- #101
1oldman2
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Minor set back to contingency mode, hoping all ends up well. 
http://spaceflight101.com/juno-prm-postponed/
Instead of spiraling down into a two-week science orbit around Jupiter, NASA’s Juno spacecraft will have to remain in a highly elliptical orbit for at least one more lap around the gaseous world due to a suspect signature seen in the preparatory steps for the critical main engine burn originally planned for next week.
After operating all its instruments for the ‘perijove’ passage, Juno was outbound again, set for a routine Orbital Trim Maneuver ahead of passing the high point of its orbit on September 23 and starting the inbound leg to what was known as ‘Period Reduction Maneuver’ - a rocket-powered braking maneuver to bring down the apojove distance and place the spacecraft into its two-week science orbit.
The engine firing was planned to begin around 18 UTC on October 19, eleven minutes before Juno passed only 4,180 Kilometers above Jupiter’s cloud tops. This maneuver is the final scheduled use of Juno’s LEROS-1B main engine that was responsible for a pair of Deep Space Maneuvers in 2012 and the Jupiter Orbit Insertion maneuver on July 4.
"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 JPL. "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."
With a third Capture Orbit added to the mission, Juno is now looking forward to its second close pass by Jupiter that can be utilized for science data collection. Due to the mission’s orbital design, the close perijove passes of the Capture Orbits and the planned Science Orbit are very similar in terms of altitude and flight path - taking Juno from north to south with closest approach near the equator, offering excellent views of Jupiter’s polar regions.
The first close pass of Juno already revealed tantalizing new views of Jupiter provided by the spacecraft ’s sole camera instrument, JunoCam. Data captured by the other instruments was by no means less spectacular, but scientists needed time to fully dive in and analyze the first close-up data peering below Jupiter’s dense cloud tops.
Passing Jupiter on Wednesday, Juno will be outbound again with its next close pass of the planet on December 11 which will be the next opportunity for the Period Reduction Maneuver - pending evaluations of the suspect check valve signature.
The option of a third Capture Orbit has be prepared as part of numerous contingency scenarios worked out for this mission, however, there is some urgency in getting Juno down into the science orbit due to the limited lifetime of the spacecraft in the extreme radiation environment of Jupiter.
Juno was set for a total of 36 orbits around Jupiter with its science phase lasting until February 6, 2018. Pending reviews of the spacecraft ’s performance in the harsh radiation environment, a short mission extension will be assessed when the time comes.
Here is what JPL says.
http://www.nasa.gov/feature/jpl/mission-prepares-for-next-jupiter-pass
JUNO MISSION STATUS
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."
http://spaceflight101.com/juno-prm-postponed/
Instead of spiraling down into a two-week science orbit around Jupiter, NASA’s Juno spacecraft will have to remain in a highly elliptical orbit for at least one more lap around the gaseous world due to a suspect signature seen in the preparatory steps for the critical main engine burn originally planned for next week.
After operating all its instruments for the ‘perijove’ passage, Juno was outbound again, set for a routine Orbital Trim Maneuver ahead of passing the high point of its orbit on September 23 and starting the inbound leg to what was known as ‘Period Reduction Maneuver’ - a rocket-powered braking maneuver to bring down the apojove distance and place the spacecraft into its two-week science orbit.
The engine firing was planned to begin around 18 UTC on October 19, eleven minutes before Juno passed only 4,180 Kilometers above Jupiter’s cloud tops. This maneuver is the final scheduled use of Juno’s LEROS-1B main engine that was responsible for a pair of Deep Space Maneuvers in 2012 and the Jupiter Orbit Insertion maneuver on July 4.
"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 JPL. "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."
With a third Capture Orbit added to the mission, Juno is now looking forward to its second close pass by Jupiter that can be utilized for science data collection. Due to the mission’s orbital design, the close perijove passes of the Capture Orbits and the planned Science Orbit are very similar in terms of altitude and flight path - taking Juno from north to south with closest approach near the equator, offering excellent views of Jupiter’s polar regions.
The first close pass of Juno already revealed tantalizing new views of Jupiter provided by the spacecraft ’s sole camera instrument, JunoCam. Data captured by the other instruments was by no means less spectacular, but scientists needed time to fully dive in and analyze the first close-up data peering below Jupiter’s dense cloud tops.
Passing Jupiter on Wednesday, Juno will be outbound again with its next close pass of the planet on December 11 which will be the next opportunity for the Period Reduction Maneuver - pending evaluations of the suspect check valve signature.
The option of a third Capture Orbit has be prepared as part of numerous contingency scenarios worked out for this mission, however, there is some urgency in getting Juno down into the science orbit due to the limited lifetime of the spacecraft in the extreme radiation environment of Jupiter.
Juno was set for a total of 36 orbits around Jupiter with its science phase lasting until February 6, 2018. Pending reviews of the spacecraft ’s performance in the harsh radiation environment, a short mission extension will be assessed when the time comes.
Here is what JPL says.
http://www.nasa.gov/feature/jpl/mission-prepares-for-next-jupiter-pass
JUNO MISSION STATUS
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."
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