After a nearly five-year journey, NASA's solar-powered Juno spacecraft arrives at Jupiter Monday. But for the mission to succeed, Juno will need to navigate a tricky maneuver — including slowing by around 1,212 mph — so it can be inserted into orbit in what NASA calls "the king of our solar system."
As of noon Monday, the mission was down to one last Jupiter rotation — 10 hours, here on Earth — before Juno reaches orbit distance. To follow the spacecraft's progress, you can watch NASA TV coverage of the orbital insertion tonight, starting at 10:30 p.m. ET.
"It's a milestone for planetary science," NASA Director of Planetary Science Jim Green said at a midday news conference, adding that the Juno mission should provide far more data than has been gleaned from fly-by trips past the gas giant.
As of noon Monday, Juno was an hour away from passing Jupiter's second-closest moon, Europa, with only Io remaining to pass, Juno Principal Investigator Scott Bolton said. He added, "It's getting very real."
Bolton went on to discuss what he called "the true hazard" of Jupiter — its massively powerful radiation belts that send electrons, protons and ions whizzing around the planet at nearly the speed of light. Those particles could wreak havoc with Juno's electronics.
As he described the difficulty of getting a spacecraft through that radiation, Bolton also noted Jupiter's ring of debris that could present real problems to Juno's engine — which will need to have its nozzle open and pointed toward the planet to take speed off of the craft.
In a maneuver that will begin tonight, Juno will approach Jupiter from high over the planet's north pole, said Rick Nybakken, Juno's project manager from NASA's Jet Propulsion Laboratory in Pasadena, Calif. The craft will then slide along the planet's surface, fire its main engine to brake, and alter its own rotation and placement so that its solar array is pointed toward the sun.
There's a 48-minute time delay for communication with the spacecraft, which means NASA won't start to learn the effects of the 35-minute engine burn for some 13 minutes after the burn completes.
NPR's Joe Palca reports that if the orbit insertion goes smoothly, "Juno will provide a lot answers to questions about Jupiter. Although it's well-known that the gas giant is made up primarily of hydrogen and helium gas, the planet's core remains mysterious."
Juno has a hexagonal body — measuring 11.5 feet in diameter — that projects three solar arrays that each measure 29.5 feet by 8.7 feet. Bolton says the spacecraft's 60 square meters (more than 650 square feet) of solar arrays produce 500 watts of power.
NASA plans for Juno to orbit Jupiter 37 times over the next 20 months as it provides new information about the gas giant's core and composition.