{"id":14855,"date":"2017-02-21T23:29:40","date_gmt":"2017-02-21T15:29:40","guid":{"rendered":"https:\/\/wp-productionenv-bjg9h2g2bgg5b8aa.southeastasia-01.azurewebsites.net\/news\/nasas-juno-spacecraft-to-remain-in-current-orbit-around-jupiter\/"},"modified":"2017-02-21T23:29:40","modified_gmt":"2017-02-21T15:29:40","slug":"nasas-juno-spacecraft-to-remain-in-current-orbit-around-jupiter","status":"publish","type":"post","link":"https:\/\/starpath.global\/news\/nasas-juno-spacecraft-to-remain-in-current-orbit-around-jupiter\/","title":{"rendered":"NASA\u2019s Juno spacecraft to remain in current orbit around Jupiter"},"content":{"rendered":"
\"\"
Artist\u2019s concept of the Juno spacecraft at Jupiter. Credit: NASA\/JPL-Caltech<\/figcaption><\/figure>\n

Concerns about the health of the Juno spacecraft\u2019s main engine have compelled NASA managers to keep the research probe in its current arcing, high-altitude orbit around Jupiter, a decision that will delay the full science return from the $1.1 billion mission but should still allow it to meet all predetermined objectives.<\/p>\n

Juno fired its main engine to brake into orbit around Jupiter on July 4, 2016, maneuvering into an egg-shaped 53-day orbit that takes the spacecraft several million miles from the giant planet on each circuit.<\/p>\n

At the low end of the orbit, the spacecraft passes within 3,000 miles (5,000 kilometers) from Jupiter\u2019s cloud tops, permitting Juno\u2019s instruments to peer deep into the atmosphere, measure the planet\u2019s extreme magnetic field and radiation belts, observe its auroras, and take the first detailed images of its poles.<\/p>\n

But engineers called off another engine burn planned for Oct. 19 to put Juno in a tighter 14-day orbit, the science perch envisioned by mission managers since the project\u2019s inception. Most of Juno\u2019s scientific observations occur when the probe is closer to the planet, and the 14-day orbit was designed to give researchers rapid-fire data returns during close approaches every two weeks.<\/p>\n

Ground controllers noticed two helium check valves inside the spacecraft\u2019s main propulsion system did not behave as expected during pressurization of Juno\u2019s propellant tanks about a week before the planned Oct. 19 engine firing. The valves opened in several seconds before previous engine burns, but took several minutes to open in October.<\/p>\n

Rick Nybakken, Juno\u2019s project manager at NASA\u2019s Jet Propulsion Laboratory, told Spaceflight Now that engineers recommended canceling the maneuver and keeping the craft in its current 53-day orbit after a multi-month investigation.<\/p>\n

\u201cThe project recommended not doing the burn,\u201d Nybakken said in a Feb. 17 interview. \u201cWe\u2019re in a great science orbit, the spacecraft is healthy, the instruments are healthy. We\u2019re getting incredible science, and it\u2019s teaching us more about Jupiter, and there are a lot of very interesting surprises about Jupiter, so we recommended not to take any additional risk that might jeopardize that \u2014 not to do this burn \u2014 and ultimately NASA Headquarters agreed with that recommendation.\u201d<\/p>\n

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This diagram shows Juno\u2019s original flight plan, in which the spacecraft would have completed two 53-day orbits, then transitioned into a lower 14-day science orbit around Jupiter. NASA has decided to keep the spacecraft in the 53-day orbit for the rest of the mission. Credit: NASA\/JPL-Caltech<\/figcaption><\/figure>\n

According to Nybakken, experts considered an option in which Juno\u2019s Leros 1b main engine, designed and built by Moog-ISP in the United Kingdom, could have fired in a backup \u201cblow-down\u201d mode using residual tank pressure, bypassing the suspect check valves. In a normal burn, the check valves would actuate to regulate pressure in the propellant system feeding the thruster.<\/p>\n

Officials decided the risk of doing a \u201cblow-down\u201d burn was too great, Nybakken said. Any problem during such an engine firing could have stranded Juno midway between the 53-day and 14-day orbits in a less optimal perch for science observations.<\/p>\n

In the 53-day orbit, Juno will avoid flying through Jupiter\u2019s shadow, keeping the craft\u2019s power-generating solar panels in sunlight. If Juno ended up in an unplanned lower orbit because of a sub-optimal engine burn, the probe would have flown through a series of eclipses in 2019, starving it of sunlight and likely ending the mission.<\/p>\n

The choice not to execute the orbit-lowering burn preserves the option to use Juno\u2019s smaller maneuvering thrusters to steer clear of Jupiter\u2019s shadow and keep the mission going beyond 2019.<\/p>\n

\u201cIt wasn\u2019t so much that the risk was unacceptable, it\u2019s just that if anything off-nominal were to happen, you bring in these mission-ending eclipses in 2019,\u201d Nybakken said. \u201cIn our current orbit, the size of the orbit is large enough, and the time of the orbit helps give us the operational latitude to avoid those eclipses.\u201d<\/p>\n

Nybakken said the inquiry into Juno\u2019s propulsion woes did not determine a root cause for the sticky valves. Officials quickly decided against using the valves for a \u201cregulated\u201d burn, and instead studied the backup \u201cblow-down\u201d option before eventually concluding Juno\u2019s orbit should not be lowered at all.<\/p>\n

\u201cAt a high level, one of the leading theories is that we can have a very low level of interaction at the vapor level between fuel and oxidizer, and it can create products that can interfere with proper valve operation,\u201d Nybakken said. \u201cBeyond that, it is kind of to be determined. We didn\u2019t require root cause to realize the valves are not working as intended.\u201d<\/p>\n

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NASA\u2019s Juno spacecraft soared directly over Jupiter\u2019s south pole when JunoCam acquired this image on February 2, 2017 at 6:06 a.m. PT (9:06 a.m. ET), from an altitude of about 62,800 miles (101,000 kilometers) above the cloud tops. This image from Juno\u2019s JunoCam camera was processed by citizen scientist John Landino. Credit: NASA\/JPL-Caltech\/SwRI\/MSSS\/John Landino<\/figcaption><\/figure>\n

Engineers ruled out any link between Juno\u2019s propulsion problem and engine failures on two geostationary communications satellites last year, Nybakken said.<\/p>\n

The commercial Intelsat 33e and the U.S. Navy\u2019s MUOS 5 communications satellites were to use on-board engines to raise their orbits to geostationary altitude 22,300 miles (35,800 kilometers) above Earth\u2019s equator after launching in June and August 2016. Both satellites had to use backup thrusters to finish the job.<\/p>\n

Nybakken said those engine failures were unrelated to the issue aboard Juno, and engineers with JPL and Lockheed Martin \u2014 Juno\u2019s prime contractor \u2014 cleared the Leros 1b engine on the Jupiter orbiter in October, before encountering the sticky check valves.<\/p>\n

\u201cThere were a couple of failures last fall that we looked into, and we were able to determine that those failures did not represent any sort of increased risk to Juno,\u201d Nybakken said. \u201cAnd after we completed that investigation, we were, in fact, planning to go ahead with this maneuver.\u201d<\/p>\n

One benefit of Juno\u2019s predicament is the higher 53-day orbit will keep the spacecraft away from the worst of Jupiter\u2019s intense radiation belts, which harbor hazards that mission designers believed would limit the mission\u2019s duration to some time in 2018.<\/p>\n

\u201cIt turns out in the 53-day orbits, we cross the equator, where the radiation belts are, much farther out, so we have much less radiation dose,\u201d Nybakken said. \u201cOf course, with the orbits being larger, the dose as a function of time is much slower as well.\u201d<\/p>\n

Juno\u2019s next close pass by Jupiter is set for March 27, completing its fifth orbit of the planet since last year\u2019s arrival.<\/p>\n

\u201cJuno is healthy, its science instruments are fully operational, and the data and images we\u2019ve received are nothing short of amazing,\u201d said Thomas Zurbuchen, associate administrator for NASA\u2019s science mission directorate in Washington, in a statement. \u201cThe decision to forego the burn is the right thing to do \u2014 preserving a valuable asset so that Juno can continue its exciting journey of discovery.\u201d<\/p>\n

The Juno mission is funded through July 2018, for a total of 12 science orbits, down from the 32 science orbits originally planned, NASA said in a statement.<\/p>\n

Juno\u2019s science team can then propose to continue the mission for another two years as part of NASA\u2019s senior review process, in which a panel of independent researchers recommend to the agency which of its planetary science missions should continue to receive federal funding.<\/p>\n

\u201cJuno is providing spectacular results, and we are rewriting our ideas of how giant planets work,\u201d said Scott Bolton, the mission\u2019s principal investigator from the Southwest Research Institute in San Antonio. \u201cThe science will be just as spectacular as with our original plan.\u201d<\/p>\n

\u201cWe\u2019re very excited about what we\u2019ve seen so far, and every time we fly by the planet it\u2019s like Christmas time,\u201d Nybakken said. \u201cThe data is stunning.\u201d<\/p>\n

Email the author.<\/i><\/b><\/p>\n

Follow Stephen Clark on Twitter: @StephenClark1.<\/strong><\/em><\/p>\n","protected":false},"excerpt":{"rendered":"

Artist\u2019s concept of the Juno spacecraft at Jupiter. Credit: NASA\/JPL-Caltech Concerns about the health of the Juno spacecraft\u2019s main engine have compelled NASA managers to keep the research probe in its current arcing, high-altitude orbit around Jupiter, a decision that will delay the full science return from the $1.1 billion mission but should still allow […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"inline_featured_image":false,"footnotes":"","_links_to":"","_links_to_target":""},"categories":[2],"tags":[1183,1929,1606,3405,472,2020,1561,2612],"class_list":["post-14855","post","type-post","status-publish","format-standard","hentry","category-news","tag-jet-propulsion-laboratory","tag-juno","tag-jupiter","tag-leros-1b","tag-lockheed-martin","tag-new-frontiers","tag-planetary-science","tag-swri"],"acf":[],"_links":{"self":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/14855"}],"collection":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/comments?post=14855"}],"version-history":[{"count":0,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/14855\/revisions"}],"wp:attachment":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media?parent=14855"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/categories?post=14855"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/tags?post=14855"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}