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Scientists on edge awaiting Juno’s perilous encounter with Jupiter

Credit: NASA/JPL-Caltech
This artist’s concept shows Juno’s approach path toward Jupiter for the July 4 insertion maneuver. Jupiter’s intense radiation belts are also illustrated here. Credit: NASA/JPL-Caltech

Speeding toward Jupiter at nearly 40 miles per second, NASA’s Juno spacecraft must brave a field of computer-zapping radiation and Jupiter’s tenuous ring of ice and dust particles when it brakes into orbit around the planet Monday and zooms just 2,900 miles from the world’s turbulent cloud tops.

That may sound far, but it is 10 times closer than any previous missions, other than probes doomed to destruction sent into the atmosphere.

The perils give pause to scientists and engineers working on the $1.1 billion mission, but officials said they did everything possible to equip Juno for the dangers of Jupiter and were cautiously optimistic the probe would complete a one-shot orbit insertion maneuver unscathed.

“Juno is going to go into the scariest part of the scariest place that we know about,” said Heidi Becker, a physicist at NASA’s Jet Propulsion Laboratory in Pasadena, California.

Radiation belts surround Jupiter’s equator, where the planet’s strong magnetic field trap high-energy particles and accelerate them to nearly light-speed, posing a hazard to Juno unparalleled to any environment ever directly explored by a human-built spacecraft.

“Jupiter’s magnetic field has accelerated them to the point where they will go right through a spacecraft and strip the atoms apart inside your electronics and fry your brain if you don’t do anything about it, so we did a lot about it,” Becker said.

The most critical electronic components aboard Juno are housed inside a vault with walls of pure titanium a third of an inch (1 centimeter) thick. Engineers expect the protective box, which measures about the size of an SUV’s trunk, will block most of the dangerous particles from penetrating into Juno’s sensitive computers and triggering a reset, or worse.

“It’s where we protect our valuables,” said Rick Nybakken, Juno’s project manager at JPL.

Jupiter’s magnetosphere, a bubble around the planet under the influence of its magnetic field, extends out 10 times farther than the magnetosphere around Earth. Juno crossed the magnetosphere’s bow shock, a boundary between interplanetary space where the solar wind is dominant and Jupiter’s magnetic field, about 10 days ago as it zoomed toward its rendezvous with the planet.

If it was visible in the night sky from Earth, it would appear as big as the moon, scientists said.

Juno’s three huge rectangular solar panels, arranged in a triangle configuration like an airplane’s propeller, stretch 30 feet (9 meters) long and contain 18,698 solar cells to generate electricity. At Jupiter’s distance a half-billion miles from the sun, where the cells receive about 4 percent of the solar energy as they did at Earth, the wings produce a mere 500 watts, equivalent to around five household light bulbs.

The solar panels are also sensitive to radiation, so engineers added extra-thick cover glass to the each cell.

Juno is also targeting a section of space near Jupiter that may harbor scattered particles of ice and dust from the gas giant’s narrow ring system, according to Scott Bolton, the mission’s principal investigator from the Southwest Research Institute in San Antonio.

Discovered in 1979 by NASA’s Voyager 1 flyby probe, the rings of Jupiter contain flakes of ice and dust — tiny frozen moonlets — deposited around the planet by meteoroid impacts on Jupiter’s larger moons.

This image of Jupiter's rings came from NASA's Galileo mission, which became the first spacecraft to orbit the planet. Galileo explored Jupiter and its moons from 1995 through 2003. Credit: NASA, JPL, Galileo Project, (NOAO), J. Burns (Cornell) et al.
This image of Jupiter’s rings came from NASA’s Galileo mission, which became the first spacecraft to orbit the planet. Galileo explored Jupiter and its moons from 1995 through 2003. Credit: NASA, JPL, Galileo Project, (NOAO), J. Burns (Cornell) et al.

“Theres a vertical excent of these rings that isn’t very well known,” Bolton said Monday. “Juno has to pass through these rings. We do not know how close to the planet they actually go, and if it gets hit even by a small piece of dust, it can do very serious damage.”

Juno’s Leros 1b main engine is supposed to ignite for 35 minutes Monday to put the spacecraft into an elliptical 53.5-day orbit around Jupiter. Engineers aid the engine must fire for at least 20 minutes to achieve any safe orbit, or Juno will cruise past Jupiter and the mission will be lost.

Ground controllers sent commands for Juno to open an engine cover June 20 in advance of Monday’s firing, and the celestial mechanics of the burn require the engine nozzle to point ahead of the spacecraft directly into any potential incoming debris at a speed of 130,000 mph (209,000 kilometers per hour), relative to Jupiter.

“The nozzle is open and vulnerable,” Bolton said. “We’re flying through faster than any object has ever gone with the nozzle facing forward. If any dust is in our way and hits that nozzle, it will knock a hole right through the coating that protects the nozzle and allows the engine to burn uninterrupted. So thats one of the big gambles.”

Juno will repeat Monday’s close brush by Jupiter 36 more times before its mission is complete Feb. 20, 2018, when the craft will head toward a crushing dive into the atmosphere.

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Follow Stephen Clark on Twitter: @StephenClark1.

Source: You’ll find lots of information about the planets Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Also we have facts about the space station, ISS, SpaceX launch, space program, and outerspace. Space Flight

Scientists on edge awaiting Juno’s perilous encounter with Jupiter

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