to the harsh environment of Jupiter, the solar-powered spacecraft will have to survive torrential radiation emitted by the planet to complete its mission.

NASA's Juno mission aims to probe the structure, composition and evolution of the giant gas planet. "Jupiter is the planet on steroids in our solar system; everything about it is extreme," Juno principal investigator Scott Bolton, said in an interview with Space.com. "It's a big challenge, but we have to take those challenges if we're going to explore and learn about ourselves, and how we fit into nature," Bolton added.

Upon successfully entering Jupiter's orbit, Juno will proceed to perform its integral mission that includes measuring the water content of the planet. This will help scientists understand the water content of not just the planet but also in the Solar System. 

Another major task entrusted to Juno and the equipment aboard the spacecraft is to scrutinize and understand the composition of the planet. Believed to be as old as the sun, understanding Jupiter's composition will give light to the planet-forming years of the Solar System. It is also important to prove whether or not Jupiter also has a rocky and solid core.

The journey was welcomed with anticipation especially on June 21 when Juno beamed back an image of its destination planet including four of its moons, heightening the excitement of scientists and the public awaiting Juno's arrival on Jupiter. The image was captured from a distance of 6.8 million miles (10.9 million km).

But the anticipation and excitement are also shrouded with a little bit of fear, as Juno will have to survive a difficult maneuver to enter Jupiter's orbit. An expert says that both the practice of entry on-orbit and landing maneuvers proved to be difficult on their own way.

"One is bizarrely difficult and the other is incredibly difficult," Art Chmielewski, U.S. project manager for Rosetta mission said in an interview with Phys.Org. That is why NASA's Jet Propulsion Laboratory are making sure that Juno will survive.

To follow up on Juno's itinerary, take note that the on July 4, 8:18 pm Pacific time, Juno will burn its engine to enter the orbit in a difficult breaking maneuver. At exactly 35 minutes after, NASA should receive a transmission, using a simple communication broadcast system, that the spacecraft successfully entered orbit and it'll mark the start of the exploratory science mission.