New Space Telescopes Could Look Like Giant Beach Balls

Inflatable balloon reflectors could peer into deep space, scanning for signs of water, at a fraction of the cost of a traditional telescope.

CHRIS WALKER

https://www.wired.com/story/new-space-telescopes-could-look-like-giant-beach-balls/

IF WE EVER have giant inflatable telescopes in space, you can thank Chris Walker’s mom. Years ago, Walker was making 

chocolate pudding when he had to interrupt his culinary undertaking to field a phone call from his mother. He took the pudding off the stovetop, covered it with plastic wrap, and placed the pot on the floor by his couch. When the call was finished, he was startled to find an image of a lightbulb from a nearby lamp hovering over the end of the couch. When he investigated the cause of this apparition, he found that a pocket of cold air that formed as the pudding cooled had caused the center of the plastic wrap to sag toward the pudding. This had, in effect, formed a lens that was reflecting the lightbulb.

“I thought, ‘hey, this is cool, but I have no use for it now,’” Walker, a professor of astronomy at the University of Arizona, says. But 30 years later, he used it as the basis for a proposal he sent to NASA Innovative Advanced Concepts, a program that funds far-out aerospace ideas.

The subject of that proposal was essentially a way to turn a giant inflatable beach ball into a space telescope. This suborbital balloon reflector wouldn’t contend with as much atmospheric interference as ground-based telescopes. Furthermore, it could be easily scaled up, thereby opening vasts swaths of the universe to observation without the hefty price tag associated with building large, solid telescopes.

The idea for the large balloon reflector grew out of Walker’s 

work on the Stratospheric Terahertz Observatory, a one-meter telescope attached to a high-altitude balloon that circled Antarctica in the upper atmosphere for several weeks in 2012. As Walker watched the balloon inflate with 35 million cubic feet of helium, it occurred to him that the balloon was a lot of wasted space for such a small telescope. Wouldn’t it be nice if the balloon itself could be used as an observatory? This observation, combined with the insight from the pudding incident decades prior, led to the creation of the first inflatable telescope.

In 2014, Walker and his students made the first prototype of the large balloon reflector out of a large inflatable plastic sphere sold by a Chinese toy manufacturer. The ball had been designed for people to climb around inside like a human-sized “gerbil ball,” but it also turned out to be pretty great for radio astronomy. Walker suspended an antenna inside the ball and sprayed a circle with metallic paint on the inside to create a reflector. With this rudimentary setup, Walker and his students were able to do radio observations of the sun from the rooftop of the astronomy building at the University of Arizona. Even though it wasn’t sent to the upper atmosphere, Walker says it demonstrates that even a very crude version of the telescope could get good results. “I knew it would work, but you have to show people,” he says. “Nothing beats a rooftop demonstration.”

CHRIS WALKER

But Walker realized the real benefits of a spherical, inflatable telescope would be found in space. Traditional radio telescopes use parabolic dishes as reflectors, which gather radiation and focus it on a specific point. While this works well enough, astronomers have to move the entire dish to point it a specific spot, which becomes a burden when the telescope is in space. With Walker’s design, you can point the telescope by moving the antenna inside the sphere, rather than repositioning the entire telescope. A spherical telescope also has a large field of view, so it can image large portions of the universe without moving.

Walker’s inflatable telescope is not the first time NASA has flirted with beach balls in space. In the early 1960s, NASA launched Echo 1 and Echo 2, which were massive inflatable reflectors that could passively bounce radio signals around the world. But no one ever applied the concept to deep space observation. (Although in 1996, NASA did an experiment 

with an inflatable parabolic reflector in space.) After proving that the large balloon reflector worked as intended, Walker received a Phase 2 NIAC grant to design a space-based version of the inflatable telescope.

The result is the Terahertz Space Telescope, an inflatable ball 40 meters in diameter with a steerable antenna inside. Because gas pressure in space is so low, Walker says you could inflate the massive telescope using less gas—likely nitrogen or neon due to their low freezing temperatures—than you’d need to inflate a party balloon on Earth. Obviously space debris and micrometeoroids are a concern for inflatable objects in orbit, but Walker says if one were to hit the balloon, the slow diffusion of gas in the telescope means that it would still take years before the telescope deflated.

The effective diameter of the Terahertz Space Telescope, Walker says, would be about 25 meters. To put this in perspective, the James Webb Space Telescope, which is slated to launch in 2021 and will be the most sensitive telescope ever sent to space, has an aperture of about 6.5 meters. The price difference is even more dramatic: Walker estimates the inflatable telescope would cost about a $200 million to send to orbit, whereas the James Webb telescope is expected to cost about $10 billion by the time it’s launched.

But Walker's telescope still needs to get built. If it can overcome that hurdle, the Terahertz Space Telescope could observe the universe using wavelengths that would allow it to detect the presence of water in deep space. It could help locate water-rich asteroids within our solar system, or help detect water in the habitable zones of other solar systems. Walker is particularly excited about the prospect of detecting gaseous water near the stars in protoplanetary systems, which he says could tell us a great deal about how Earth came to be covered in water.

For now, though, the Terahertz Space Telescope has only undergone two small experimental tests. Both tests were conducted under the auspices of Freefall Aerospace, a company Walker co-founded as a spinoff of his work on inflatable telescopes. Freefall aims to use inflatable satellites similar in design to this telescope to beam 5G to Earth. Last year, a prototype of one of these inflatable satellites hitched a ride to the stratosphere on a NASA high altitude balloon, and demonstrated its antenna-steering technology flawlessly. Shortly thereafter, Walker began working on a design to create a constellation of inflatable satellites and got two prototypes to “talk” to one another on the ground.

Next, Walker expects to deploy an inflatable 5G satellite in orbit attached to a cubesat. He is also working on two NASA proposals to send the large balloon reflector to the stratosphere and the Terahertz Space Telescope to orbit. Recently, Walker and his colleagues even pitched NASA on a space-based array made out of these inflatable telescopes, which would allow them to image the surface of exoplanets around Alpha Centauri, our closest stellar neighbor. Yet as with all things in space science, securing the funding for the mission will be almost as difficult as developing the technology. But with any luck, we may be hunting for habitable exoplanets using giant inflatable telescopes in the not-so-near future.

Local 'sci-fi' projects advance in NASA competition

http://tucson.com/news/blogs/scientific-bent/local-sci-fi-projects-advance-in-nasa-competition/article_74205956-3ef0-54d3-ab97-068131ad1091.html

Courtesy of Christopher Walker

High-tech gadgeteer Christopher Walker launched this balloon lifting the Stratospheric Terahertz Observatory from Antarctica in 2012.

8 hours ago  •  By Tom Beal

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Astronomer Christopher Walker has three slips of paper from fortune cookies taped to his door. One reads: “A great pleasure in life is doing what others say you can’t.”

Walker proposes to make a 10-meter (33-foot) telescope from a balloon tucked inside a larger carrier balloon and floated into near space from Antarctica. He hopes the fortune is prophetic.

So far, so good. In 2012, NASA gave him $200,000 to flesh out his proposal.

On Thursday, it awarded him up to $500,000 to develop and fly a prototype. He estimates a fully developed 10-Meter Sub-Orbital Large Balloon Reflector would cost about $8 million.

His is one of five projects remaining from the original 450 entries in the 2012 round of what are colloquially called the “sci-fi” awards, through which NASA encourages novel, risky ideas.

Walker said the ideas “can’t be too crazy, but they also can’t be too sane.”

Tom Prettyman, senior scientist with Tucson-based Planetary Science Institute, also advanced to the second round of the sci-fi awards, known officially as the NASA Innovative Advanced Concepts Program.

Prettyman proposes to build a muon detector for a future space mission that would allow scientists to perform an outer-space “CT scan” of asteroids, comets, or the subsurface of planets.

Muons are fundamental particles that are plentiful on Earth and can penetrate “through a kilometer of rock,” Prettyman said.

They were used by physicists and archaeologists in the ’70s to search the great pyramids of Egypt for hidden chambers and more recently to detect rising magma in volcanoes.

Prettyman thinks he can find enough muons in space and create a space-borne detector that would be valuable in a future space mission.

“It’s exciting,” said Prettyman, who said he met Walker at a symposium where some of the initial proposals were presented.

“There were just a gaggle of different ideas from all over the place — architects wanting to build space colonies and somebody proposing an induced coma for travel to Mars.”

Walker said the scientific payoff would be huge for his plan to place a large telescope and a terahertz detector above most of Earth’s atmosphere to look, at first, for water vapor in the cosmos.

Terahertz astronomy explores the millimeter and submillimeter wavelengths of light between infrared and microwaves.

He would be looking specifically at 557 gigahertz for the signature of water vapor — something that is impossible if peering through atmosphere, even in the dry air of Antarctica.

NASA developed the technology that allows him to fill 700 pounds of thin-film polyethylene with 17 million cubic feet of helium to act as a carrier balloon.

Walker has been floating high-tech gadgets from such balloons for the past 20 years.

What’s new is Walker’s concept of a balloon within a balloon.

His interior balloon, 20 meters in diameter, would have an aluminized, spherical portion 10 meters wide that would act as the telescope mirror.

It would sit inside the top of the carrier balloon, which would act as a protective radome, and also keep the mirror steady.

A 1-meter correcting mirror, needed in case the balloon does not inflate evenly, would focus light onto his detector.

It would be launched from the South Pole, climb to an altitude of 120,000 feet and float there, pushed by a dependable arctic vortex that would allow it to inscribe a circular pattern, returning to its starting position every 14 days.

After 100 days of gathering data, the telescope and supporting gantry would detach and float back to Earth on parachutes.

The carrier balloon expands crazily in the thin atmosphere to 100 meters in diameter, making its polyethylene skin 97 to 98 percent transparent — good enough for the kind of astronomy Walker conducts.

It’s also easy to correct the image at those wavelengths. “Our wavelengths are so long, our corrections are trivial,” Walker said.

In an optical telescope, an adaptive mirror needs to make 1,000 corrections a second.

At Walker’s wavelengths, “We’re talking millimeters in an hour. You could do this with ropes and pulleys.”

Steward Observatory director Buell Jannuzi calls Walker one of the founders of terahertz astronomy. He has built receivers for most of his 40-year career, including ones for the South Pole and the Heinrich Hertz Submillimeter Telescope on Mount Graham.

The balloon flights Walker usually does are of 14-day duration. “We call that a long-duration balloon,” he said. This project would rely on a super-pressurized helium balloon that NASA has developed — leading to an “ultra-long duration” balloon flight of 100 days or even more.

The goal in this second round is to build a half-sized prototype for a 12-hour flight from Fort Sumner, N.M.

Walker notes that the location is only 30 minutes from Roswell, N.M. — home to an array of alien visitation theories.

Where better to test out a sci-fi proposal?

Contact reporter Tom Beal at tbeal@tucson.com or 573-4158.

Stratospheric Terahertz Observatory (STO) surveys violent, star-making clouds of Milky Way Galaxy

Photo Credit: Christopher Walker Stratospheric Terahertz Observatory is prepared for launch from the Long Duration Balloon facility on the McMurdo Ice Shelf in January 2012. The telescope carried high-tech "radios" to tune into the violent dust clouds from where stars are born in galaxies.

http://www.spaceref.com/news/viewsr.html?pid=39805
Peter Rejcek, Antarctic Sun Editor: "All we are is dust in the wind." So sang the 1970s rock band Kansas for its peaceful, philosophical ballad about mortality. But the place from where the clouds of cosmic dust and gas blow that eventually forms stars and planets -- and, by extension, us -- is far less idyllic.

"These clouds of dust and gas aren't gently moving around. This is a very violent, nasty place in the interstellar medium. Terrible things are happening. Things are being ripped apart; gravity is shoving stuff together," said Christopher Walker , about six weeks before his team launched a giant balloon from Antarctica high into the Earth's atmosphere carrying a very special type of high-frequency radio.

The Stratospheric Terahertz Observatory (STO) won't be tuning into Kansas' greatest hits. Instead, it will pick up the faint, high-frequency radio signals emitted by carbon atoms within those violent interstellar clouds of gas and dust that are found in the Milky Way Galaxy.

"These clouds are actually made out of the debris of supernovas that went off long before the sun ever existed," Walker said. In turn, remnants from those explosions eventually coalesced -- or collapsed -- to form the sun. The planets were byproducts of the sun's formation.

It's an interstellar evolution -- birth, death and rebirth -- that still goes on today in this and other galaxies. The clouds in what astronomers call the interstellar medium, the matter that exists in the space between the star systems in a galaxy, play a key role in the process.

"In order to understand the lifecycle of all of this gas and dust in the Milky Way that goes from gas and dust to stars, back to gas and dust, back to stars, the formation of planets, we need to understand how these clouds of gas and dust form -- how long are they in this phase," Walker explained. "No one really knows. ... We can learn a lot just by listening to the faint radio signals coming from these atoms and molecules about what is going on out there."

A professor of astronomy at the University of Arizona , Walker is the principal investigator on the NASA -funded project, which is also supported by the National Science Foundation (NSF) through the U.S. Antarctic Program . The project includes a number of investigators and institutions, including the University of Arizona, Johns Hopkins University Applied Physics Laboratory (APL) , NASA's Jet Propulsion Lab , the University of Cologne in Germany, Arizona State University and Caltech .

STO is a balloon-borne observatory, using the same gondola and telescope that Johns Hopkins APL investigators had previously used for solar astronomy. It was launched Jan. 15 from the Long Duration Balloon (LDB) facility located on an ice shelf near McMurdo Station . It spent two weeks circling the Antarctic, thanks to a summertime vortex that moves over the continent during this time of year. STO flew in the stratosphere at around 125,000 feet or more -- about three times as high as commercial aircraft fly.

"We're halfway to space," noted Tony Stark, a co-principal investigator on the project and an astronomer at the Smithsonian Astrophysical Observatory . He also pioneered radio astronomy at the South Pole Station , particularly as the lead investigator on the Antarctic Submillimeter Telescope and Remote Observatory (AST/RO) Link to PDF file , a 1.7-meter diameter telescope that operated at the Pole for more than a decade.

A vehicle used in the balloon launches is parked outside of the two LDB hangar buildings.

"We were the first really successful winter experiment at the Pole," said Stark while sitting in the crowded mezzanine of the balloon hangar. "When we started, people said it couldn't be done. It was almost true. It was really difficult."

The science goals were similar -- investigations into the nature of the interstellar medium lifecycle. More than 100 papers were based on data from AST/RO, including the discovery that most galaxies experience sudden star-forming periods, or starburst, every 20 million years, based on observations of dust clouds in the center of the Milky Way Galaxy.

Eventually, AST/RO maxed out in terms of the frequencies it could detect through the high and dry atmosphere at the South Pole.

"It's water vapor that's our enemy. It absorbs the light we're trying to detect. The South Pole is good up to a certain frequency, and after that you need to get above everything," explained Walker, who made eight trips to Antarctica for the AST/RO experiment.

Enter STO, which sports the "most complicated high-frequency radios on Earth right now," according to Walker. The long-duration balloon carried the roughly two tons of gondola, telescope, radio receivers and associated gadgetry to the fringes of the Earth's atmosphere where interference from water vapor is far less of a problem.

The researchers believe the balloon platform will give them plenty of bang for the buck. A space-based mission would have cost at least $120 million when the team first proposed the project in 2007, according to Walker. The STO experiment will cost about one-twentieth of that.

The gondola carries two star cameras so the team knows which part of the Milky Way the telescope is pointing. It also boasts three gyroscopes to provide an inertial guidance system so the astronomers can point it to the places in the galaxy they want to map. Large solar panels provide the kilowatt of power needed to run the small, robotic observatory.

An onboard cryogenic system uses liquid helium to cool the ultra-high frequency radio receivers down to just a few degrees above absolute zero. There is also a receiver that can operate at atmospheric temperatures.

"This thing has all of the features and subsystems of an orbiting spacecraft," Walker said. "No one has yet put these kinds of detectors on the back of a balloon-borne telescope."

The team already has a proposal into NASA to build a new version of the gondola and telescope to probe even deeper into the Milky Way and other nearby galaxies, such as the Large Magellanic Cloud.

Dubbed GUSSTO, for Galactic/extragalactic Ultra/LDB Spectroscopic/Stratospheric Terahertz Observatory (GUSSTO), the one-meter telescope would fly on one of NASA's newly designed super-pressure balloons that can stay aloft for 100 days or more.

"STO is unique in what it can do, and it's also a precursor to GUSSTO, which we hope to start next year," Walker said. "It fills in a big gap in our knowledge of the lifecycle of galaxies like our Milky Way."