NASA's Juno mission, launched nearly
five years ago, will soon reach its final destination: the most massive planet
in our solar system, Jupiter. On the evening of July 4, at roughly 9 p.m. PDT
(12 a.m. EDT, July 5), the spacecraft will complete a burn of its main engine,
placing it in orbit around the king of planets.
During
Juno's orbit-insertion phase, or JOI, the spacecraft will perform a series of
steps in preparation for a main engine burn that will guide it into orbit. At
6:16 p.m. PDT (9:16 p.m. EDT), Juno will begin to turn slowly away from the sun
and toward its orbit-insertion attitude. Then 72 minutes later, it will make a
faster turn into the orbit-insertion attitude.
At
7:41 p.m. PDT (10:41 p.m. EDT), Juno switches to its low-gain antenna.
Fine-tune adjustments are then made to the spacecraft's attitude. Twenty-two
minutes before the main engine burn, at 7:56 p.m. PDT (10:56 p.m. EDT), the
spacecraft spins up from 2 to 5 revolutions per minute (RPM) to help stabilize
it for the orbit insertion burn.
At
8:18 p.m. PDT (11:18 p.m. EDT), Juno's 35-minute main-engine burn will begin.
This will slow it enough to be captured by the giant planet’s gravity. The burn
will impart a mean change in velocity of 1,212 mph (542 meters a second) on the
spacecraft. It is performed in view of Earth, allowing its progress to be
monitored by the mission teams at NASA's Jet Propulsion Laboratory in Pasadena,
California, and Lockheed Martin Space Systems in Denver, via signal reception
by Deep Space Network antennas in Goldstone, California, and Canberra,
Australia.
After
the main engine burn, Juno will be in orbit around Jupiter. The spacecraft will
spin down from 5 to 2 RPM, turn back toward the sun, and ultimately transmit
telemetry via its high-gain antenna.
Juno
starts its tour of Jupiter in a 53.5-day orbit. The spacecraft saves fuel by
executing a burn that places it in a capture orbit with a 53.5-day orbit
instead of going directly for the 14-day orbit that will occur during the
mission's primary science collection period. The 14-day science orbit phase
will begin after the final burn of the mission for Juno’s main engine on
October 19.
JPL
manages the Juno mission for NASA. The mission's principal investigator is
Scott Bolton of Southwest Research Institute in San Antonio. The mission is
part of NASA's New Frontiers Program, managed at the agency's Marshall Space
Flight Center in Huntsville, Alabama, for NASA's Science Mission Directorate.
Lockheed Martin Space Systems in Denver built the spacecraft.
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