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The future of space astronomy may depend on two large ground telescopes



This article was originally published in the January 21, 2019 issue of the SpaceNews magazine.

At the largest conference of astronomers in the United States, the largest astronomy mission under development was virtually a non-appearance.

The partial government shutdown, which began on December 22, prevented NASA officials from attending the January 2010 American Astronomical Society (AAS) winter convention in Seattle. These included the officials who handled the James Webb Space Telescope, a mission that many astronomers treated with both anticipation and concern: the former for its scientific potential, the latter for its recent cost overruns and delays.

The absence of the space agency meant the cancellation of a city hall dealing with NASA astrophysics programs and another meeting with JWST. Northrop Grumman, the main contractor of the telescope, also stayed behind at the conference. In a break with recent years, it declined the demand for interviews with company officials to discuss the status of the telescope.

But the lack of evidence for JWST at the AAS meeting was no proof of the lack of progress on the mission amidst the shutdown "Work on JWST at Northrop Grumman and at Space Telescope will continue despite the government's shutdown", said Ken Sembach, director of the Space Telescope Science Institute (STScI), during a meeting of the Town Hall on January 7 at the conference on his institute. He reported that JWST's spacecraft element had just successfully completed a series of vibration tests.

  A reproduction of the Giant Magellan Telescope, which is expected to enter service in the 2020s on the Chilean Las Campanas Peak. The proposed US ELT program aims to provide US $ 1 billion in federal funding for GMT and TMT. Credit: Mason Media Inc. via GTMO
A replica of the Giant Magellan Telescope, expected to be operational in the 2020s at Las Campanas Peak in Chile. The proposed US ELT program aims to provide US $ 1 billion in federal funding for GMT and TMT. Credit: Mason Media Inc. via GTMO

Astronomers feared that JWST could not enter space due to the delays before the Hubble Space Telescope reached its end. Launched in 1990, Hubble was last serviced in 2009 and has recently had some issues, such as: However, a problem with the Wide Field Camera 3 instrument in early January

Hubble executives are optimistic that Hubble will be following the launch of JWST will work well. Tom Brown, Hubble Mission Manager at STScI, said at an AAS conference session, technical analysis of Hubble's instruments and key subsystems suggests they should continue at least 2025. "We expect Hubble to continue to be a unique observation center in the 2020s," he said.

Note the future gap

Astronomers' greater concern concerns the long-term future of space astronomy. Mission to JWST is the Wide-Field Infrared Survey Telescope (WFIRST), which is set to launch in the mid-2020s, just a few years after JWST, but WFIRST is more a complement to JWST with capabilities other than a successor.

A true successor JWST will emerge from the next Decadal Astrophysics Survey, with a final report to be published in late 2020. Four Concepts for Large Space Observatories are being investigated for the Decadal study, three of which comprise large optical or infrared telescopes (the fourth is an X-ray telescope, Lynx) a successor to the Chandra X-ray Observatory.)

The Decadal Survey recommends one proposed space telescopes, and NASA agrees. It is not expected to be in space before the mid-2030s, given NASA's budgets and schedules. However, JWST has only a five-year main task. While astronomers expect it to be in operation for at least ten years, there is no way to fix it if something goes wrong or even refuels its stationary engines.

There is also skepticism that the selected mission will actually be completed by the mid-2030s. Those working on the concept studies have argued that they work more thoroughly than their predecessors, and address potential issues early on. However, some astronomers expect unavoidable problems to delay takeoff.

"If we look at the James Webb model, I can say for sure that none of these problems are likely to hit the market and continue to do science until the 2040s," said Ian Crossfield, assistant professor of physics at Massachusetts Institute of Technology, which studies exoplanets. "There will be a big gap when JWST starts on its current schedule."

Great Rescue Telescopes

A solution to this future space telescope gap could come from the ground. A new generation of so-called extremely large telescopes (ELTs) is currently being developed and is expected to go into operation in the 2020s. With mirrors between 25 and 40 meters in diameter, they are far larger than anything space has provided for decades. Despite the limitations of the soil, such as weather and atmospheric distortions, they have years of unrivaled capabilities.

"Nothing planned for outer space will be able to touch this science until the 2040s." said Quinn Konopacky, an assistant professor of physics at the University of California at San Diego, who studies the formation of stars and planets. "If you want to be a leader in exoplanet research over the next two decades, you need TMT and GMT."

It referred to two of these great ELTs being developed: the Giant Magellan Telescope in Chile and the Thirty Meter Telescope in Hawaii. GMT will combine seven large mirrors to a primary mirror of 24.5 meters in diameter. TMT will make a primary mirror from nearly 500 small mirror segments, as the name implies, having a diameter of 30 meters.

The observatory for GMT at Las Campanas Peak in Chile is taking shape, and its seven mirrors are in various stages of production in a laboratory in Arizona. The work on TMT was hampered by legal disputes over the construction of the telescope on Hawaii's Mauna Kea. The project officials, however, are hopeful. After the Supreme Court of Hawaii eventually fell in its favor, they can begin construction this spring

However, a problem for many astronomers is that GMT and TMT are not developed by government agencies but by consortia of universities and industry non-profit organizations. Astronomers who are not part of the consortium can not use them.

  The 8.4-meter mirrors of the GMT are manufactured in the Richard F. Caris Mirror Lab under the football stadium of the University of Arizona. A worker is shown cleaning the surface of one of the seven GMT mirrors. Credit: GMTO.ORG
The 8.4-meter mirrors of GMT are manufactured at the Richard F. Caris Mirror Lab under the football stadium of the University of Arizona. A worker is shown cleaning the surface of one of the seven mirrors of GMT. Credit: GMTO.ORG

For this reason, a concerted effort was made at the AAS meeting for the so-called US ELT program, a proposal to grant federal funding to these two observatories in return for free access to an American one Astronomers like NASA-operated space telescopes. A specific proposal for the program called for US $ 1 billion of National Science Foundation funding for GMT and TMT in return for 25% of the observation time each.

"That sounds like a large number, but that's in line with the investments the NSF has made in the last decade, the last 15 years, in major scientific institutions," said David Silva, director of the National Optical Astronomy Observatory operates several telescopes. He added that a National Academies study on exoplanet science last year recommended that NSF invest in the two observatories.

The two observatories say that they would be prepared to give part of their observation time to the broader astronomical community in exchange for the Astronomical Community financial support and stability that the NSF would provide. "Your financial support will be very helpful in meeting the timetable and adhering to our overall plan," said Pat McCarthy, vice president of GMT. "It's a real benefit to know that the entire US community is behind us."

The NSF will provide the $ 1 billion, a process that can take several years and is likely to require lobbying to top up NSF's overall budget. However, astronomers like MIT's Crossfield argued that NASA could help too.

NASA is generally associated with missions from space, he said, but the agency also supports groundscopes, including the Keck Observatory and the infrared telescope facility on Mauna Kea. "There are many precedents for NASA's involvement in ground-based astronomy when it believes it serves NASA's programmatic scientific interests," he said. "I think the US ELT program is absolutely for these interests."

He suggested that NASA could fund instruments for one or both of these observatories, just like a few years ago for an instrument at an observatory in Arizona. "That would be a very interesting way forward that would serve the US exoplanet community," he said.

ELT advocates have no problem with NASA jumping aboard. "We would welcome NASA's investment in our huge machines," Silva said when asked at an AAS meeting about the space agency that contributed to the US ELT program.

But no one from NASA was able to comment on the idea. Thanks to the shutdown, no one from NASA could attend.


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