Traveling at 165,000 mph toward a swirling gas giant Monday night, the Juno spacecraft wouldn’t get a second chance. If its Leros 1b engine had burned too long, Jupiter would have swallowed Juno in its gaseous maw. If the British-made engine burned too short, the spacecraft would have zipped further into space, lost forever in the inky darkness. But Juno didn’t need a second chance late into the night of July 4, as its hardened little engine fired for a total of 2,102 seconds, perfect to within a second, and neatly launched the spacecraft into orbit around Jupiter.
Back on Earth engineers from the Jet Propulsion Laboratory in California gave a warm cheer. For the past five years, a team of 300 engineers has guided Juno on its path. Another 900 built and launched the spacecraft. Moments after the orbital insertion, Scott Bolton, the mission’s principal investigator, saluted the team of engineers and told them they were the “best ever.” In his euphoria, Bolton added, “You’ve just done the hardest thing NASA has ever done.”
Maybe not, but it’s no small feat to spend the better part of a decade building a spacecraft to survive Jupiter’s harsh radiation, launch it 1.7 billion miles in five years, and then dropping exactly where you want around a planet 2.5 times as massive as all the other planets in the solar system – combined. At the end of the day, Juno hit a keyhole several tens of kilometers wide.
In reality, NASA has now also sentenced its $1.1 billion (~£850 million) spacecraft to death. Mission managers hope to get 37 orbits around Juno in the next 20 months before radiation slowly breaks down its electronics and propulsion system. While a 1cm-thick wall of titanium encases the spacecraft’s electronics to provide some protection, some of the nine instruments could begin to fail in as few as eight or 10 orbits. Before the spacecraft fails completely, engineers will place Juno in a slowly deteriorating orbit that will eventually force it to dive into the planet. This is so that none of its potentially life-bearing moons, like Europa, can get contaminated.
Due to Juno’s limited lifespan, the science mission begins almost immediately. The spacecraft’s instruments will come online in two days, when Juno begins its first 53-day elongated orbit. As it enters Jupiter’s intense radiation belts, Juno won’t send any data back to Earth, so scientists will have to wait until the end of August before they can collect large amounts of information about the planet. Shorter, more closely spaced courses will follow in 2017.
Jupiter, of course, has been extensively explored before by NASA’s Galileo probe, which studied both the stormy, colorful gas giant and its extensive system of moons, starting about 20 years ago. Juno will try to dig deeper into Jupiter’s interior with two magnetometers, which will allow scientists to map the planet’s magnetic field. They hope to understand exactly how that intense magnetic field is generated and how hydrogen behaves at the very high pressure in the planet’s center. Other instruments on board will measure Jupiter’s gravitational field, cloud structure and the amount of water in Jupiter’s atmosphere.
And now, thanks to Monday night’s precise maneuvers, Juno has a chance to fulfill the promise of its hefty science mission. “Tonight Juno sang for us, and it was a song of perfection,” Rick Nybakken, Juno’s project manager at the Jet Propulsion Laboratory, said at a late night press conference.
As much of the United States celebrated the 240th anniversary of the United States Declaration of Independence, NASA paid tribute to the nation of Washington, Jefferson, and Lincoln in its own way. Again, NASA had made it look easy, but it certainly wasn’t. No other country has ever sent a spacecraft into orbit around Jupiter, and now America has done it twice. Happy Birthday indeed.
List image by NASA