- Jan 27, 2020
- 751
- 145
- 5,080
“Decadal survey” considers $1.8-billion bailout for Thirty Meter Telescope and Giant Magellan Telescope
1 SEP 2021, 1:20 PM, BY DANIEL CLERY
The Giant Magellan Telescope (left) and the Thirty Meter Telescope, shown in artists’ concepts, are making a joint pitch for federal funding.GIANT MAGELLAN TELESCOPE/GMTO CORPORATION; TMT INTERNATIONAL OBSERVATORY
Roughly every 10 years since the 1960s, U.S. astronomers have provided a valuable show of consensus to U.S. funding agencies and Congress by agreeing on which questions and new facilities are critical to the field. But the current “decadal survey,” known as Astro2020 and scheduled to be published at any time, faces a particularly knotty question, one that could settle whether the United States stays in the front rank of ground-based observing. Should the National Science Foundation (NSF) come to the rescue of two struggling private projects to build giant optical telescopes in exchange for a chunk of observing time?
The future of the Giant Magellan Telescope (GMT)* and the Thirty Meter Telescope (TMT)** likely depends on whether the survey recommends that NSF spend what sources put at $1.8 billion to support a recently forged partnership between the projects. If it does, other proposals could lose out, such as a continent-spanning radio array and detectors for neutrinos and other cosmic particles. (Space missions are ranked separately.)
Understandably, astronomers are divided. The GMT-TMT proposal “is critical for the field to thrive,” says John O’Meara, chief scientist of the W. M. Keck Observatory. With Europe pushing ahead with its own giant telescope, “If a federal partnership does not happen, I believe that the U.S., which has been the international leader in the field of astronomy for a century, will pass that role on to Europe,” says Wendy Freedman of the University of Chicago. But Richard Ellis of University College London, former director of the Palomar Observatory, believes rescuing both telescopes would cost “too much money and would eclipse so many other things.”
For ground-based optical astronomers, giant telescopes with mirrors about 30 meters across are the obvious next step after the huge advances made with today’s 10-meter scopes. O’Meara says there is no other way to image an Earth-like planet around a red dwarf star, for example. “No matter how tricky you get, the laws of physics overrule you,” he says. “Aperture is king.”
Telescope designers have been planning such behemoths since the 1990s, and the European Southern Observatory is laying the foundations for its 39-meter Extremely Large Telescope (ELT) on the summit of Cerro Armazones in Chile, with first light due in 2027. But divisions over technology and funding have hampered the two U.S.-led projects. The TMT, to be built in Hawaii by the California Institute of Technology and the University of California (UC), will have a honeycomb mirror built of 492 hexagonal segments. In contrast, the GMT, led by the Carnegie Institution for Science, will arrange six 8.4-meter mirrors around a seventh, giving the Chile-based telescope an aperture of 24.5 meters. The projects had early talks about joining forces, but “there was no desire to abandon their telescopes,” Ellis says. “Once money started flowing, it was impossible to merge.”
The 2000 decadal survey rated a giant segmented-mirror telescope (essentially the TMT) as the No. 1 U.S. priority in ground-based projects. NSF started discussions with the TMT about partnership in the project, but backed away after the GMT objected. In the 2010 decadal a giant ground-based scope dropped to No. 3, behind a large survey telescope and an instrument innovation program—a decision that essentially killed federal involvement for another 10 years. “That really damaged the momentum of the project,” says Garth Illingworth of UC Santa Cruz.
Both projects set out to raise their own funds, but neither has sufficient money so far. The TMT has also faced continued opposition, including legal challenges, from Native Hawaiians to building such a large structure on Mauna Kea, which they consider sacred.
For the current decadal, the projects have finally united into a two-telescope package that would give all U.S. astronomers access to at least 25% of the observing time in exchange for the $1.8 billion (a figure that is not officially confirmed). This deal, dubbed US-ELT, would give U.S. astronomers an advantage over Europeans: front rank telescopes in both the Northern and Southern hemispheres. “The U.S. really does need [giant telescopes] to follow up on other investments on the ground and in space,” Illingworth says.
Those include the James Webb Space Telescope (JWST), set for launch later this year. The JWST should revolutionize astronomy by picking out objects including the earliest galaxies with its pin-sharp infrared eyes, but fine-grained spectrometers on the ground will be needed to follow up on some discoveries. Then there is NSF’s Vera C. Rubin Observatory in Chile, a survey telescope that from 2023 will carry out a census of the sky nearly every night, identifying thousands of objects demanding closer investigation. “It would be an admission of defeat to let Europe take over this area,” Illingworth says.
Others say the U.S. giants are too far behind to avoid that outcome, and the costs are prohibitive. “How can you make a sales pitch for two telescopes when the rest of the world has one?” Ellis asks. Astronomers also worry about the consequences of funding US-ELT for projects such as a next-generation upgrade of the Very Large Array Radio Telescope (ngVLA) in New Mexico into a continent-spanning network of 263 dishes. “The ngVLA is no silly idea, it’s something we must do,” O’Meara says. The science cases behind upgrading the IceCube Neutrino Observatory at the South Pole and building a next-generation detector for the cosmic microwave background radiation are similarly compelling.
The decadal may also decide that U.S. astronomy doesn’t need to pursue an endless quest for ever-greater expanses of glass on the ground. Some astronomers think the greatest potential for discovery lies in modest new telescopes, or upgrades of older ones, with multiobject spectrographs that can scrutinize thousands of objects at once. “It’s a different vision,” says Ray Carlberg of the University of Toronto, and one that requires a team-based approach more familiar to particle physicists. “So much more science can be done with large groups of collaborators working together on a range of projects,” says Jennifer Marshall of Texas A&M University, College Station, project scientist of the proposed Maunakea Spectroscopic Explorer.
The 20-strong decadal committee, after a delay of more than 6 months because of the COVID-19 pandemic, should soon deliver its verdict, bringing joy to some and misery to others. “You need really big pockets” to build giant telescopes, Carlberg says. “The only people who can build them now are nations or consortia of nations.”
See: https://www.science.org/content/art...pes-balance-u-s-astronomers-debate-priorities
* Light gathered by the Giant Magellan Telescope (GMT) from the edge of the universe will first reflect off of the seven primary mirrors, then reflect again off of the seven smaller secondary mirrors, and finally, down through the center primary mirror to the advanced CCD (charge coupled device) imaging cameras. There, the concentrated light will be measured to determine how far away objects are and what they are made of.
The GMT primary mirrors are made at the Richard F. Caris Mirror Lab at the University of Arizona in Tucson. They are a marvel of modern engineering and glassmaking; each segment is curved to a very precise shape and polished to within a wavelength of light—approximately one-millionth of an inch. Although the GMT mirrors will represent a much larger array than any telescope, the total weight of the glass is far less than one might expect. This is accomplished by using a honeycomb mold, whereby the finished glass is mostly hollow. The glass mold is placed inside a giant rotating oven where it is “spin cast,” giving the glass a natural parabolic shape. This greatly reduces the amount of grinding required to shape the glass and also reduces weight. Finally, since the giant mirrors are essentially hollow, they can be cooled with fans to help equalize them to the night air temperature, thus minimizing distortion from heat.
One of the most sophisticated engineering aspects of the telescope is what is known as “adaptive optics.” The telescope’s secondary mirrors are actually flexible. Under each secondary mirror surface, there are hundreds of actuators that will constantly adjust the mirrors to counteract atmospheric turbulence. These actuators, controlled by advanced computers, will transform twinkling stars into clear steady points of light. It is in this way that the GMT will offer images that are ten times sharper than the Hubble Space Telescope’s.
The location of the GMT also offers a key advantage in terms of seeing through the atmosphere. Located in one of the highest and driest regions on earth, Chile’s Atacama Desert, the GMT will have spectacular conditions for more than 300 nights a year. Las Campanas Peak (“Cerro Las Campanas”), where the GMT will be located, has an altitude of over 2,550 meters or approximately 8,500 feet. The site is almost completely barren of vegetation due to lack of rainfall. The combination of seeing, number of clear nights, altitude, weather and vegetation make Las Campanas Peak an ideal location for the GMT.
See: https://www.gmto.org/overview/
** The Thirty Meter Telescope is a new class of extremely large telescopes that will allow us to see deeper into space and observe cosmic objects with unprecedented sensitivity. With its 30 m prime mirror diameter, TMT will be three times as wide, with nine times more area, than the largest currently existing visible-light telescope in the world. This will provide unparalleled resolution with TMT images more than 12 times sharper than those from the Hubble Space Telescope. When operational, TMT will provide new observational opportunities in essentially every field of astronomy and astrophysics. Observing in wavelengths ranging from the ultraviolet to the mid-infrared, this unique instrument will allow astronomers to address fundamental questions in astronomy ranging from understanding star and planet formation to unraveling the history of galaxies and the development of large-scale structure in the universe.
The Thirty Meter Telescope will be the amongst the largest ground-based observatories in the world and will provide new observational opportunities in essentially every field of astronomy and astrophysics. Astronomers will pursue further advancement of our inderstanding in several key science areas, including:
See: https://www.ucobservatories.org/observatory/thirty-meter-telescope/
See: https://www.tmt.org/page/science-themes
In the quest for an Extra-Large Telescope (ELT), the U.S. has managed to produce two competing projects, the Thirty Meter Telescope (TMT) and the Giant Magellan Telescope (GMT). Both have received shortfalls in funding, and neither appears likely to begin operations before the decade is out; each might put the financial skids on the other. The TMT's early stages of construction on the Hawaiian volcano Mauna Kea — a site unrivaled for pristine views of the Northern Hemisphere sky — sparked protests from conservation and Native Hawaiian activists who see telescopes there as an affront to the mountain, which Native Hawaiians hold sacred. Construction on the TMT ceased after protesters repeatedly blocked the road to the mountaintop; the conflict remains stalled and another site has been found and permits pulled for the Canary Islands. "If [Astro2020] says, 'Forget the ELTs; let's prioritize something else instead,' then it's quite possible that both the TMT and the GMT will die a financial death after having spent millions in start up costs," says a senior ground-based astronomer familiar with the deteriorating situation.
Astro2000's top-ranked space project, NASA's flagship James Webb Telescope, is a technological marvel: a cryogenically cooled infrared observatory with a uniquely segmented 6.5 m mirror that folds, origami-like, to fit in the nosecone of a multi-stage rocket. Following a staggering number of cost overruns, poor financial forecasts and delays that hobbled planning for other projects, the current best-case is that the telescope will reach space no sooner than this mid-November, if it does this year, operating for just a decade before it grows to war due to its loss of coolant, it'll have a total project cost of more than $10 billion.
If Webb retains the same hunger unleashed by Astro2000 and its antecedents gobbling off more than could be chewed, then the top flagship recommendation of Astro2010, NASA's the Nancy Grace Roman Space Telescope was a different animal entirely — a cut-rate cobbled together gizmo the Decadal committee put together willy-nilly from the piles of multiple competing mission concepts. Originally envisioned to study dark energy with a barebones instrument package and a mirror scarcely half the size of Hubble's, Roman was projected to launch as early as 2020 on a comparatively tight budget of less than $2 billion. To many expert eyes, such a cheap slap-dash project barely qualified for its supposed "flagship" status. NASA, hammered by bipartisan congressional blessings, ultimately added more instruments and upgraded Roman's mirror to the same size as Hubble's, enhancing its science objectives and assuaging many criticisms — but nearly doubling its estimated cost and setting back its launch to sometime around 2025.
And so this muddled mess is what passes for America's planned and unplanned ground and space based instruments for observing the universe for the next decade. Whoa. We'll have to bide our time to see what the Decadal Committee decides to do next with our tax money.
Hartmann352
1 SEP 2021, 1:20 PM, BY DANIEL CLERY
The Giant Magellan Telescope (left) and the Thirty Meter Telescope, shown in artists’ concepts, are making a joint pitch for federal funding.GIANT MAGELLAN TELESCOPE/GMTO CORPORATION; TMT INTERNATIONAL OBSERVATORY
Roughly every 10 years since the 1960s, U.S. astronomers have provided a valuable show of consensus to U.S. funding agencies and Congress by agreeing on which questions and new facilities are critical to the field. But the current “decadal survey,” known as Astro2020 and scheduled to be published at any time, faces a particularly knotty question, one that could settle whether the United States stays in the front rank of ground-based observing. Should the National Science Foundation (NSF) come to the rescue of two struggling private projects to build giant optical telescopes in exchange for a chunk of observing time?
The future of the Giant Magellan Telescope (GMT)* and the Thirty Meter Telescope (TMT)** likely depends on whether the survey recommends that NSF spend what sources put at $1.8 billion to support a recently forged partnership between the projects. If it does, other proposals could lose out, such as a continent-spanning radio array and detectors for neutrinos and other cosmic particles. (Space missions are ranked separately.)
Understandably, astronomers are divided. The GMT-TMT proposal “is critical for the field to thrive,” says John O’Meara, chief scientist of the W. M. Keck Observatory. With Europe pushing ahead with its own giant telescope, “If a federal partnership does not happen, I believe that the U.S., which has been the international leader in the field of astronomy for a century, will pass that role on to Europe,” says Wendy Freedman of the University of Chicago. But Richard Ellis of University College London, former director of the Palomar Observatory, believes rescuing both telescopes would cost “too much money and would eclipse so many other things.”
For ground-based optical astronomers, giant telescopes with mirrors about 30 meters across are the obvious next step after the huge advances made with today’s 10-meter scopes. O’Meara says there is no other way to image an Earth-like planet around a red dwarf star, for example. “No matter how tricky you get, the laws of physics overrule you,” he says. “Aperture is king.”
Telescope designers have been planning such behemoths since the 1990s, and the European Southern Observatory is laying the foundations for its 39-meter Extremely Large Telescope (ELT) on the summit of Cerro Armazones in Chile, with first light due in 2027. But divisions over technology and funding have hampered the two U.S.-led projects. The TMT, to be built in Hawaii by the California Institute of Technology and the University of California (UC), will have a honeycomb mirror built of 492 hexagonal segments. In contrast, the GMT, led by the Carnegie Institution for Science, will arrange six 8.4-meter mirrors around a seventh, giving the Chile-based telescope an aperture of 24.5 meters. The projects had early talks about joining forces, but “there was no desire to abandon their telescopes,” Ellis says. “Once money started flowing, it was impossible to merge.”
The 2000 decadal survey rated a giant segmented-mirror telescope (essentially the TMT) as the No. 1 U.S. priority in ground-based projects. NSF started discussions with the TMT about partnership in the project, but backed away after the GMT objected. In the 2010 decadal a giant ground-based scope dropped to No. 3, behind a large survey telescope and an instrument innovation program—a decision that essentially killed federal involvement for another 10 years. “That really damaged the momentum of the project,” says Garth Illingworth of UC Santa Cruz.
Both projects set out to raise their own funds, but neither has sufficient money so far. The TMT has also faced continued opposition, including legal challenges, from Native Hawaiians to building such a large structure on Mauna Kea, which they consider sacred.
For the current decadal, the projects have finally united into a two-telescope package that would give all U.S. astronomers access to at least 25% of the observing time in exchange for the $1.8 billion (a figure that is not officially confirmed). This deal, dubbed US-ELT, would give U.S. astronomers an advantage over Europeans: front rank telescopes in both the Northern and Southern hemispheres. “The U.S. really does need [giant telescopes] to follow up on other investments on the ground and in space,” Illingworth says.
Those include the James Webb Space Telescope (JWST), set for launch later this year. The JWST should revolutionize astronomy by picking out objects including the earliest galaxies with its pin-sharp infrared eyes, but fine-grained spectrometers on the ground will be needed to follow up on some discoveries. Then there is NSF’s Vera C. Rubin Observatory in Chile, a survey telescope that from 2023 will carry out a census of the sky nearly every night, identifying thousands of objects demanding closer investigation. “It would be an admission of defeat to let Europe take over this area,” Illingworth says.
Others say the U.S. giants are too far behind to avoid that outcome, and the costs are prohibitive. “How can you make a sales pitch for two telescopes when the rest of the world has one?” Ellis asks. Astronomers also worry about the consequences of funding US-ELT for projects such as a next-generation upgrade of the Very Large Array Radio Telescope (ngVLA) in New Mexico into a continent-spanning network of 263 dishes. “The ngVLA is no silly idea, it’s something we must do,” O’Meara says. The science cases behind upgrading the IceCube Neutrino Observatory at the South Pole and building a next-generation detector for the cosmic microwave background radiation are similarly compelling.
The decadal may also decide that U.S. astronomy doesn’t need to pursue an endless quest for ever-greater expanses of glass on the ground. Some astronomers think the greatest potential for discovery lies in modest new telescopes, or upgrades of older ones, with multiobject spectrographs that can scrutinize thousands of objects at once. “It’s a different vision,” says Ray Carlberg of the University of Toronto, and one that requires a team-based approach more familiar to particle physicists. “So much more science can be done with large groups of collaborators working together on a range of projects,” says Jennifer Marshall of Texas A&M University, College Station, project scientist of the proposed Maunakea Spectroscopic Explorer.
The 20-strong decadal committee, after a delay of more than 6 months because of the COVID-19 pandemic, should soon deliver its verdict, bringing joy to some and misery to others. “You need really big pockets” to build giant telescopes, Carlberg says. “The only people who can build them now are nations or consortia of nations.”
See: https://www.science.org/content/art...pes-balance-u-s-astronomers-debate-priorities
* Light gathered by the Giant Magellan Telescope (GMT) from the edge of the universe will first reflect off of the seven primary mirrors, then reflect again off of the seven smaller secondary mirrors, and finally, down through the center primary mirror to the advanced CCD (charge coupled device) imaging cameras. There, the concentrated light will be measured to determine how far away objects are and what they are made of.
The GMT primary mirrors are made at the Richard F. Caris Mirror Lab at the University of Arizona in Tucson. They are a marvel of modern engineering and glassmaking; each segment is curved to a very precise shape and polished to within a wavelength of light—approximately one-millionth of an inch. Although the GMT mirrors will represent a much larger array than any telescope, the total weight of the glass is far less than one might expect. This is accomplished by using a honeycomb mold, whereby the finished glass is mostly hollow. The glass mold is placed inside a giant rotating oven where it is “spin cast,” giving the glass a natural parabolic shape. This greatly reduces the amount of grinding required to shape the glass and also reduces weight. Finally, since the giant mirrors are essentially hollow, they can be cooled with fans to help equalize them to the night air temperature, thus minimizing distortion from heat.
One of the most sophisticated engineering aspects of the telescope is what is known as “adaptive optics.” The telescope’s secondary mirrors are actually flexible. Under each secondary mirror surface, there are hundreds of actuators that will constantly adjust the mirrors to counteract atmospheric turbulence. These actuators, controlled by advanced computers, will transform twinkling stars into clear steady points of light. It is in this way that the GMT will offer images that are ten times sharper than the Hubble Space Telescope’s.
The location of the GMT also offers a key advantage in terms of seeing through the atmosphere. Located in one of the highest and driest regions on earth, Chile’s Atacama Desert, the GMT will have spectacular conditions for more than 300 nights a year. Las Campanas Peak (“Cerro Las Campanas”), where the GMT will be located, has an altitude of over 2,550 meters or approximately 8,500 feet. The site is almost completely barren of vegetation due to lack of rainfall. The combination of seeing, number of clear nights, altitude, weather and vegetation make Las Campanas Peak an ideal location for the GMT.
See: https://www.gmto.org/overview/
** The Thirty Meter Telescope is a new class of extremely large telescopes that will allow us to see deeper into space and observe cosmic objects with unprecedented sensitivity. With its 30 m prime mirror diameter, TMT will be three times as wide, with nine times more area, than the largest currently existing visible-light telescope in the world. This will provide unparalleled resolution with TMT images more than 12 times sharper than those from the Hubble Space Telescope. When operational, TMT will provide new observational opportunities in essentially every field of astronomy and astrophysics. Observing in wavelengths ranging from the ultraviolet to the mid-infrared, this unique instrument will allow astronomers to address fundamental questions in astronomy ranging from understanding star and planet formation to unraveling the history of galaxies and the development of large-scale structure in the universe.
The Thirty Meter Telescope will be the amongst the largest ground-based observatories in the world and will provide new observational opportunities in essentially every field of astronomy and astrophysics. Astronomers will pursue further advancement of our inderstanding in several key science areas, including:
- Spectroscopic exploration of the “dark ages” when the first sources of light and the first heavy elements in the universe formed;
- Exploration of galaxies and large-scale structure in the young universe, including the era in which most of the stars and heavy elements were formed and the galaxies in today’s universe were first assembled
- Investigations of massive black holes throughout cosmic time
- Exploration of planet-formation processes and the characterization of extra-solar planets
- Exoplanet discovery observations that push into the terrestrial-planet regime
See: https://www.ucobservatories.org/observatory/thirty-meter-telescope/
See: https://www.tmt.org/page/science-themes
In the quest for an Extra-Large Telescope (ELT), the U.S. has managed to produce two competing projects, the Thirty Meter Telescope (TMT) and the Giant Magellan Telescope (GMT). Both have received shortfalls in funding, and neither appears likely to begin operations before the decade is out; each might put the financial skids on the other. The TMT's early stages of construction on the Hawaiian volcano Mauna Kea — a site unrivaled for pristine views of the Northern Hemisphere sky — sparked protests from conservation and Native Hawaiian activists who see telescopes there as an affront to the mountain, which Native Hawaiians hold sacred. Construction on the TMT ceased after protesters repeatedly blocked the road to the mountaintop; the conflict remains stalled and another site has been found and permits pulled for the Canary Islands. "If [Astro2020] says, 'Forget the ELTs; let's prioritize something else instead,' then it's quite possible that both the TMT and the GMT will die a financial death after having spent millions in start up costs," says a senior ground-based astronomer familiar with the deteriorating situation.
Astro2000's top-ranked space project, NASA's flagship James Webb Telescope, is a technological marvel: a cryogenically cooled infrared observatory with a uniquely segmented 6.5 m mirror that folds, origami-like, to fit in the nosecone of a multi-stage rocket. Following a staggering number of cost overruns, poor financial forecasts and delays that hobbled planning for other projects, the current best-case is that the telescope will reach space no sooner than this mid-November, if it does this year, operating for just a decade before it grows to war due to its loss of coolant, it'll have a total project cost of more than $10 billion.
If Webb retains the same hunger unleashed by Astro2000 and its antecedents gobbling off more than could be chewed, then the top flagship recommendation of Astro2010, NASA's the Nancy Grace Roman Space Telescope was a different animal entirely — a cut-rate cobbled together gizmo the Decadal committee put together willy-nilly from the piles of multiple competing mission concepts. Originally envisioned to study dark energy with a barebones instrument package and a mirror scarcely half the size of Hubble's, Roman was projected to launch as early as 2020 on a comparatively tight budget of less than $2 billion. To many expert eyes, such a cheap slap-dash project barely qualified for its supposed "flagship" status. NASA, hammered by bipartisan congressional blessings, ultimately added more instruments and upgraded Roman's mirror to the same size as Hubble's, enhancing its science objectives and assuaging many criticisms — but nearly doubling its estimated cost and setting back its launch to sometime around 2025.
And so this muddled mess is what passes for America's planned and unplanned ground and space based instruments for observing the universe for the next decade. Whoa. We'll have to bide our time to see what the Decadal Committee decides to do next with our tax money.
Hartmann352
Facebook
Twitter
Instagram