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Understanding Dark Energy, Finding Earth-like Planets Top Priorities Says NRC's Astro2010 Study

Marcia S. Smith
Posted: 13-Aug-2010
Updated: 05-Dec-2011 06:17 PM
The National Research Council (NRC) released its most recent Decadal Survey for astronomy and astrophysics today. Formally entitled New Worlds, New Horizons in Astronomy and Astrophysics, but dubbed "Astro2010," the report lays out the scientific and mission priorities for ground- and space-based astronomy for the next 10 years. It is the sixth NRC Decadal Survey in this field; the first was issued in 1964. Decadal Surveys are so-named because they are conducted about every 10 years - a decade - and look forward to the next decade of research. (For more on the NRC and Decadal Surveys, visit the National Research Council page on our left menu at SpacePolicyOnline.com.)

The Astro2010 study committee divided its recommendations into three categories of missions: large, mid-sized, and small. For space-based missions, the committee identified a Wide-Field Infrared Survey Telescope (WFIRST) as the top priority for large missions. A collaboration between NASA and the Department of Energy (DOE), it would answer questions about dark energy, determine the likelihood of other Earth-like planets, and conduct other research about the galaxy. The top priority for the ground-based astronomy program is the Large Synoptic Survey Telescope (LSST), which also would study dark energy, as well as dark matter, time-variable phenomena, supernovas, Kuiper-belt and near-Earth objects. That project would be a collaboration between the National Science Foundation (NSF) and DOE.

The study committee was chaired by Prof. Roger Blandford of Stanford University. It created a set of science panels to identify key science questions and then a set of program panels to recommend ground- and space-based missions to answer them. The three key scientific objectives they identified were deepening our understanding of how the first stars, galaxies and black holes formed; locating the closest habitable Earth-like planets; and using astronomical measurements to "unravel the mysteries of gravity and probe fundamental physics," according to an NRC press release.

For space missions, the committee also emphasized the importance of Explorer-class missions; the Laser Interferometer Space Antenna (LISA) to search for gravity waves from the Big Bang; and the International X-Ray Observatory. They are the second, third and fourth priorities, respectively, for large space-based missions.

The top priority for mid-sized space missions is a New Worlds Technology Development mission to provide the scientific basis for a future mission to study nearby Earth-like planets.

Understanding dark energy - "dark" because scientists do not understand what it is - has become a compelling field of scientific research. In the mid-1990s, scientists discovered that the universe is expanding more rapidly than theorized and they don't know why. They invented the term "dark energy" to refer to the unknown energy force that is causing the accelerated expansion rate. Data from NASA's Wilkinson Microwave Anisotropy Probe (WMAP) led scientists to conclude that the universe is composed about 4.6% of atoms, 72% of dark energy, and 23% of "dark matter" - another unknown phenomenon. That means that they understand only 4.6% of the universe and the rest is unknown dark energy and dark matter.

NASA and DOE had been planning a Joint Dark Energy Mission (JDEM) that was controversial because the agencies had different approaches to studying it and funding was limited. NASA grouped it into a class of missions called "Beyond Einstein" to understand the fundamental physics of the universe. A 2007 NRC report picked JDEM as the top priority of the five Beyond Einstein missions. The Astro2010 report preserves dark energy as a top priority. The report says that WFIRST is based on a JDEM proposal ("JDEM Omega") developed in collaboration between NASA and DOE. and will also search for exoplanets, including Earth-like planets, and perform other research in infrared wavelengths.

NASA is currently building an infrared telescope called the James Webb Space Telescope (JWST) as a follow-on to research conducted with the Hubble Space Telescope, though Hubble primarily looks at the universe in visible wavelengths rather than infrared. At $5 billion, JWST is over budget and behind schedule. Its current launch date is 2014, but that may slip because of recent cost increases. The new WFIRST telescope also would be infrared, but is a wide-field instrument rather than a targeted telescope like JWST. "The small field of view of JWST would render it incapable of carrying out the prime WFIRST program of dark energy and exoplanet studies, even if it were used exclusively for this task," according to the Astro2010 report.

This is the first NRC Decadal Survey required to obtain independent estimates of the cost and technical readiness of its proposed missions. Previous Decadal Surveys were criticized because their cost estimates often turned out to be unrealistically low. The NRC does not have the capability to do cost estimating and had relied on the teams proposing a mission to provide cost estimates. For NASA-related missions, "independent" cost analysis was often performed by NASA centers and did not sufficiently take into account so-called "unknown unknowns" that often add to a project's cost. In addition, missions recommended in Decadal Surveys often changed substantially as they went through the development process and while they retained the same name, the scope and complexity often increased, further adding to the costs.

Section 1104 of the 2008 NASA Authorization Act directed NASA to contract with the NRC to conduct Decadal Surveys and as part of those efforts for the NRC to obtain independent estimates of life cycle costs and technical readiness whenever possible. For Astro2010, the NRC created a Cost, Risk and Technical Evaluation (CATE) process that involved hiring a contractor, the Aerospace Corporation. The report emphasizes that the contractor operated independently of the committee "so that their final analysis was free from undue influence by either the committee itself or by interests outside the [decadal] survey.....[W]hile the committee worked closely with the contractor ... the final result has been accepted and certified as independent work performed by the contractor alone. Equally important to the independence of the contractor is the committee's responsibility for reviewing the contractor's work and exercising its judgment in accepting the contractor's results."

WFIRST has an estimated cost of $1.6 billion between 2012 and 2021, with launch expected in 2020 if the project begins in FY2013. There is a possibility that the United States will cooperate with the European Space Agency (ESA) on this mission. ESA is planning its own dark energy mission, Euclid. LSST, which would be located in Chile, is estimated at $465 million for 2012-2021 with annual operating costs of $42 million, of which the Federal share is $28 million. Costs are in FY2010 dollars.

NASA, NSF, and DOE funded the study, which was conducted under the auspices of the NRC's Board on Physics and Astronomy and Space Studies Board.


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