Europa, Ganymede, Callisto, meet your new companion: Juno.
After a five-year, 1.7-billion-mile journey, the Juno spacecraft entered into its target orbit around Jupiter yesterday at 11:53 pm Eastern time. It arrived almost exactly on schedule, within one second of what mission control had been predicted.
“NASA did it again,” said Scott Bolton, the scientist in charge of the Juno project, in a news conference afterward at the California Institute of Technology’s Jet Propulsion Laboratory, where the mission is being directed.
To slow itself down enough to be captured by Jupiter’s gravity and pulled into its orbit, the spacecraft began firing its main engine continuously 35 minutes before it reached the orbital zone, decelerating by 1,212 mph.
Juno’s adventures took it through hazardous belts of radiation to within 2,000 miles of Jupiter’s cloud tops before heading outward again, away from the planet. Once away, the probe pivoted so its solar panels were facing the sun.
The spacecraft’s instruments were turned off during the initial orbit entry to protect them from radiation, but they will be turned on again in two days time. At the moment, the probe is on a 53-day orbit cycle, but it will shift to a 14-day orbit on October 19, enough to complete 37 trips around Jupiter over the next 20 months. Juno’s two-week orbital period was chosen to minimize the instrument’s exposure to damaging radiation from the intense belts that surround the planet.
This is only the second time a man-made spacecraft has reached Jupiter to orbit the planet. In 1995, NASA’s Galileo probe reached Jupiter and spent eight years surveying the planet as well as its moons. However, Galileo did not possess the complex equipment that Juno has on board, which will be used to study the planet’s composition and evolution. Galileo also spent the majority of its orbit more than five times further away from Jupiter, so it was not able to gather as much information.
“We have a chance with Juno to go back and study the planet in its own right,” James L. Green, the director of planetary science at NASA, said during a news conference earlier on Monday.
Scientists believe that Jupiter was the first planet to form, which means it could hold clues about evolution of the rest of our solar system. Studying things like how much water Jupiter contains and the possible presence of a rocky core could reveal where in the solar system Jupiter was originally created.
To study these factors, Juno contains instruments that measure the magnetic and gravitational fields of Jupiter, and the microwaves flowing from within the planet.
Eventually, the exposure of radiation as the probe flies past Jupiter will take a toll of the equipment onboard the spacecraft. On February 20, 2018, during its 37th orbit, Juno will take a final plunge into Jupiter’s surface, in the same way that Galileo was disposed of in 2003. This destructive conclusion will ensure that Juno doesn’t crash into Europa, which is a possible candidate for life in our solar system.