NASA’s Juno spacecraft put itself into a temporary shutdown at 10:47 p.m. US Pacific Daylight time on October 18 as it approached a fly-by of Jupiter. It was the mission's second glitch in a week, following a problem with its propellant system.
Juno remains safe and is looping around Jupiter on a 53.5-day elliptical orbit. But the spacecraft did not gather scientific data as it whizzed 5,000 kilometres above the giant planet’s cloudtops on this, its second close pass since arriving at Jupiter on July 4.
“We’ll just hang out for a couple of days while we figure out what went wrong,” says Scott Bolton, a planetary scientist at the Southwest Research Institute in San Antonio, Texas, and the mission’s principal investigator.
Juno slipped into “safe mode”, possibly in response to an onboard computer reboot, a little over 13 hours from its closest approach to Jupiter. The mission has been in safe mode several times since its 2011 launch; operations are typically restored within hours to days. Engineers are working through a series of steps to restore communications. If and when they start talking to Juno again, they will turn towards resolving a separate, apparently unrelated propellant issue.
On October 14, NASA announced that Juno would delay burning its engines as it had planned to during the October 19 close fly-by, or perijove. The engine burn would have nudged the craft from its 53.5-day orbit to a 14-day orbit. But two helium valves needed for the procedure did not respond as expected while being pressurized in the lead-up to the burn. Mission managers decided to put it off, hastily scheduled a series of science observations for the upcoming perijove—and then, four days later, saw their spacecraft enter safe mode.
Juno can stay in its 53.5-day orbit indefinitely and still get nearly all of the science it had been planning to gather at Jupiter, Bolton says, including unraveling the mysteries of the planet's origin and whether or not it has a core. The science discoveries come mostly at each close fly-by, so stretching out the time between each perijove means that researchers gather data more slowly.
An early look
Despite Juno's current issues, there was a spot of good news. Bolton presented early results from Juno’s first flyby of Jupiter—on August 27—at a joint meeting of the American Astronomical Society’s Division for Planetary Sciences and the European Planetary Science Congress. The data included one of the best looks yet deep into Jupiter’s swirling clouds.
A microwave instrument on Juno has found that Jupiter’s wide atmospheric bands extend as much as 400 kilometres deep into the gas giant—though the bands display new twists and turns the deeper they go. “Deep down Jupiter is similar but also very different from what we see on the surface,” Bolton says.
Juno’s camera has also captured new visual details on the storms, like the famous Great Red Spot, that rage across Jupiter. Unlike other spacecraft that have visited the giant planet, Juno is whizzing up and over the planet’s poles, giving researchers the first-ever view of the northern and southern extremes. The spacecraft's first fly-by found that Jupiter’s north pole lacks the mysterious hexagon of swirling clouds that dominate Saturn's north pole.
Another new image shows a towering cyclone, its clouds illuminated from the side as the sun rises on Jupiter. At 7,000 kilometres across and 100 kilometres tall, “it is a truly towering beast of a storm,” Bolton says.
Other data, not yet made public, includes information on Jupiter’s powerful magnetic and gravity fields, as well as its shimmering auroras. “Every dataset has a discovery aspect in it that we’re in the middle of trying to understand,” says Bolton.
The next fly-by is scheduled for December 11.
This article is reproduced with permission and was first published on October 20, 2016.