Tonight is the night, my fellow space nerds. After five years and 445 million miles, NASA’s Juno mission is about to arrive at Jupiter, becoming the second spacecraft in history to orbit the gas giant. We hope.
First, Juno has to perform a high-risk sequence of maneuvers culminating in a 35-minute main engine burn at 11:18 PM ET (8:16 PM PT). That burn causes the spacecraft to shed some 1,212 mph (542 meters per second) of velocity; enough to be captured by Jupiter’s gravity.
The key events of the Juno orbital insertion (JOI) begin around 10:30 PM ET, when Juno pivots away from the sun for the first and only time to position its engine for the burn. The solar-powered spacecraft will have to rely on batteries for the duration of the JOI, and it’ll only be able to talk to Earth using its low-gain antenna, with a signal strength about a billion times weaker than a cell phone call.
In brief, here’s how things are going to go down (all times are Eastern):
10:28 PM: Juno pivots away from the sun and toward its orbital insertion attitude.
10:56 PM: Juno “spins up” from 2 to 5 revolutions per minute in order to stabilize itself for the main engine burn.
11:18 PM: The burn begins.
11:53 PM: The burn ends, leaving Juno in its first, 53.5 day orbit.
11:55 PM: The spacecraft slows back down to 2 rpm.
12:30 AM: Juno re-orients toward the sun to recharge its batteries. At this point, if all signals look good, we can all relax.
Before, during, and after the JOI, Juno’s mission team will be listening for a series of status tones from the spacecraft, using antennas at the Deep Space Network stations in Goldstone, California, and Canberra, Australia. These tones tell NASA that various milestones have been reached, and most importantly, that the deceleration burn has ended.
If anything goes wrong—if the engine doesn’t fire, if the flight computer crashes, or if a small piece of dust damages the spacecraft—Juno will wind up in the wrong place, and the mission’s kaput. There’s no way for NASA to fix any problems that arise during the JOI, because it takes 48 minutes to send a signal from Earth. In other words, things are going to be a wee bit tense around the Jet Propulsion Laboratory tonight.
If everything does work, Juno will spend the next 20 months taking unprecedented, high-resolution images of Jupiter, and peering deep beneath the gas giant’s cloud tops to discover what lies at its center.
NASA will live stream tonight’s proceedings in all of their nail-biting glory beginning at 10:30 PM ET. Follow along right here.
Update 11:44 PM ET: Juno is in orbit! NASA has confirmed that the main engine has burned enough for Juno to be captured by Jupiter. For the next few minutes, Juno will be making the orbit more optimal, before it pivots back toward the sun to recharge its batteries.
Update 11:54 PM ET: The burn is complete! Welcome to Jupiter!