A $1.6-billion spacetelescope that could reveal the nature of dark energy and identify Earth-likeplanets should be the top priority for astronomers and astrophysicists,according to a long-awaited report that lays out the pressing needs for thenext 10 years of space science.
The Wide-Field InfraredSurvey Telescope (WFIRST) would launch in 2020 as one of the next generation of telescopes that should target the early universe, search fornearby habitable planets and test the boundaries of fundamental physics,according to the Astro2010 DecadalSurvey by the National Academy ofSciences.
"During the last DecadalSurvey, exoplanets weren't a big element, and dark energy wasn't really a bigdeal," said Claire Max, an astronomer at the University of California inSanta Cruz and member of the Decadal Survey committee. "There are a wholelot of things that are really new."
The influential report setsa roadmap for scientific priorities and chooses the most promising telescopecandidates for 2012-2021. Space- and ground-based research projects aresplit among large, midsize and small categories, so that WFIRST with its almost5-foot (1.5-meter) field-of-view came in first within the large category ofspace projects exceeding $1 billion.
For comparison, NASA's nexthuge space observatory ? the infrared James Webb Space Telescope ? has anestimated cost of about $5 billion and is slated to launch in 2014. The iconic HubbleSpace Telescope, which was launched in 1990, has a total cost of more than $10billion including its construction, launch and 20 years of operations. Majorinterplanetary missions, like NASA's Cassini mission to Saturn and Galileomission to Jupiter, also carried billion-dollar costs.
Anew ground-based observatory that could scan the entire available sky every three nightstopped report's list of vital, large ground projects that exceed $135 million.The $465-million telescope, called the LargeSynoptic Survey Telescope, would scan each region of the sky 1,000 timesover 10 years with an almost 28-foot (8.4-meter) aperture from its location inChile. It is slated to see first light before the end of the decade.
Unlike past reports, this latest Decadal Survey considered the technologicalreadiness and cost risk of each project. It also looked at previously consideredprojects such as LSST, which had matured since the most recent survey in 2001 andhas now been dubbed the most "ready-to-go" among the ground projects.
New eyes in space
The report also found that itsExplorer program that has supported small- and medium-sized missions such as NASA'sWide- Field Infrared Survey Explorer (WISE) ranked second in priority for large-cost spaceprojects. The astrophysics component would receive an annual budget boost from$40 million to $100 million by 2015.
Third priority went to the LaserInterferometer Space Antenna that consists of three formation-flying spacecraftto detect long-wavelength ripples in the fabric of space-time. Such ripplesrepresent gravitational waves caused by events such as black hole mergers.
NASA would share $1.4billion of the $2.4 billion total cost, assuming the European Space Agencyjoined in the effort. A successful 2012 launch of Europe's LISA Pathfindermission could lead to a full-scale LISA launch by 2025.
Another internationalproject, the International X-ray Observatory, would deploy a multi-part X-raymirror with about 20 times more collecting area than any existing X-rayobservatory. Current estimates put NASA's share of the $5 billion cost at $3.1billion, with the rest split among ESA and the Japan Aerospace ExplorationAgency.
The report's committeesuggested that IXO could represent a promising top candidate for the nextDecadal Survey, but only if the cost for NASA came down below $2 billion.
Stargazers on the ground
Earth-based projects alsoreceived careful scrutiny. The Mid-Scale Innovations Program that focused onsmall- to medium-scale experiments and facilities received second priority forthe large ground projects.
Third priority went to a"Giant Segmented Mirror Telescope" in the 98-foot (30-meter) range.Such a telescope could have three times the diameter, 10 times thelight-collecting area and 80 times the near-infrared sensitivity compared toexisting telescopes, assuming that it used the adaptive optics technology whicheliminates the atmosphere's blur effect.
Several giant telescopes slatedfor development include the $1.1-billion Giant Magellan Telescope sited forChile, the $1.4-billion Thirty-Meter Telescope sited at Mauna Kea in Hawaii,and the European Extremely Large Telescope. The report's committee noted thatthe federal government can only afford to contribute to one of the two U.S.telescopes, and proposed that the National Science Foundation immediatelychoose one for future investment.
Finally, the reportdesignated an Atmospheric CerenkovTelescope Array as the fourth priority for large ground projects. Such atelescope would use large arrays of ground-based telescopes to detect blueflashes of Cerenkov radiation, which are caused by very high energy gamma-ray photons from cosmicsources smashing into the atmosphere.
A U.S. version of the arrayknown as the Advanced Gamma-ray Imaging System was considered too expensive atmore than $400 million, and so the report suggests that the U.S. join theEuropean Cerenkov Telescope Array to share in costs and operations.
Making it happen
Government funding mayremain one of the biggest uncertainties hanging over the report, despite theconsensus among astronomers and astrophysicists about their scientificpriorities.
"My concern is that ifthe federal budget remains very constrained, we won't be able to do any of thisstuff," Max told SPACE.com.
The report did include somecontingency planning about budgetary shortfalls and the projected availabilityof money from NASA, NSF and the Department of Energy. But Max pointed out thatthe numbers kept changing even as the committee worked on the report.
Still, she remainedoptimistic about not only the progress of the past decade, but also having theright instruments to make discoveries beyond what researchers know.
"This is a chance toexploit those [past discoveries] and still build enough general-purposefacilities so that you can find the big new things for the next decade,"Max said.
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