NASA Maneuvers Juno Spacecraft To Avoid Unusual Death

The Jovian south pole. NASA/JPL-Caltech/SwRI/MSSS 

Space is fraught with dangers and the engineers and scientists working on space missions need to anticipate them and be able to deal with many complex situations. NASA’s Juno recently had to conduct a propulsive maneuver to change its orbital velocity by 203 kilometers (126 miles) per hour.

This was deemed necessary as the spacecraft was risking death by eclipse. Now, this is an unusual cause of death even for space standards. We have smashed probes into planets by accident and on purpose, and even just plain lost them, but the eclipse is peculiar. The issue is that Jupiter is huge and Juno is solar-powered. Not an ideal combo in certain circumstances.

And on November 3, the craft was going to transit Jupiter’s shadow for 12 hours. That's long enough for Juno’s battery to be completely drained. With no power and in the cold of space, the craft was unlikely to survive. For this reason, between September 30 and October 1, NASA burned 73 kilograms (160 pounds) of fuel to carry out a 10.5-hour propulsive maneuver. This is five times longer than any previous use of the reaction-control thruster.

"With the success of this burn, we are on track to jump the shadow on Nov. 3," Scott Bolton, Juno principal investigator at the Southwest Research Institute in San Antonio, said in a statement. "Jumping over the shadow was an amazingly creative solution to what seemed like a fatal geometry. Eclipses are generally not friends of solar-powered spacecraft. Now instead of worrying about freezing to death, I am looking forward to the next science discovery that Jupiter has in store for Juno."

Animated view of what Juno will see approaching Jupiter on November 3. The Sun (yellow dot to the left) is no longer obscured. NASA/JPL-Caltech/SWRI

Juno arrived at Jupiter in 2016. It performs a close flyby every 53 days with the next one happening on November 3. It will be its 23rd close flyby, taking it to an altitude of just 4,200 kilometers (2,600 miles) from the clouds of Jupiter. The mission has collected incredible data about the gas giant planet while also capturing breathtaking views. In June 2018, the mission was extended for another three years. 

"Pre-launch mission planning did not anticipate a lengthy eclipse that would plunge our solar-powered spacecraft into darkness," explained Ed Hirst, Juno project manager at NASA's Jet Propulsion Laboratory in Pasadena, California. "That we could plan and execute the necessary maneuver while operating in Jupiter's orbit is a testament to the ingenuity and skill of our team, along with the extraordinary capability and versatility of our spacecraft."

There are now 35 planned flybys, with the last one set to be on July 30, 2021. At that point, the craft will indeed be dead but in fire not in ice. The craft will be plunged into Jupiter to avoid any possible contamination of the Jovian system.


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