Wednesday August 15, 2018

NASA’s Juno spacecraft to make its Fifth flyby over Jupiter’s mysterious Cloud Tops

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Jupiter, Source: NASA
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Washington, March 26, 2017: NASA said its Juno spacecraft will make its fifth flyby over Jupiter’s mysterious cloud tops on Monday.

At the time of closest approach, Juno will be about 4,400 km above the planet’s cloud tops, moving at a speed of about 57.8 km per second relative to the gas-giant planet.

All of Juno’s eight science instruments will be on and collecting data during the flyby.

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“This will be our fourth science pass — the fifth close flyby of Jupiter of the mission — and we are excited to see what new discoveries Juno will reveal,” said Scott Bolton, Principal Investigator of Juno from the Southwest Research Institute in San Antonio, US.

“Every time we get near Jupiter’s cloud tops, we learn new insights that help us understand this amazing giant planet,” Bolton said in a statement.

Launched on August 5, 2011, from Cape Canaveral, Florida, Juno arrived in orbit around Jupiter on July 4, 2016.

During its mission of exploration, Juno soars low over the planet’s cloud tops.

During these flybys, Juno probes beneath the obscuring cloud cover of Jupiter and studying its auroras to learn more about the planet’s origins, structure, atmosphere and magnetosphere.

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The Juno science team continues to analyse returns from previous flybys. Scientists have discovered that Jupiter’s magnetic fields are more complicated than originally thought, and that the belts and zones that give the planet’s cloud tops their distinctive look extend deep into the its interior.

Observations of the energetic particles that create the incandescent auroras suggest a complicated current system involving charged material lofted from volcanoes on Jupiter’s moon Io.

Peer-reviewed papers with more in-depth science results from Juno’s first flybys are expected to be published within the next few months, NASA said. (IANS)

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The Secret Behind NASA’s Parker Solar Probe

The spacecraft, launched from Cape Canaveral Air Force Station in Florida on August 12, will transmit its first scientific observations in December.

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Why won't NASA's Parker Solar Probe melt?
Why won't NASA's Parker Solar Probe melt?VOA

With NASA launching a historic Parker Solar Probe deeper into the solar atmosphere than any mission before it, a moot question arises: Why won’t it melt?

Inside the solar atmosphere — a region known as the corona — the probe will provide observations of what drives the wide range of particles, energy and heat that course through the region.

The spacecraft will travel through material with temperatures greater than several million degrees Celsius while being bombarded with intense sunlight.

According to the US space agency, Parker Solar Probe has been designed to withstand the extreme conditions and temperature fluctuations for the mission.

“The key lies in its custom heat shield and an autonomous system that helps protect the mission from the Sun’s intense light emission, but does allow the coronal material to ‘touch’ the spacecraft,” NASA said in a statement.

Parker solar probe
The spacecraft, launched from Cape Canaveral Air Force Station. IANS

While the Parker Solar Probe will travel through a space with temperatures of several million degrees, the surface of the heat shield that faces the Sun will only get heated to about 1,400 degree Celsius.

This is because “in space, the temperature can be thousands of degrees without providing significant heat to a given object or feeling hot. Since space is mostly empty, there are very few particles that can transfer energy to the spacecraft”.

The corona through which the Parker Solar Probe flies, for example, has an extremely high temperature but very low density.

The probe makes use of a heat shield known as the Thermal Protection System, or TPS, which is eight feet in diameter and 4.5 inches thick.

Those few inches of protection mean that just on the other side of the shield, the spacecraft body will sit at a comfortable 30 degrees Celsius.

Parker-Solar-2, NASA
The Parker Solar Probe sits in a clean room at Astrotech Space Operations in Titusville, Fla., after the installation of its heat shield. VOA

The TPS was designed by the Johns Hopkins Applied Physics Laboratory, and was built at Carbon-Carbon Advanced Technologies, using a carbon composite foam sandwiched between two carbon plates.

This lightweight insulation will be accompanied by a finishing touch of white ceramic paint on the sun-facing plate, to reflect as much heat as possible.

“Tested to withstand up to 1,650 degrees Celsius, the TPS can handle any heat the Sun can send its way, keeping almost all instrumentation safe,” said NASA.

Another challenge came in the form of the electronic wiring — most cables would melt from exposure to heat radiation at such close proximity to the Sun.

To solve this problem, the team grew sapphire crystal tubes to suspend the wiring, and made the wires from the chemical element niobium.

NASA
Several other designs on the spacecraft keep Parker Solar Probe sheltered from the heat.Flickr

Several other designs on the spacecraft keep Parker Solar Probe sheltered from the heat.

Without protection, the solar panels — which use energy from the very star being studied to power the spacecraft — can overheat.

At each approach to the Sun, the solar arrays retract behind the heat shield’s shadow, leaving only a small segment exposed to the Sun’s intense rays.

Also Read: Red-hot Voyage to Sun Will Bring us Closer to our Star

The solar arrays have a surprisingly simple cooling system: a heated tank that keeps the coolant from freezing during launch, two radiators that will keep the coolant from freezing, aluminium fins to maximise the cooling surface, and pumps to circulate the coolant.

The spacecraft, launched from Cape Canaveral Air Force Station in Florida on August 12, will transmit its first scientific observations in December. (IANS)