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No Picnic in the Clouds! It’s JPL aerobot

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JPL’s Venus Aerial Robotic Balloon Prototype Aces Test Flights

A scaled-down version of the aerobot that could one day take to the Venusian skies successfully completed two Nevada test flights, marking a milestone for the project.

The intense pressure, heat, and corrosive gases of Venus’ surface are enough to disable even the most robust spacecraft in a matter of hours. But a few dozen miles overhead, the thick atmosphere is far more hospitable to robotic exploration.

One concept envisions pairing a balloon with a Venus orbiter, the two working in tandem to study Earth’s sister planet. While the orbiter would remain far above the atmosphere, taking science measurements and serving as a communication relay, an aerial robotic balloon, or aerobot, about 40 feet (12 meters) in diameter would travel into it.

To test this concept, a team of scientists and engineers from NASA’s Jet Propulsion Laboratory in Southern California and the Near Space Corporation in Tillamook, Oregon, recently carried out two successful flights of a prototype balloon that’s about a third of that size.

The shimmering silver balloon ascended more than 4,000 feet (1 kilometer) over Nevada’s Black Rock Desert to a region of Earth’s atmosphere that approximates the temperature and density the aerobot would experience about 180,000 feet (55 kilometers) above Venus. Coordinated by Near Space, these tests represent a milestone in proving the concept’s suitability for accessing a region of Venus’ atmosphere too low for orbiters to reach, but where a balloon mission could operate for weeks or even months.

JPL’s Venus Aerobot Prototype Aces Test Flights Over Nevada

“We’re extremely happy with the performance of the prototype. It was launched, demonstrated controlled-altitude maneuvers, and was recovered in good condition after both flights,” said robotics technologist Jacob Izraelevitz, who leads the balloon development as the JPL principal investigator of the flight tests. “We’ve recorded a mountain of data from these flights and are looking forward to using it to improve our simulation models before exploring our sister planet.”

The only balloon-borne exploration of Venus’ atmosphere to date was a part of the twin Soviet Vega 1 and 2 missions that arrived at the planet in 1985. The two balloons (which were about 11.5 feet, or 3.6 meters, in diameter when filled with helium) lasted a little over 46 hours before their instruments’ batteries ran out. Their short time in the Venusian atmosphere provided a tantalizing hint of the science that could be achieved by a larger, longer-duration balloon platform floating within the planet’s atmosphere.

A prototype aerial robotic balloon, or aerobot, is readied for a sunrise test flight at Black Rock Desert, Nevada, in July 2022, by team members from JPL and Near Space Corporation. The aerobot successfully completed two flights, demonstrating controlled altitude flight. Credit: NASA/JPL-Caltech

‘Roving’ the Skies

The ultimate goal of the aerobot would be to travel on the Venusian winds, floating from east to west, circumnavigating the planet for at least 100 days. The aerobot would serve as a platform for a range of science investigations, from monitoring the atmosphere for acoustic waves generated by venusquakes to analyzing the chemical composition of the clouds. The accompanying orbiter would receive data from the aerobot and relay it to Earth while providing a global view of the planet.

Much like a Mars rover is commanded to drive to an interesting rock or other feature, the aerobot can be directed to raise and lower its altitude – something the Vega balloons couldn’t do – to conduct science between about 171,000 and 203,000 feet (52 and 62 kilometers) within Venus’ atmosphere.

The prototype balloon was fabricated using Near Space’s techniques for performance aerospace inflatables. Designed as a “balloon within a balloon,” it has a rigid inner reservoir filled with helium under high pressure and an encapsulating outer helium balloon that can expand and contract. To increase altitude, helium vents from the inner reservoir into the outer balloon, which expands to give the aerobot additional buoyancy. When it’s time to reduce altitude, helium is pumped back into the reservoir, causing the outer balloon to shrink and decrease the aerobot’s buoyancy.

“The success of these test flights is a huge deal for us: We’ve successfully demonstrated the technology we’ll need for investigating the clouds of Venus,” said Paul Byrne, an associate professor at Washington University in St. Louis and aerobot science collaborator. “These tests form the foundation for how we can achieve long-term robotic exploration high above Venus’ hellish surface.”

The one-third scale prototype aerobot is designed to withstand the corrosive chemicals in Venus’ atmosphere. During the flights, the balloon’s materials were tested for the first time, giving the team confidence that a larger aerobot design could operate in Venus skies. Credit: Near Space Corporation

No Picnic in the Clouds

While this region of Venus’ atmosphere is more forgiving than its lower reaches, long-duration flights in the rocky planet’s clouds, which contain sulfuric acid and other corrosive chemicals, would be no picnic. So the multilayered material developed for the aerobot’s outer balloon includes an acid-proof coating, a metallization layer to reduce solar heating, and a structural inner layer that keeps it strong enough to carry the science instruments below. New techniques have also been developed to ensure a long-duration acid-proof seal with minimal helium leakage from the seams.

“The materials being used for Venus survivability are challenging to fabricate with, and the robustness of handling we’ve demonstrated in the Nevada launch and recovery gives us confidence for balloon’s reliability on Venus,” said co-investigator Tim Lachenmeier, chief executive officer of Near Space.

While the recent Nevada tests were a milestone for a future concept designed with Venus in mind, the researchers say the technology could also be used by high-altitude science balloons that need to control their altitude in Earth’s skies.

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Astronomers Detect Protective Shield Defending Pair of ‘Dwarf Galaxies’ with help of FUSE, Hubble

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For billions of years, the Milky Way’s largest satellite galaxies – the Large and Small Magellanic Clouds – have followed a perilous journey. Orbiting one another as they are pulled in toward our home galaxy, they have begun to unravel, leaving behind trails of gaseous debris. And yet – to the puzzlement of astronomers – these dwarf galaxies remain intact, with ongoing vigorous star formation.

“A lot of people were struggling to explain how these streams of material could be there,” said Dhanesh Krishnarao, assistant professor at Colorado College. “If this gas was removed from these galaxies, how are they still forming stars?”

With the help of data from NASA’s Hubble Space Telescope and a retired satellite called the Far Ultraviolet Spectroscopic Explorer (FUSE), a team of astronomers led by Krishnarao has finally found the answer: the Magellanic system is surrounded by a corona, a protective shield of hot supercharged gas. This cocoons the two galaxies, preventing their gas supplies from being siphoned off by the Milky Way, and therefore allowing them to continue forming new stars.

Description of the above image:

Researchers have used spectroscopic observations of ultraviolet light from quasars to detect and map out the Magellanic Corona, a diffuse halo of hot, supercharged gas surrounding the Small and Large Magellanic Clouds. Shown here in purple, the corona stretches more than 100,000 light-years from the main mass of stars, gas, and dust that make up the Magellanic Clouds, intermingling with the hotter and more extensive corona that surrounds the Milky Way. The Magellanic Clouds, dwarf galaxies roughly 160,000 light-years from Earth, are the largest of the Milky Way’s satellites and are thought to be on their first in-falling passage around the Milky Way. This journey has begun to unravel what were once barred spirals with multiple arms into more irregular-shaped galaxies with long tails of debris. The corona is thought to act as a buffer protecting the dwarf galaxies’ vital star-forming gas from the gravitational pull of the much larger Milky Way. The detection of the Magellanic Corona was made by analyzing patterns in ultraviolet light from 28 distant background quasars. As the quasar light passes through the corona, certain wavelengths (colors) of ultraviolet light are absorbed. The quasar spectra become imprinted with the distinct signatures of carbon, oxygen, and silicon ions that make up the corona gas. Because each quasar probes a different part of the corona, the research team was also able to show that the amount of gas decreases with distance from the center of the Large Magellanic Cloud. This study used archival observations of quasars from Hubble’s Cosmic Origins Spectrograph (COS) and the Far Ultraviolet Spectroscopic Explorer (FUSE). Quasars have also been used to probe the Magellanic Stream, outflows from the Milky Way , and the halo surrounding the Andromeda Galaxy./Illustration Credits: STScI, Leah Hustak

 

This discovery, which was just published in Nature, addresses a novel aspect of galaxy evolution. “Galaxies envelope themselves in gaseous cocoons, which act as defensive shields against other galaxies,” said co-investigator Andrew Fox of the Space Telescope Science Institute in Baltimore, Maryland.

Astronomers predicted the corona’s existence several years ago. “We discovered that if we included a corona in the simulations of the Magellanic Clouds falling onto the Milky Way, we could explain the mass of extracted gas for the first time,” explained Elena D’Onghia, a co-investigator at the University of Wisconsin–Madison. “We knew that the Large Magellanic Cloud should be massive enough to have a corona.”

But although the corona stretches more than 100,000 light-years from the Magellanic clouds and covers a huge portion of the southern sky, it is effectively invisible. Mapping it out required scouring through 30 years of archived data for suitable measurements.

Researchers think that a galaxy’s corona is a remnant of the primordial cloud of gas that collapsed to form the galaxy billions of years ago. Although coronas have been seen around more distant dwarf galaxies, astronomers had never before been able to probe one in as much detail as this.

There’re lots of predictions from computer simulations about what they should look like, how they should interact over billions of years, but observationally we can’t really test most of them because dwarf galaxies are typically just too hard to detect,” said Krishnarao. Because they are right on our doorstep, the Magellanic Clouds provide an ideal opportunity to study how dwarf galaxies interact and evolve.

In search of direct evidence of the Magellanic Corona, the team combed through the Hubble and FUSE archives for ultraviolet observations of quasars located billions of light-years behind it. Quasars are the extremely bright cores of galaxies harboring massive active black holes. The team reasoned that although the corona would be too dim to see on its own, it should be visible as a sort of fog obscuring and absorbing distinct patterns of bright light from quasars in the background. Hubble observations of quasars were used in the past to map the corona surrounding the Andromeda galaxy.

By analyzing patterns in ultraviolet light from 28 quasars, the team was able to detect and characterize the material surrounding the Large Magellanic Cloud and confirm that the corona exists. As predicted, the quasar spectra are imprinted with the distinct signatures of carbon, oxygen, and silicon that make up the halo of hot plasma that surrounds the galaxy.

The ability to detect the corona required extremely detailed ultraviolet spectra. “The resolution of Hubble and FUSE were crucial for this study,” explained Krishnarao. “The corona gas is so diffuse, it’s barely even there.” In addition, it is mixed with other gases, including the streams pulled from the Magellanic Clouds and material originating in the Milky Way.

By mapping the results, the team also discovered that the amount of gas decreases with distance from the center of the Large Magellanic Cloud. “It’s a perfect telltale signature that this corona is really there,” said Krishnarao. “It really is cocooning the galaxy and protecting it.”

How can such a thin shroud of gas protect a galaxy from destruction?

“Anything that tries to pass into the galaxy has to pass through this material first, so it can absorb some of that impact,” explained Krishnarao. “In addition, the corona is the first material that can be extracted. While giving up a little bit of the corona, you’re protecting the gas that’s inside of the galaxy itself and able to form new stars.”