Juno is a NASA space probe orbiting the planet Jupiter after entering orbit on 11:53pm EDST,[4] July 4th, 2016; the prelude to 20 months[5] of scientific data collection to be followed by a planned deorbit.[5] It was launched from Cape Canaveral Air Force Station on August 5, 2011, as part of the New Frontiers program,[6] and ranged into Jupiter's orbit on July 4, 2016.[4][7]
Juno's maneuver on 4 July has put it into a polar orbit to study Jupiter's composition, gravity field, magnetic field, and polar magnetosphere. Juno will also search for clues about how the planet formed, including whether it has a rocky core, the amount of water present within the deep atmosphere, mass distribution, and its deep winds, which can reach speeds of 618 kilometers per hour (384 mph).[8]
Juno is only the second spacecraft to orbit Jupiter and the first solar powered craft to do so, following behind the nuclear powered Galileo probe, which orbited from 1995 to 2003.[5]
Unlike all the earlier nuclear powered spacecraft to the outer planets,[5] the Juno spacecraft is powered only by solar arrays, commonly used by satellites orbiting Earth and working in the inner Solar System, whereas radioisotope thermoelectric generators are commonly used for missions to the outer Solar System and beyond. For Juno, however, three solar array wings, the largest ever deployed on a planetary probe, play an integral role in stabilizing the spacecraft as well as generating power.[9]
“ The spacecraft's name comes from Greco-Roman mythology. The god Jupiter drew a veil of clouds around himself to hide his mischief, but his wife, the goddess Juno, was able to peer through the clouds and see Jupiter's true nature. ”
Overview[edit]
Juno's interplanetary trajectory; tick marks at 30-day intervals.
File:Juno spacecraft trajectory animation.webm
Juno spacecraft trajectory animation
Juno completed a five-year cruise to Jupiter, arriving on July 4, 2016.[7] The spacecraft traveled over a total distance of roughly 2.8 billion kilometers (18.7 AU; 1.74 billion miles) to reach Jupiter.[12] The spacecraft will orbit Jupiter 37 times over the course of 20 months.[4][13] Juno's trajectory used a gravity assist speed boost from Earth, accomplished through an Earth flyby in October 2013, two years after its launch on August 5, 2011.[14] On July 5, 2016, the spacecraft performed an orbit insertion burn to slow it enough to allow capture. It will make two 53-day orbits before performing another burn on October 19 that will bring it into a 14-day polar orbit.
Once in the 14-day orbit, infrared and microwave instruments will begin to measure the thermal radiation emanating from deep within Jupiter's atmosphere. These observations will complement previous studies of its composition by assessing the abundance and distribution of water, and therefore oxygen. This data will provide insight into Jupiter's origins. Juno will also investigate the convection that drives general circulation patterns in Jupiter's atmosphere. Other instruments aboard Juno will gather data about its gravitational field and polar magnetosphere. The Juno mission is set to conclude in February 2018, after completing 37 orbits of Jupiter, when the probe will be de-orbited to burn up in Jupiter's outer atmosphere,[4][13] so as to avoid any possibility of impact and biological contamination of one of its moons.[15]
Flight trajectory[edit]
Launch[edit]
Juno was launched atop the Atlas V at Cape Canaveral Air Force Station, Florida. The Atlas V (AV-029) used a Russian-designed and -built RD-180 main engine, powered by kerosene and liquid oxygen. At ignition it underwent checkout 3.8 seconds prior to the ignition of five strap-on solid rocket boosters (SRBs). Following SRB burnout, approximately 1 minute 33 seconds into the flight, two of the spent boosters fell away from the vehicle, followed 1.5 seconds later by the remaining three. When heating levels had dropped below predetermined limits, the payload fairing that protected Juno during transit through the thickest part of the atmosphere separated, about 3 minutes 24 seconds into the flight. The Atlas V main engine cut off 4 minutes 26 seconds after liftoff. Sixteen seconds later, the Centaur second stage ignited and burned for approximately 6 minutes, putting the satellite into an initial parking orbit.[16] The vehicle coasted for approximately 30 minutes, and then the Centaur was re-ignited for a second firing of 9 minutes, placing the spacecraft on an Earth escape trajectory in a heliocentric orbit.
Prior to separation, the Centaur stage used onboard reaction engines to spin Juno up to 1.4 RPM. About 54 minutes after launch, the spacecraft separated from the Centaur and began to extend its solar panels. Following the full deployment and locking of the solar panels, Juno's batteries began to recharge. Deployment of the solar panels reduced Juno's spin rate by two-thirds. The probe is spun to ensure stability during t