The eXtreme Deep Field

The Hubble telescope, which captured this iconic image of a region in the constellation Ursa Major, was a top priority of a past decadal survey.Credit: NASA/ESA/University of California Santa Cruz/Leiden University/The HUDF09 Team

Dream big, but be realistic. That’s the message for US astronomers as they begin debating what their field should do for the next ten years.

The US National Academies of Sciences, Engineering, and Medicine have just launched astronomy’s ‘decadal survey’, the highly influential process of prioritizing which telescopes and space missions Congress and government science agencies should support.

Past decadal surveys have cleared the way for groundbreaking missions such as NASA’s Chandra X-Ray Observatory. But they have also ensnared the space agency in financial problems and delays. Neither of the large space missions recommended by the 2001 and 2010 decadal surveys — the James Webb Space Telescope and the Wide Field Infrared Survey Telescope (WFIRST), respectively — has yet launched.

The 2020 decadal survey will develop detailed cost estimates for each project, as well as guidance for what managers can do if money gets tight. “We have to look at the budget reality while also doing things that are visionary,” says Fiona Harrison, an astronomer at the California Institute of Technology in Pasadena and co-chair of the effort.

Responding to problems of racism and harassment in science, the survey will also assess the state of astronomy as a profession and make recommendations for how it can improve. “We’re going to go there,” says the other co-chair, Robert Kennicutt, an astronomer at the University of Arizona in Tucson and Texas A&M University in College Station.

He and Harrison described their plans for the decadal survey on 9 January at a meeting of the American Astronomical Society in Seattle, Washington.

Anyone interested in being on one of the project’s many panels can apply until 22 January. White papers describing visionary science are due on 19 February. But both deadlines could be extended given the ongoing partial US government shutdown.

Making the list

Past decadal surveys have been hugely popular with key members of Congress, who see them as a unified wish list from astronomers, ranking projects of all sizes. “This community is very good about getting in a small room, getting out the knives and stabbing each other in the back,” says Jeremy Weirich, vice-president for corporate strategy at the Association of Universities for Research in Astronomy in Washington DC, who formerly worked on the Senate’s spending committee. “But when the doors open and you come out, you are good at speaking with a common voice.”

Programme managers at NASA, the National Science Foundation (NSF) and the Department of Energy rely on the decadal survey when deciding what to fund. But projects can unexpectedly consume years of budgets and planning. The 2001 survey estimated that the Webb telescope would cost US$1 billion. Now, it is slated to launch in 2021 at a cost of $8.8 billion. Meanwhile, the top space mission from the 2010 survey — WFIRST — is looking at a launch in the mid-2020s at the earliest.

Hoping to stave off problems this time around, NASA has already asked astronomers to draw up detailed plans on four possible big space missions. They include a Hubble-on-steroids space telescope that would span wavelengths from ultraviolet to infrared with a massive 15-metre mirror; an innovative X-ray observatory; a technologically advanced infrared telescope; and a 4-metre telescope with a starshade to study exoplanets.

Their prices are not yet set, although NASA has required each of the four to produce design options that would cost between $3 billion and $5 billion. Each is much more developed, at least on paper, than Webb and WFIRST were at this point in previous survey cycles.

Thinking big

The latest decadal survey will also tackle the future of big observatories on Earth. That means assessing the forced marriage of two formerly competitive projects that had been working with private funding but now need NSF cash to finish the job. The Giant Magellan Telescope, with a 24.5-metre primary mirror, is already under construction in Chile and is aiming for first light in 2025. The Thirty Meter Telescope is likely to resume attempts to build on Mauna Kea, Hawaii, this year, after protests from some Native Hawaiian groups derailed it in 2015. “Both of them are ready to go,” says Anthony Beasley, director of the National Radio Astronomy Observatory in Charlottesville, Virginia.

Representatives from both telescopes roamed the Seattle meeting, wearing badges with heart logos that declared they loved the pair, collectively rebranded as the US Extremely Large Telescope programme. Underlying the merger is the clear message that European astronomers are in the lead, as they work on what will be the world’s largest telescope, a 39-metre observatory in Chile that is aiming for first light by 2025.

Many astronomers say that getting the NSF to help support the US effort, with an investment of roughly $1 billion, is the only way to get both US projects across the finish line and allow the country’s astronomers to compete with those in Europe. “This is the only chance we have left if we want to be involved,” said Debra Elmegreen, an astronomer at Vassar College in Poughkeepsie, New York, at the meeting. With public money, at least 25% of the time on each telescope would be open to applications from any US astronomer.

The decadal survey will also consider how all recommended US projects, from large to small, fit with international collaborations such as Europe’s own road map for astronomy. The US survey is slated to come out in the second half of 2020.

“The game is afoot,” says Beasley.