Look Up: Development of Concepts for NASA’s Next Flagship Telescope Begins; Two Ohio State Astronomers Lead Studies
While few of us think as far ahead as the 2030s, NASA clearly must. Its recent announcement of four contenders for its 2030s "flagship telescope" is a good indicator of how much time it takes to study, plan, develop — and then successfully build and launch — a telescope for the future.
In late February, NASA appointed two chairs to each of the four flagship telescope teams. Two of the eight chairs are Ohio State faculty members. Brad Peterson, professor and former chair of the Department of Astronomy, chairs the Large UV-Optical-IR Surveyor (LUVOIR) science and technology definition team, along with Debra Fischer from Yale University. Astronomy Professor Scott Gaudi chairs the Habitable Exoplanet Surveyor (HabEx) team, along with Sara Seager from the Massachusetts Institute of Technology.
These two studies, along with those of an X-Ray Surveyor mission and a Far-IR Surveyor mission, are now plotting their course to the 2019 finish line: submission of final reports to NASA, and ultimately the National Academy of Sciences’ 2020 Astronomy Decadal Survey, which sets priorities for federal investments in the 2020s. It is likely that one of these four mission concepts will be chosen as the top space-based mission priority to be developed during the 2020s and launched sometime in the 2030s.
Laura Lopez, assistant professor in astronomy, was named to the X-Ray Surveyor team.
“The overall landscape of the missions NASA selects concept studies for is largely guided by the ‘30-year vision for the NASA Astrophysics Roadmap’ done in 2012,” said David Weinberg, astronomy professor and chair. Both Weinberg and Gaudi played a major role in its writing.
“I think these two projects are widely regarded as having the best chance of being the top pick for NASA’s flagship astrophysics mission for the next decade, and I’m proud to say that no other institution in the country has two of the eight committee chairs on these four concept studies teams.”
The Clock is Ticking
NASA named team chairs in February; their teams are now in place and the clock is ticking. At the end of April — just days away — the teams will give NASA their initial thoughts on the task at hand. In August, each will submit a “study plan,” detailing timelines and resources needed to define goals, scope and cost of each telescope.
In March 2019, the teams must submit their reports — each making the best case for their observatory — to the National Academy of Sciences’ independent Decadal Survey committee. It will then rate and rank projects, advising NASA and the National Science Foundation on priorities.
Then, NASA will take the first steps toward realizing its next flagship for launch in the 2030s.
Team chairs selected their team from top applicants worldwide — a necessarily thorough and thoughtful process as each project’s chance for success rests on what every team member can contribute toward making the best possible case for their telescope.
As Peterson said, “It took us quite a while to select our team of 24 from the 136 applicants we reviewed. We needed a broad range of expertise to be absolutely sure that all the gaps were filled.”
“Fortunately, our team members are in place,” Gaudi said, “but first we had to evaluate a list of 80 applicants in order to choose the 16 we knew we needed."
Flagships-in-waiting: LUVOIR, the Uber-Hubble
LUVOIR’s team of 24 scientists and engineers, co-chaired by Peterson, will study this multi-purpose observatory capable of watching stars, galaxies and black holes form and evolve.
“When NASA announced late last year they were going to form these science study teams, I applied for the LUVOIR Team,” Peterson said. “LUVOIR is the most broadly capable of the four telescopes they selected and it is driven by the kind of deep studies that I most wanted to accomplish.”
Peterson describes LUVOIR’s mirror vividly, “Its 8-to-16-meter-wide mirror is more than three times the size of Hubble’s. It’s likely that it will have to be made of smaller segments that are then pieced together like a mosaic.
“Imagine the challenges involved in assembling — in one single piece — such an enormous mirror that has the exact required precision. I’m not sure that it would even be possible.
“Assembling a mirror in segments has heritage in both ground-based telescopes, such as the Keck telescopes in Hawaii and NASA’s upcoming flagship mission, the James Webb Space Telescope (JWST). The JWST mirror is made of beryllium, which is poisonous but can work at very low temperatures. It’s coated with gold for high reflectivity in the infrared. The LUVOIR segments, on the other hand, will be easier to make because the telescope will operate at room temperature and will be coated with other metals, mostly silver, for high reflectivity in the ultraviolet.
“The challenges of assembling LUVOIR’s mirror are more than worth it. We all believe that its most exciting feature is not just its potential to find Earth-size worlds circling nearby stars — which, face it, is pretty exciting in itself — but its capability to analyze their atmospheres for biological signs will determine if those worlds ARE actually Earth-like.
“What an amazing possibility this is.”
HabEx: the Planet Hunter
The HabEx team, co-chaired by Gaudi, consists of 16 astronomers and engineers. While HabEx shares many similarities with LUVOIR — including searching for and studying Earth-size planets around other stars — HabEx is designed for the specific goal of planet-watching.
“Early last year, when NASA first solicited input from the community about which missions to study, we solicited white papers, collated them and other input, and cogitated about priorities,” Gaudi said. “We looked at the existing technology, the likely amount of money available for such a mission, and identified large-scale priorities.
“In order to even begin to determine the optimal mission design, first you have to come up with its architecture — the overall structure and framework of the mission and study everything — the mirror, the size, the instrument suite, where the spacecraft will be located.
“Really, the first question is: What do we NOT know how to do?
“In the end, you have to make sure it’s affordable, maximize the science, minimize the cost of the technology and the overall risk — and deal with the idea that it might not work.”
To be a successful planet hunter at nearly unimaginable distances from our home planet requires “eyes” capable of penetrating deep into the universe.
“It is difficult to explain how hard it is to see a planet like the Earth orbiting close to another star that is over a billion times brighter,” Gaudi said. “A good analogy might be that it’s like trying to detect a firefly sitting next to a spotlight a few feet away from it, but it’s sitting in LA — and you’re standing in New York City.
“In order to see anything, you need something to block out starlight. You can either install a coronagraph in the telescope itself or build a star shade — something the size of a baseball diamond out of a big piece of metal with incredibly sharp edges. This will block the light from the star so you can see the planet; then all you have to do is make sure it stays aligned!
“HabEx is optimized to search for and image Earth-size worlds in their stars’ habitable zones, where liquid water can exist,” Gaudi said.
“Its 4-8 meter mirror will be created to zone in on and determine how common terrestrial worlds beyond the solar system may be and then assess a whole range of their characteristics.
“The primary mission of HabEx is find, study and characterize Earth-like planets. We hope we can do other science as well, but that is not the priority goal.
“Is it stressful? Time-consuming? Exhausting? Yes. Is it worth it? Are you kidding? Trying to accomplish the long-standing goal of finding life on other planets is not only compelling to everyone alive on this planet, but for me personally. What if I were part of the team that actually found life? How cool would that be!”
Also Very Much in the Running
The Far-Infrared Surveyor can see very long wavelengths of invisible light in a range of the electromagnetic spectrum that reveals parts of the universe otherwise undetectable: objects enshrouded in dust, such as stars and planets in the process of forming, interstellar compounds that may have led to life and the very first galaxies ever formed.
The X-Ray Surveyor also targets invisible parts of the universe. At such high energies, it could show how black holes began, how galaxies formed around them and how the whole structure of the universe shaped up. Lopez, assistant professor of astronomy, was selected as a member of its team.
“X-Ray Surveyor will be a successor to the Chandra X-ray Observatory, launched in 1999, which is currently in orbit,” Lopez said.
“X-rays are produced by astronomical objects with hot temperatures of millions of degrees,” she explained. “Many kinds of astrophysical systems emit X-rays: clusters of galaxies, active galactic nuclei — supermassive black holes at centers of galaxies — supernova remnants and binary star systems with neutron stars or black holes. X-rays are absorbed by the Earth's atmosphere, so X-ray telescopes must be in space in order to detect X-ray emission from these objects.
“I study supernova remnants, the objects leftover up to a hundred thousand years following supernova explosions. I use X-ray telescopes to map the hot gas in supernova remnants and measure the geometry and the elements synthesized in the explosions to probe exactly how the star exploded at the end of its life. This is an image I took with the Chandra X-ray Observatory.”
Image: A simulated image of a solar system twin as seen with the proposed High Definition Space Telescope (HDST) — a specific version of a LUVOIR-like telescope broadly similar to what LUVOIR will likely be. Image of Venus, Earth and Jupiter relevant to both HabEx and LUVOIR. Image credit: L. Pueyo, M. N’Diaye (STScI)