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article imageSticky valves cause of Juno spacecraft's longer orbit of Jupiter

By Karen Graham     Feb 26, 2017 in Science
On Thursday, NASA announced its Juno spacecraft circling the giant gas planet, Jupiter, would remain in its 53-day orbit pattern, instead of dropping to a planned 14-day pattern, for the remainder of its mission. NASA blames sticky valves.
The original Juno flight plan envisioned the spacecraft looping around Jupiter twice in 53-day orbits, then reducing its orbital period to 14 days for the remainder of the mission. But after a number of delays, ABC News reports that NASA decided to scrap a planned engine firing that would have shortened the orbit.
Two helium check valves that are part of the plumbing for the spacecraft’s main engine did not operate as expected when the propulsion system was pressurized in October 2016. NASA says telemetry from the spacecraft indicated that it took several minutes for the valves to open, while it took only a few seconds during past main engine firings.
NASA's Juno Mission
Juno has been in orbit around Jupiter since July 4, 2016, after being launched from Cape Canaveral, Florida in 2011, The spacecraft's arrival was the culmination of a journey that covered 1.7 billion miles (2.7 billion kilometers).
“During a thorough review, we looked at multiple scenarios that would place Juno in a shorter period orbit, but there was concern that another main engine burn could result in a less-than-desirable orbit,” said Rick Nybakken, Juno project manager at NASA’s Jet Propulsion Laboratory in Pasadena, California. “The bottom line is a burn represented a risk to completion of Juno’s science objectives.”
NASA's Juno Mission
Actually, the longer orbit is not going to affect the quality of the science being sent back or the quality of the stunning images of Jupiter. They will keep coming but it will take a little longer for scientists to receive them. explains that if the mission is to be completed as originally planned, and based on the longer orbit Juno is stuck in, it will cost tens of millions of extra dollars.
There is a plus side to the sticky valve situation, though. Juno will spend less time in Jupiter's radiation belts. "Jupiter has the scariest radiation environment of any planet in the solar system," Heidi Becker, leader of Juno’s radiation-monitoring team said in July last year. "It's the harshest, it's the most intense and it hasn't been fully explored yet — and it hasn't been fully explored where we're going."
With every orbit, Juno flies within 2,600 miles (4,200 kilometers) of Jupiter's cloud tops. The last completed orbit was three weeks ago and the next flyby will come at the end of March. When Juno's mission is completed, it will die a fiery death plunging into Jupiter's atmosphere, burning up, meteor-style.
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