Juno Spacecraft Faced Challenges During Recent Jupiter Approach

A composite image of Jupiter’s cloud formations as seen through the eyes of Juno’s Microwave Radiometer, which can see up to 250 miles into the planet's atmosphere with its largest antenna. The belts and bands visible on the surface are also visible in modified form in each layer below. Image credit: NASA/JPL-Caltech/SwRI/GSFC

 
Last week, NASA's Juno spacecraft reached perijove, the closest point of its 53.5-day orbit around Jupiter, when it passed less than 3000 miles from the gas giant's clouds. But during its approach, the onboard computer suddenly detected an unexpected condition and turned off unnecessary subsystems, entering “safe mode.” The solar-powered spacecraft then went "power positive," shutting down the cameras and reorienting itself toward the Sun, where it linked up with the Deep Space Network back on Earth. Then it waited for humans to evaluate the situation and provide guidance.

It was a disappointing outcome for the Southwest Research Institute scientists leading the mission, including principal investigator Scott Bolton. Because the science instruments were shut down during the flyby, no data were collected. But this outcome was also a necessary one. In space, power is king. Engineers can often fix—or find inventive workarounds to—problems of enormous complexity, even from hundreds of millions of miles away. The one thing that is non-negotiable, however, is power. The spacecraft must be alive to receive commands. So in this case, "safe mode" is a good thing—the robot did exactly what it was supposed to do in this situation.

According to the original plan, the October 19 maneuver was not meant to be a science orbit, but rather, a "period reduction maneuver." The Juno team initially intended to fire the same rocket motor that performed the daring insertion maneuver on July 4, when it purposefully slowed its engines enough to be caught by Juno’s gravity and orbit the poles. If successful, last week's rocket firing would have slowed the spacecraft and changed its orbit from 53.5 days to two weeks.

While preparing for the maneuver, however, the team noticed that the valves in the spacecraft's propulsion system were behaving sluggishly, as though the valves were "sticky." Rather than take any chances with the spacecraft's delicate orbit, they decided to postpone the maneuver and switch on the science instruments instead, making this a science pass.

The scientific investigation of Jupiter is tied to a two-hour window every orbit when the spacecraft reaches perijove. During that time, the spacecraft travels from Jupiter's north pole to its south. Whether it makes this traversal following a 14-day orbit or roughly 7.5-week orbit makes no difference at all; the current longer orbit simply means it will take longer to reach the completion of the mission.

Then the plan for a science pass fell through too when the spacecraft switched into safe mode.

Although these are two disappointing events in a row, everything will be okay, Bolton said at a press event during the 2016 meeting of the American Astronomical Society's Division for Planetary Sciences. The team can still fire the rocket in the future. Until then, they will work to determine what caused the safe mode and why the valves were behaving oddly. Bolton explained that the team is in no rush. "Fortunately, the way we designed Juno, and the orbit we went into, is very flexible," he said. "It allows very flexible science."

Though this flyby was a wash, a previous, successful flyby on August 27 has yielded extraordinary science. Then, an instrument called a microwave radiometer peered into Jupiter's atmosphere, giving scientists the first-ever look beneath the planet's clouds. Peeling away layers of the atmosphere as though it were an onion and looking as deeply within as 250 miles, scientists discovered that the atmosphere retains the famous structure of the zones and belts of clouds visible from telescopes.

"Whatever is making those colors—whatever is making those stripes—is still existing pretty far down into Jupiter," Bolton said. "That came as a surprise to many of the scientists. We didn't know if [Jupiter's appearance] was skin deep—just a very thin layer—or whether it goes down." Another surprise was that the colorful zones and belts also appear to evolve and change at various depths. This hints at the deep dynamics and chemistry of Jupiter's atmosphere, though the details still require much analysis.

NASA/JPL-Caltech/SwRI/MSSS/Alex Mai

 
During that same pass, Juno's camera captured images as the spacecraft crossed the "terminator" of Jupiter—that is, the line between the sunlit side of the planet and the side in darkness. Think of a half-moon: The terminator is the line where the bright half meets the dark half.

The above image of the sunlit half was created by citizen scientist Alex Mai using data from the spacecraft's JunoCam instrument. (Raw images from the mission are available at JunoCam for both public and professional use.) Meanwhile, the shadows revealed the topology of Jupiter's atmosphere—another first. A particularly pronounced feature was a cyclone raging even above Jupiter's base atmosphere. It's 53 miles tall and 4350 miles wide—half the size of the Earth.

"Imagine the kind of atmosphere you're dealing with," marveled Bolton.

For now, scientists will need to imagine a little longer. Juno's next flyby of Jupiter will be on December 11.

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NASA Has a Plan to Stop the Next Asteroid That Threatens Life on Earth
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iStock

An asteroid colliding catastrophically with Earth within your lifetime is unlikely, but not out of the question. According to NASA, objects large enough to threaten civilization hit the planet once every few million years or so. Fortunately, NASA has a plan for dealing with the next big one when it does arrive, Forbes reports.

According to the National Near-Earth Object Preparedness Strategy and Action Plan [PDF] released by the White House on June 21, there are a few ways to handle an asteroid. The first is using a gravity tractor to pull it from its collision course. It may sound like something out of science fiction, but a gravity tractor would simply be a large spacecraft flying beside the asteroid and using its gravitational pull to nudge it one way or the other.

Another option would be to fly the spacecraft straight into the asteroid: The impact would hopefully be enough to alter the object's speed and trajectory. And if the asteroid is too massive to be stopped by a spacecraft, the final option is to go nuclear. A vehicle carrying a nuclear device would be launched at the space rock with the goal of either sending it in a different direction or breaking it up into smaller pieces.

Around 2021, NASA will test its plan to deflect an asteroid using a spacecraft, but even the most foolproof defense strategy will be worthless if we don’t see the asteroid coming. For that reason, the U.S. government will also be working on improving Near-Earth Object (NEO) detection, the technology NASA uses to track asteroids. About 1500 NEOs are already detected each year, and thankfully, most of them go completely unnoticed by the public.

[h/t Forbes]

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Frederick M. Brown, Getty Images
Stephen Hawking’s Memorial Will Beam His Words Toward the Nearest Black Hole
Frederick M. Brown, Getty Images
Frederick M. Brown, Getty Images

An upcoming memorial for Stephen Hawking is going to be out of this world. The late physicist’s words, set to music, will be broadcast by satellite toward the nearest black hole during a June 15 service in the UK, the BBC reports.

During his lifetime, Hawking signed up to travel to space on Richard Branson’s Virgin Galactic spaceship, but he died before he ever got the chance. (He passed away in March.) Hawking’s daughter Lucy told the BBC that the memorial's musical tribute is a “beautiful and symbolic gesture that creates a link between our father's presence on this planet, his wish to go into space, and his explorations of the universe in his mind.” She described it as "a message of peace and hope, about unity and the need for us to live together in harmony on this planet."

Titled “The Stephen Hawking Tribute,” the music was written by Greek composer Vangelis, who created the scores for Blade Runner and Chariots of Fire. It will play while Hawking’s ashes are interred at Westminster Abbey, near where Isaac Newton and Charles Darwin are buried, according to Cambridge News. After the service, the piece will be beamed into space from the European Space Agency’s Cebreros Station in Spain. The target is a black hole called 1A 0620-00, “which lives in a binary system with a fairly ordinary orange dwarf star,” according to Lucy Hawking.

Hawking wasn't the first person to predict the existence of black holes (Albert Einstein's general theory of relativity accounted for them back in the early 1900s), but he spoke at length about them throughout his career and devised mathematical theorems that gave credence to their existence in the universe.

Actor Benedict Cumberbatch, a friend of the Hawking family who portrayed the late scientist in the BBC film Hawking, will speak at the service. In addition to Hawking's close friends and family, British astronaut Tim Peake and several local students with disabilities have also been invited to attend.

[h/t BBC]

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