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http://www.jpl.nasa.gov/news/news.php?feature=6648

Mission Prepares for Next Jupiter Pass
Jet Propulsion Laboratory
October 14, 2016

Mission managers for NASA's Juno mission to Jupiter have decided to postpone the upcoming burn of its main rocket motor originally scheduled for Oct.
19. This burn, called the period reduction maneuver (PRM), was to reduce Juno's orbital period around Jupiter from 53.4 to 14 days. The decision
was made in order to further study the performance of a set of valves
that are part of the spacecraft's fuel pressurization system. The period reduction maneuver was the final scheduled burn of Juno's main engine.

"Telemetry indicates that two helium check valves that play an important
role in the firing of the spacecraft's main engine did not operate as
expected during a command sequence that was initiated yesterday," said
Rick Nybakken, Juno project manager at NASA's Jet Propulsion Laboratory
in Pasadena, California. "The valves should have opened in a few seconds,
but it took several minutes. We need to better understand this issue before moving forward with a burn of the main engine."

After consulting with Lockheed Martin Space Systems of Denver and NASA Headquarters, Washington, the project decided to delay the PRM maneuver
at least one orbit. The most efficient time to perform such a burn is
when the spacecraft is at the part of its orbit which is closest to the planet. The next opportunity for the burn would be during its close flyby
of Jupiter on Dec. 11.

Mission designers had originally planned to limit the number of science instruments on during Juno's Oct. 19 close flyby of Jupiter. Now, with
the period reduction maneuver postponed, all of the spacecraft's science instruments will be gathering data during the upcoming flyby.

"It is important to note that the orbital period does not affect the quality of the science that takes place during one of Juno's close flybys of Jupiter," said Scott Bolton, principal investigator of Juno from the Southwest Research Institute in San Antonio. "The mission is very flexible that way. The
data we collected during our first flyby on August 27th was a revelation,
and I fully anticipate a similar result from Juno's October 19th flyby."

The Juno spacecraft launched on Aug. 5, 2011, from Cape Canaveral, Florida, and arrived at Jupiter on July 4, 2016.

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. Lockheed Martin Space Systems, Denver, built the spacecraft. Caltech in Pasadena, California, manages JPL for NASA.

More information on the Juno mission is available at:

http://www.nasa.gov/juno

The public can follow the mission on Facebook and Twitter at:

http://www.facebook.com/NASAJuno

http://www.twitter.com/NASAJuno

News Media Contact
DC Agle
Jet Propulsion Laboratory, Pasadena, Calif.
818-393-9011
agle@jpl.nasa.gov

Dwayne Brown / Laurie Cantillo
NASA Headquarters, Washington
202-358-1726 / 202-358-1077
dwayne.c.brown@nasa.gov / laura.l.cantillo@nasa.gov

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