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This diagram shows the Juno spacecraft's orbits, including
its two long, stretched-out capture orbits. The spacecraft's position on July 31
is indicated at left. Credit: NASA/JPL-Caltech
Five years after departing Earth, and a month after
slipping into orbit around Jupiter, NASA's Juno spacecraft is nearing a turning
point. On July 31 at 12:41 p.m. PDT (3:41 p.m. EDT), Juno will reach the
farthest point in its orbit of Jupiter for the first time, known as “apojove,” 5
million miles (8.1 million kilometers) from the giant planet. After that point,
Jupiter's gravitational grip on Juno will cause the spacecraft to begin falling
back toward the planet for another pass, this time with its scientific eyes
wide open.
The spacecraft is currently executing the first of two long
orbits prior to beginning its science mission. Each capture orbit is nearly two
months long -- quite the wait for the mission's eager team of scientists -- but
it's nothing compared to the long wait the team endured on the trek to Jupiter.
Juno launched on Aug. 5, 2011. The spacecraft took a long,
looping path around the inner solar system to set up an Earth flyby, in which
our planet's gravity flung the spinning probe onward toward Jupiter.
"For five years we've been focused on getting to Jupiter.
Now we're there, and we're concentrating on beginning dozens of flybys of Jupiter
to get the science we're after," said Scott Bolton, Juno principal
investigator at Southwest Research Institute in San Antonio.
Juno arrived at Jupiter on July 4, firing its main rocket
engine as planned for 35 minutes. The flawless maneuver allowed Jupiter's
gravity to capture the solar powered spacecraft into the first of two 53.4-day-long
orbits, referred to as capture orbits. Following the capture orbits, Juno will
fire its engine once more to shorten its orbital period to 14 days and begin
its science mission.
But before that happens, on Aug. 27, Juno must finish its
first lap around Jupiter, with a finish line that represents the mission's closest
pass over the gas giant. During the encounter, Juno will skim past Jupiter at a
mere 2,600 miles (4,200 kilometers) above the cloud tops.
Juno's science instruments were turned off during orbit
insertion, to simplify spacecraft operations during that critical maneuver. In
contrast, all the instruments will be collecting data during the Aug. 27 pass, which
serves as a trial run before the mission gets to work collecting the precious
data it came for.
"We're in an excellent state of health, with the
spacecraft and all the instruments fully checked out and ready for our first
up-close look at Jupiter," said Rick Nybakken, Juno project manager at
NASA's Jet Propulsion Laboratory, Pasadena, California.
With its powerful suite of science instruments, Juno will
probe Jupiter's deep structure, atmospheric circulation and the high-energy
physics of its magnetic environment. What Juno finds there will reveal
important clues to Jupiter's formation and evolution, along with insights about
how our planetary system and others are built.
JPL manages the Juno mission for the principal
investigator, Scott Bolton, of Southwest Research Institute in San Antonio.
Juno is part of NASA's New Frontiers Program, which is managed at NASA's
Marshall Space Flight Center in Huntsville, Alabama, for NASA's Science Mission
Directorate. Caltech in Pasadena manages JPL for NASA.
This artist's concept depicts the Juno spacecraft above
Jupiter. The spacecraft will next fly by the planet on Aug. 27, in the
mission's first up-close science pass. Credit: NASA/JPL-Caltech