Let your mind wander for a moment and let it land on the most exciting and meaningful NASA mission that you can imagine. An undertaking, perhaps, that would send astronauts into deep space, that would require enormous technological innovation, and that would have ever-lasting science returns.

Many will no doubt think of Mars and the dream of sending astronauts there to explore. Others might imagine setting up a colony on that planet, or perhaps in the nearer term establishing a human colony on the moon. And now that we know there’s a rocky exoplanet orbiting Proxima Centauri — the star closest to our sun — it’s tempting to wish for a major robotic or, someday, human mission headed there to search for life.

All are dream-worthy space projects for sure. But some visionary scientists (and most especially one well-known former astronaut) have been working for some time on another potential grand endeavor — one that you probably have not heard or thought about, yet might be the most compelling and achievable of them all.

It would return astronauts to deep space and it would have them doing the kind of very difficult but essential work needed for space exploration in the far future. It would use the very costly and very powerful Space Launch System (SLS) rocket and Orion capsule being built now by NASA and Lockheed Martin respectively. Most important, it would almost certainly revolutionize our understanding of the cosmos near and far.

At a recent meeting of the House Science Committee, chairman Lamar Smith, said of the hearing’s purpose that, “Presidential transitions offer the opportunities to reinvigorate national goals. They bring fresh perspectives and new ideas that energize our efforts.”

That said, here’s the seemingly feasible project that fires my imagination the most.

It has been quietly but with persistence promoted most visibly by John Grunsfeld, the former astronaut who flew to the Hubble Space Telescope three times to fix and upgrade it, who has spent 58 hours on spacewalks outside the Shuttle, and towards the end of his 40 years with the agency ultimately became an associate administrator and head of the agency’s Science Mission Directorate.

His plan: Build a segmented space telescope mirror that is 16 meters (52 feet) in diameter or larger, package it into one or several payload fairings and launch it into deep space. Accompanying astronauts would put it together either at its final destination or at a closer point where it could then be propelled to that destination.

This would provide invaluable humans-in-space experience, would put the Orion and SLS to very good use in advance of a projected human mission to Mars, and would deploy the most penetrating telescope observing ever. By far.

No mirror with a diameter greater than 3.5 meters (11.5 feet) has ever been deployed in space, although the the James Webb Space Telescope mirror will be substantially larger at 6.5 meters (21 feet) when launched in 2018. The largest ground telescopes are in the 10-meter (33 foot) range.

What Grunsfeld’s space behemoth would provide is an unprecedented power and resolution to see back to the earliest point possible in the history of the universe, and doing that in the ultraviolet and visible wavelengths. But perhaps more significantly and revolutionary, it would supercharge the agency’s ability to search for life beyond Earth.

Like nothing else currently in use or development, it would provide a real chance to answer what is arguably humanity’s most fundamental question: Are we alone in the universe?

Grunsfeld has been introducing people to the project/vision inside NASA for some time. He also told me that he has spoken with many members of Congress about it, and that most have been quite supportive. Now he’s starting to make the case to the public.

“We need our leaders to be bold if we want to stay in the forefront of science and engineering,” he said. “Assembling a 16-meter telescope in space would not be easy by any means. But we can do it and — this is the key — it would be transformational. It’s a rational thing to do.”

His confidence in the possibility of launching the segmented mirror parts and having astronauts assemble them in space comes, he says, from experience. Not only has he flown on the space shuttle five times and has his three very close encounters with the Hubble, but he has also overseen the difficult process of getting the JWST project — with its pioneering segmented, folding mirror — back on track after large budget overruns and delays. He’s also trained in astrophysics and is enamored of exoplanets.

“If your goal is to search for inhabited planets, you just have to go up to the 16-meter range for the primary telescope mirror,” he said.

“Think about it: if we sent up something smaller, it will give us important and potentially very intruiging information about what planets might be habitable, that could potentially support life. But then we’d have to send up a bigger mirror later to actually make any detection. Why not just go to the 16-meter now?”

While all this may sound to many like science fiction, NASA actually has a team in place studying the science and technology involved with a very large space telescope, and has funded studies of in-space assembly as well.

The current team is one of four studying different projects for a grand observatory for the 2030s. Their mission is called LUVOIR (the Large UV/Optical/IR Surveyor), and both it and a second mission under study (Hab-Ex) have exoplanets as a primary focus. It was Grunsfeld and Paul Hertz, director of NASA’s astrophysics division, who selected the four concepts for more in-depth study based in large part on astronomy and astrophysics community thinking and aspirations, especially as laid out in the 2013 Thirty-Year Astrophysics Visionary Roadmap.

The LUVOIR team started out with the intention of studying the engineering and technological requirements — and science returns — of a space telescope between 8 and 16 meters in diameter, while Hab-Ex would look at the 4 to 7 meter option for a telescope designed to find exoplanets. Grunsfeld addressed the LUVOIR study team and encouraged them to be ambitious in their thinking — a message delivered by quite a few others as well. What’s more, a number of study team members were inclined towards the 16-meter version from the onset.

The LUVOIR team has not addressed the issue of assembly in space — their goals are to understand the science made possible with telescopes of different sizes, to design an observatory that can be repaired and upgraded, and to determine if the technology to pull it all together is within reach for the next decade or two.

A key issue is how large a folded up mirror the launch vehicle rocket nose cone (the fairing) can hold. While the current version of the SLS would certainly not accommodate a 16-meter segmented mirror, team study scientist Aki Roberge — an astrophysicist at the Goddard Space Flight Center — said that the team just recently got the good news that a next generation SLS fairing looks like it could well hold a folded mirror of up to 15 meters. Quite a few “ifs” involved, but still promising.

“We’re still in the midst of our work, but it’s clear that a LUVOIR with a large aperture (mirror) gives us a major science return,” she said. “Going up to nine meters would be a major leap forward, and going to 16 would be a dramatic advance on that.”

“But we have to assess what we gain in terms of going large and what we might lose in terms of added technical difficulty, cost and time.” As is, the 9 or 16-meter project — if selected — would not be ready to launch until the mid 2030s. All the great space observatories and missions have had decades-long gestation periods.

The results from the LUVOIR and other formal NASA study teams will be reviewed by the agency and then assessed by a sizeable group of experts convened by the National Academy of Sciences for the 2020 Astrophysics Decadal Survey. They set the next decade’s topic and mission priorities for the astronomy and astrophysics communities (as well as others) — assessments that are sent back to NASA and generally followed.

One of Grunsfeld’s goals, he told me, is to make the assembled-in-space 16-meter telescope a top Decadal Survey priority. While supportive of the LUVOIR efforts, he believes that including astronauts in the equation, deploying a somewhat larger mirror even if the difference in size is not great, and making a mirror that he says will be easier to fix and upgrade than a folded up version, gives the assembled-in-space option the advantage.

These images, which are theoretical simulations using the iconic Hubble Deep Field image, are adjusted to reflect the light collected by telescopes of different sizes. They show the increased resolution and quality of images taken by a 16-meter telescope, a 9-meter, and the Hubble Space Telescope, which is 2.4 meters in diameter. They illustrate pretty clearly why astronomers and exoplanet hunters want ever larger telescope mirrors to collect those photons from galaxies, stars and planets.

Whether or not the LUVOIR project is selected to be a future NASA flagship observatory, and whether or not it will be an assembled-in-space version of it, many at the agency clearly see human activity and habitation in space (as well as on planets or moons) as a necessary and inevitable next step.

Harley Thronson is the senior scientist for Advanced Concepts in Astrophysics at Goddard, and he has worked on several projects related to how and where astronauts might live and work in space.

He said this research goes back decades, having gained the attention of then-NASA Administrator Dan Goldin around 2000. It has recently experienced another spurt of interest as the agency has been assessing opportunities for human operations beyond the immediate vicinity of the Earth.

“It’s inevitable that the astronomy community will want and need larger space observatories, and so we have to work out how to design and build them, how and where they might be assembled in space, and how they can be serviced,” Thronson said. The JWST will not be reachable for upgrades and servicing, and Congress responded to that drawback by telling NASA will make sure future major observatories can be serviced if at all possible.

Thronson said that he supports and is inspired by the idea of a 16-meter space telescope, and he agrees with Grunsfeld that assembly in space is the wave of the future. But he said “I’m not quite as optimistic as John that we’re ready to attack that now, though it would be terrific if we were.”

Part of Thronson’s work involves understanding operation sites where space telescopes would be most stable, and that generally involves the libration points, where countervailing gravity pulls are almost neutralized. LUVOIR, like JWST, is proposed for the so-called Sun-Earth L-2 point, about one million miles outward from Earth where the Earth and sun create a gravitational equilibrium of sorts.

Thronson said there has been some discussion about the possibility of assembling a telescope at a closer Earth-moon libration point and then propelling it towards its destination. That assembly point could, over time, become a kind of depot for servicing space telescopes and as well as other tasks.

As a sign of the level of interest in these kind of space-based activities, NASA last year awarded $65 million to six companies involved in creating space habitats for astronauts on long-duration missions in deep space.

At the time, the director of NASA’s Advanced Exploration Systems, Jason Crusan, said that “the next human exploration capabilities needed beyond the Space Launch System rocket and Orion capsule are deep space, long duration habitation and in-space propulsion. We are now adding focus and specifics on the deep space habitats where humans will live and work independently for months or years at a time, without cargo supply deliveries from Earth.”

Not surprisingly, building and maintaining telescopes and habitats in space will be costly (though less so than any serious effort to send humans to Mars). As a result, how much support NASA gets from the White House, Congress and the public — as well as the astronomy and astrophysics communities — will determine whether and when this kind of space architecture becomes a reality.

John Grunsfeld, who has walked the walk like nobody else, plans to be stepping up his own effort to explain how and why this is a vision worth embracing.

( Creator and Writer ) Marc Kaufman is the author of two books about space: “Mars Up Close: Inside the Curiosity Mission” and “First Contact: Scientific Breakthroughs in the Search for Life Beyond Earth.” He is also an experienced journalist, having spent three decades at The Washington Post and The Philadelphia Inquirer. He began writing the column in October 2015, when NASA’s NExSS initiative was in its infancy. While the “Many Worlds” column is supported and informed by NASA’s Astrobiology Program, any opinions expressed are the author’s alone. Read More

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