Artists concept of the Juno spacecraft at Jupiter. Credit: NASA/JPL-Caltech
Concerns about the health of the Juno spacecrafts 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.
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.
At the low end of the orbit, the spacecraft passes within 3,000 miles (5,000 kilometres) from Jupiters cloud tops, permitting Junos instruments to peer deep into the atmosphere, measure the planets extreme magnetic field and radiation belts, observe its auroras, and take the first detailed images of its poles.
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 projects inception.Most of Junos 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.
Ground controllers noticed two helium check valves inside the spacecrafts main propulsion system did not behave as expected during pressurization of Junos 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.
Rick Nybakken, Junos project manager at NASAs 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.
The project recommended not doing the burn, Nybakken said in a Feb. 17 interview. Were in a great science orbit, the spacecraft is healthy, the instruments are healthy. Were getting incredible science, and its 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 not to do this burn and ultimately NASA Headquarters agreed with that recommendation.
According to Nybakken, experts considered an option in which Junos Leros 1b main engine, designed and built by Moog-ISP in the United Kingdom, could have fired in a backup blow-down 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.
Officials decided the risk of doing a blow-down 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.
In the 53-day orbit, Juno will avoid flying through Jupiters shadow, keeping the crafts 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.
The choice not to execute the orbit-lowering burn preserves the option to use Junos smaller maneuvering thrusters to steer clear of Jupiters shadow and keep the mission going beyond 2019.
It wasnt so much that the risk was unacceptable, its just that if anything off-nominal were to happen, you bring in these mission-ending eclipses in 2019, Nybakken said. In 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.
Nybakken said the inquiry into Junos propulsion woes did not determine a root cause for the sticky valves. Officials quickly decided against using the valves for a regulated burn, and instead studied the backup blow-down option before eventually concluding Junos orbit should not be lowered at all.
At 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, Nybakken said. Beyond that, it is kind of to be determined. We didnt require root cause to realize the valves are not working as intended.
Engineers ruled out any link between Junos propulsion problem and engine failures on two geostationary communications satellites last year, Nybakken said.
The commercial Intelsat 33e and the U.S. Navys MUOS 5 communications satellites were to use on-board engines to raise their orbits to geostationary altitude 22,300 miles (35,800 kilometres) above Earths equator after launching in June and August 2016. Both satellites had to use backup thrusters to finish the job.
Nybakken said those engine failures were unrelated to the issue aboard Juno, and engineers with JPL and Lockheed Martin Junos prime contractor cleared the Leros 1b engine on the Jupiter orbiter in October, before encountering the sticky check valves.
There 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, Nybakken said. And after we completed that investigation, we were, in fact, planning to go ahead with this maneuver.
One benefit of Junos predicament is the higher 53-day orbit will keep the spacecraft away from the worst of Jupiters intense radiation belts, which harbour hazards that mission designers believed would limit the missions duration to some time in 2018.
It 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, Nybakken said. Of course, with the orbits being larger, the dose as a function of time is much slower as well.
Junos next close pass by Jupiter is set for March 27, completing its fifth orbit of the planet since last years arrival.
Juno is healthy, its science instruments are fully operational, and the data and images weve received are nothing short of amazing, said Thomas Zurbuchen, associate administrator for NASAs science mission directorate in Washington, in a statement. The decision to forego the burn is the right thing to do preserving a valuable asset so that Juno can continue its exciting journey of discovery.
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.
Junos science team can then propose to continue the mission for another two years as part of NASAs 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.
Juno is providing spectacular results, and we are rewriting our ideas of how giant planets work, said Scott Bolton, the missions principal investigator from the Southwest Research Institute in San Antonio. The science will be just as spectacular as with our original plan.
Were very excited about what weve seen so far, and every time we fly by the planet its like Christmas time, Nybakken said. The data is stunning.
Email the author.
Follow Stephen Clark on Twitter: @StephenClark1.
See the article here:
NASA's Juno spacecraft to remain in current orbit around Jupiter - Astronomy Now Online
- I Spy With My Little Eye… - November 7th, 2009 [November 7th, 2009]
- A Crack Opens in the Ethiopian Landscape, Preparing the Way for a New Sea | 80beats - November 8th, 2009 [November 8th, 2009]
- The Politics of Addiction | The Intersection - November 8th, 2009 [November 8th, 2009]
- Finally! An iPhone App That Lets You Track Your Bathroom Habits | Discoblog - November 8th, 2009 [November 8th, 2009]
- Don’t Pack Your Bags Yet—New Planet-Finder Hobbled by Electronic Glitch | 80beats - November 8th, 2009 [November 8th, 2009]
- In Controversial Scent Lineups, a Dog’s Nose Picks Out the Perp | 80beats - November 8th, 2009 [November 8th, 2009]
- Are You a Cognitive Miser? | Cosmic Variance - November 8th, 2009 [November 8th, 2009]
- The Secret Lives and Loves of Great White Sharks | 80beats - November 8th, 2009 [November 8th, 2009]
- Britain’s New Protected Minority: Tree-Huggers | Discoblog - November 8th, 2009 [November 8th, 2009]
- Inspired by Maple Seeds, a Robotic Whirligig Takes To The Skies | Discoblog - November 8th, 2009 [November 8th, 2009]
- New Statesman on Accommodationism | The Intersection - November 8th, 2009 [November 8th, 2009]
- Laser-Powered Robot Climbs to Victory in the Space-Elevator Contest | 80beats - November 8th, 2009 [November 8th, 2009]
- Checking Back In With SEAPLEX | The Intersection - November 8th, 2009 [November 8th, 2009]
- Podcast: An Embarrassment of Genomes | The Loom - November 8th, 2009 [November 8th, 2009]
- A Baby Neutron Star, Swaddled in a Carbon Atmosphere | 80beats - November 8th, 2009 [November 8th, 2009]
- Butterfliiiies… iiinnnn… SPPPAAAAACCCCEEEEE! | Bad Astronomy - November 8th, 2009 [November 8th, 2009]
- My Slate Dialogue with Michael Specter Begins | The Intersection - November 8th, 2009 [November 8th, 2009]
- Musical, Fahrvergnügen-Inspired Staircase Makes Commuters Less Lazy | Discoblog - November 8th, 2009 [November 8th, 2009]
- Laser-Etched Fruit Is an Answer in Search of a Problem | Discoblog - November 8th, 2009 [November 8th, 2009]
- Ares and the carnivals | Bad Astronomy - November 8th, 2009 [November 8th, 2009]
- Toddler Gets a Telescoping, Prosthetic Arm Bone That Grows With Him | 80beats - November 8th, 2009 [November 8th, 2009]
- Neutered HIV Virus Delivers Treatment to Fatally Ill Boys | 80beats - November 8th, 2009 [November 8th, 2009]
- Specter’s First Reply: Denialism Kills People | The Intersection - November 8th, 2009 [November 8th, 2009]
- LRO sees a Moonslide | Bad Astronomy - November 8th, 2009 [November 8th, 2009]
- Al Gore’s New Book: A Focus on Solutions | The Intersection - November 8th, 2009 [November 8th, 2009]
- The Universe Has Us in Its Crosshairs | Bad Astronomy - November 8th, 2009 [November 8th, 2009]
- Makers of Universes | Cosmic Variance - November 8th, 2009 [November 8th, 2009]
- Can Your Pet Catch & Spread Swine Flu? Yes, If Your Pet’s a Ferret | 80beats - November 8th, 2009 [November 8th, 2009]
- Droid 2.0 Vs iPhone | The Intersection - November 8th, 2009 [November 8th, 2009]
- Tangled Bank News: An Excerpt and More | The Loom - November 8th, 2009 [November 8th, 2009]
- LHC Shut Down By Wayward Baguette, Dropped by Bird Saboteur | Discoblog - November 8th, 2009 [November 8th, 2009]
- Careidolia | Bad Astronomy - November 8th, 2009 [November 8th, 2009]
- Slate Reply to Specter Up–We Need a National Dialogue on Synthetic Biology | The Intersection - November 8th, 2009 [November 8th, 2009]
- Pray this doesn’t get passed | Bad Astronomy - November 8th, 2009 [November 8th, 2009]
- You Can’t Make This Stuff Up | Cosmic Variance - November 8th, 2009 [November 8th, 2009]
- Mother Tongue, Indeed: Newborn’s Cries Mimic Mama’s Accent | 80beats - November 8th, 2009 [November 8th, 2009]
- Ripped From the Journals: The Biggest Discoveries of the Week | 80beats - November 8th, 2009 [November 8th, 2009]
- Alternative Landscapes | The Loom - November 8th, 2009 [November 8th, 2009]
- Can an iPhone App Decipher Your Baby’s Cries? | Discoblog - November 8th, 2009 [November 8th, 2009]
- Reminder: Carl Sagan Day | Bad Astronomy - November 8th, 2009 [November 8th, 2009]
- Are There Pesticides in Your Soup? Dunk a Pollution Dipstick to Find Out. | 80beats - November 8th, 2009 [November 8th, 2009]
- Log in and Join the Conference - November 8th, 2009 [November 8th, 2009]
- Conference Ends - November 8th, 2009 [November 8th, 2009]
- Conference Archive Opens - November 8th, 2009 [November 8th, 2009]
- Galaxy Zoo - November 8th, 2009 [November 8th, 2009]
- .Astronomy 2009 Dates - November 8th, 2009 [November 8th, 2009]
- .Astronomy 2009: Programme and venue details - November 8th, 2009 [November 8th, 2009]
- .Astronomy Gets Some IYA Love - November 8th, 2009 [November 8th, 2009]
- 2009 Posters and Imagery - November 8th, 2009 [November 8th, 2009]
- 2009 Sponsors - November 8th, 2009 [November 8th, 2009]
- When in Holland… - November 8th, 2009 [November 8th, 2009]
- The WHAT Cloud? - November 8th, 2009 [November 8th, 2009]
- The Jewel Box - November 8th, 2009 [November 8th, 2009]
- Happy Halloween! - November 8th, 2009 [November 8th, 2009]
- Ares 1-X Launch - November 8th, 2009 [November 8th, 2009]
- Confessions of an Alien Hunter - November 8th, 2009 [November 8th, 2009]
- LRO Spies Apollo 17 Site - November 8th, 2009 [November 8th, 2009]
- Mercury in Color - November 8th, 2009 [November 8th, 2009]
- Hubble and M83 - November 8th, 2009 [November 8th, 2009]
- Cassini Flyby of Enceladus - November 8th, 2009 [November 8th, 2009]
- Preserving A Moth [Science Tattoo] | The Loom - December 12th, 2009 [December 12th, 2009]
- Another Russian rocket spiral lights up the sky | Bad Astronomy - December 12th, 2009 [December 12th, 2009]
- A (Very Gentle) Riddle to Complete Your Saturday - December 12th, 2009 [December 12th, 2009]
- Darwin Gets Swine Flu: The YouTube Edition | The Loom - December 12th, 2009 [December 12th, 2009]
- Happy Slothy Holidays | The Loom - December 12th, 2009 [December 12th, 2009]
- Jetting to Copenhagen | The Intersection - December 12th, 2009 [December 12th, 2009]
- Michael Gerson Attempts Thoughtfulness on “ClimateGate,” Then Gives it Up | The Intersection - December 13th, 2009 [December 13th, 2009]
- Incredible VISTA of the cosmos | Bad Astronomy - December 13th, 2009 [December 13th, 2009]
- Bundle up Sunday Night to Watch the Geminid Meteor Shower | 80beats - December 13th, 2009 [December 13th, 2009]
- “ClimateGate” a PR Disaster That Will Be “Taught in University Communications Courses” | The Intersection - December 13th, 2009 [December 13th, 2009]
- Is Google the Guardian Angel of Rainforests? | 80beats - December 13th, 2009 [December 13th, 2009]
- La ciencia es importante. Una vez mas. | Bad Astronomy - December 13th, 2009 [December 13th, 2009]
- Sensenbrenner Pulls an Inhofe, Asserts Global Warming is an “International Conspiracy” | The Intersection - December 13th, 2009 [December 13th, 2009]
- Let Kids Eat Dirt: Over-Cleanliness Linked to Heart Disease | 80beats - December 13th, 2009 [December 13th, 2009]
- What Are The Best Science Papers Of The Past Decade? | The Intersection - December 13th, 2009 [December 13th, 2009]
- Finally! Math Shows How to Cut Evenly Sized Pizza Slices | Discoblog - December 13th, 2009 [December 13th, 2009]
- Half-baked math | Bad Astronomy - December 13th, 2009 [December 13th, 2009]
- Can “Biological Passports” Save Sports From Doping? | 80beats - December 13th, 2009 [December 13th, 2009]
- Aiiiieeee! Slow down! | Bad Astronomy - December 13th, 2009 [December 13th, 2009]
- Weekly News Roundup: Bad Headlines, Martian moons, and Rotating Houses | Discoblog - December 13th, 2009 [December 13th, 2009]