Nasa’s unmanned Juno spacecraft on Monday began orbiting Jupiter, a key triumph for a $1.1 billion mission that aims to uncover the origins of the biggest planet in the solar system.
“Welcome to Jupiter,” said a commentator at mission control at Nasa’s Jet Propulsion Laboratory in Pasadena, California.
The room erupted in cheers as the solar observatory, which has travelled 2.7 billion kilometers since it launched five years ago from Cape Canaveral, Florida, successfully entered its aimed-for orbit around Jupiter at 11:53 pm (0923 IST Tuesday).
Scott Bolton, Juno principal investigator from the Southwest Research Institute in San Antonio, Texas admitted to being “nervous” and “scared” about the fate of the spacecraft, which is travelling at a speed of more than 130,000 miles per hour (209,200 kilometers per hour) toward what he called “the king of the solar system.”
A key concern is that the spacecraft must survive radiation levels as high as one hundred million X-rays in the course of a year, explained Heidi Becker, senior engineer on radiation effects at Nasa’s Jet Propulsion Laboratory.
Those high-energy electrons, moving at the speed of light, “will go right through a spacecraft and strip the atoms apart inside your electronics and fry your brain if you don’t do anything about it,” she said.
“So we did a lot about it,” she added, describing the half-inch-thick layer of titanium that protects the electronics in a vault to bring the radiation dose down.
Still, she described the close approach as going “into the scariest part of the scariest place... part of Jupiter’s radiation environment where nobody has ever been.”
Juno must also avoid debris as it speeds through a belt of dust and meteorites surrounding Jupiter.
“If it gets hit -- even by a big piece of dust, even by a small piece of dust -- it can do very serious damage,” Bolton said.
On approach, the engine doors are open, leaving the nozzle vulnerable, he said.
“If any dust is in our way and hits that nozzle, it will knock a hole right through the coating that protects that nozzle and allows the engine to burn uninterrupted,” he told reporters.
“That is one of the big gambles.”
After that, a tricky, fully automated orbit maneuver must go well as the engine fires to slow it down enough to be captured by Jupiter’s orbit.
The spacecraft must then re-orient itself toward the Sun in order to power the solar arrays.
If it fails to enter orbit, Juno may shoot past Jupiter, bringing a mission 15 years in the making to a swift end some 540 million miles (869 million kilometers) from Earth.
How Jupiter formed
Scientists hope to find out more about how much water Jupiter holds and the makeup of its core in order to figure out how the planet -- and others in the neighbourhood, including Earth -- formed billions of years ago.
The solar system’s most massive planet is fifth from the sun.
With an atmosphere of hydrogen and helium, it’s known for its Great Red Spot, a storm bigger than Earth that has been raging for hundreds of years.
The first mission designed to see beneath Jupiter’s clouds, Juno is named after the Roman goddess who was the wife of Jupiter, the god of the sky in ancient mythology.
She was said to be able to see through the clouds with which Jupiter veiled himself to hide his mischief.
The Nasa mission aims to orbit Jupiter from pole to pole, sampling its charged particles and magnetic fields for the first time and revealing more about the auroras in ultraviolet light that can be seen around the planet’s polar regions.
Juno should circle the planet 37 times before finally making a death plunge in 2018, to prevent the spacecraft from causing damage to any of Jupiter’s icy moons, which Nasa hopes to explore one day for signs of life.
Although Juno will not be the first spacecraft to circle Jupiter, Nasa says its orbit will bring it closer than its predecessor, Galileo, which launched in 1989.
That spacecraft found evidence of subsurface saltwater on Jupiter’s moons Europa, Ganymede and Callisto before making a final plunge into Jupiter in 2003.
Nasa says Juno should be able to get closer than Galileo -- this time within 3,100 miles (5,000 kilometers) above the cloud tops.
“We have done everything humanly possible to make this mission a success,” said Nasa’s director of planetary science, Jim Green.
However, “it is still a cliffhanger for me, too.”