NASA is initiating mission concept studies for a new generation of large space-based astrophysics observatories that could be considered during the next astrophysics Decadal Survey by the National Academies of Sciences, Engineering and Medicine. NASA astrophysics division director Paul Hertz outlined the concepts during a hearing before two House Science, Space, and Technology (SS&T) subcommittees today.

Decadal Surveys are conducted by expert committees organized by the Academies approximately every 10 years (a decade) to identify the most important scientific questions to be answered in the next 10 years and missions to obtain those answers. They are done for each of NASA’s space and earth science disciplines and in some cases for other agencies as well. The astrophysics Decadal Surveys makes recommendations for NASA as well as the National Science Foundation (NSF), which manages ground-based astronomy programs, and the Department of Energy’s high energy astrophysics programs.

Congress and the government agencies rely heavily on Decadal Surveys because they represent a consensus of the relevant scientific community. The first Decadal Survey was conducted in 1964 for the field of astronomy and astrophysics. Surveys for planetary science, solar and space physics (heliophysics), earth science and applications from space, and biological and physical sciences in space began more recently. Congress mandated in the 2005 NASA authorization act that the Academies also conduct mid-term assessments half-way through each respective decade to report on how the agencies are implementing the recommendations. The most recent astrophysics Survey — New Worlds, New Horizons — was issued in 2010 and its associated mid-term review is expected to be released soon.

Today’s hearing before the Space Subcommittee (which oversees NASA) and the Research and Technology Subcommittee (which has oversight of NSF) was focused broadly on astronomy, astrophysics and astrobiology, but much of the discussion was about NASA and NSF implementation of the 2010 Survey and plans for the next one.

Hertz told the subcommittees that NASA is looking at four potential large missions to follow the James Webb Space Telescope, scheduled for launch in 2018, and the Wide-Field Infrared Space Telescope (WFIRST) now in formulation in response to the 2010 Survey. He described the four concepts and the types of discoveries they could enable as follows:

the X-ray Surveyor that “might discover the first generation of supermassive black holes in the infant universe, unravel the structure of the cosmic web and determine its impact of the evolution of galaxies, and determine the influence of dark matter on the evolution of the universe”;

that “might discover the first generation of supermassive black holes in the infant universe, unravel the structure of the cosmic web and determine its impact of the evolution of galaxies, and determine the influence of dark matter on the evolution of the universe”; the Far-Infrared Surveyo r that “might find bio-signatures in the atmosphere of exoplanets…, map the beginnings of chemistry, and explain the origins of dust and the molecules that form the cradle of life”;

r that “might find bio-signatures in the atmosphere of exoplanets…, map the beginnings of chemistry, and explain the origins of dust and the molecules that form the cradle of life”; the Large Ultraviolet, Optical, and Infrared surveyor (LUVOIR) that “could be designed with a very large mirror that could capture the first starlight in the early universe, map the distribution of nearby dark matter with unprecedented resolution, detect water worlds and biomarkers on distant Earth-like planets, and image icy plumes from the moons of giant planets in our solar system”; and

that “could be designed with a very large mirror that could capture the first starlight in the early universe, map the distribution of nearby dark matter with unprecedented resolution, detect water worlds and biomarkers on distant Earth-like planets, and image icy plumes from the moons of giant planets in our solar system”; and the Habitable Exoplanet Imaging Mission (HabEx) that “could search for signs of habitability in the atmospheres of exoplanets.”

Exoplanets are planets orbiting other stars. NASA’s Kepler Space Telescope has identified over 5,000 exoplanet candidates so far.

Decadal Survey committees typically seek input from the scientific community at large for new mission concepts and Hertz made clear that these are only NASA’s concepts. Others may well emerge during the Survey process. Also, those are candidates for large missions only. NASA intends to retain a balanced portfolio of small, medium, and large missions.

Congress established the interagency Astronomy and Astrophysics Advisory Committee (AAAC) to coordinate activities across NSF, NASA and DOE in the 2002 NSF Authorization Act. Angela Olinto, a professor of astronomy and astrophysics at the University of Chicago’s Fermi Institute, currently chairs AAAC and also was a witness at today’s hearing. She praised the Decadal Survey process as the best way to prioritize missions based on cost and the availability of technology. She noted that her own project came in fourth in the last Survey and therefore did not make the cut, but she still believes Surveys are “the right process.”

Christine Jones, President of the American Astronomical Society and a

Senior Astrophysicist with the Smithsonian Astrophysics Observatory, similarly praised the community-driven Decadal Survey process and other mechanisms to obtain input from the broad astrophysics community. She noted that the four mission concepts described by Hertz originated in NASA’s three astrophysics Program Analysis Groups (PAGs), which also are community-driven.

NSF’s Director of the Division on Astronomical Sciences, Jim Ulvestad, said that NSF also follows the Decadal Surveys closely. It is currently building the Large Synoptic Survey Telescope (LSST) in response to the 2010 Survey. Implementing Survey recommendations can be a challenge because Survey committees must make assumptions about how much money will be available to execute the missions they recommend, but actual budgets may not match expectations. He said Surveys should be “aspirational” and “reach for the stars,” but not present a laundry list of missions that cannot be implemented.

Rep. Suzanne Bonamici (D-OR) asked about international cooperation and Hertz replied that 80 percent of NASA’s astrophysics missions are international partnerships. All four of the mission concept studies assume international collaboration and NASA is talking with the European Space Agency about participating in its ATHENA X-ray observatory and a possible future space-based gravitational wave detector.

NSF operates the Arecibo radio telescope in Puerto Rico, which NASA uses to characterize and track asteroids as part of its Near Earth Object Observation program. The fate of Arecibo has been uncertain for many years and NSF is again considering whether to continue funding it. Rep. Dana Rohrabacher (R-CA), who advocates for programs to defend Earth from potentially hazardous asteroids, asked whether NSF was about to “mothball” Arecibo. Ulvestad said no decisions have been made yet and stressed that, with regard to asteroids, Arecibo is used only to characterize and track known asteroids, not to find new ones that might threaten Earth. LSST is a survey telescope with a wide field of view that will be able to locate asteroids, he added, but Rohrabacher insisted that until LSST is operational, Arecibo is needed.

Olinto’s main message was that rising costs to operate astrophysics facilities coupled with constrained budgets is reducing the number of grants that can be approved. She said the number of successful grant applications has fallen from 30 percent to 20 percent. That reduces the number of graduate students that can be funded, affecting the next generation of astronomers and astrophysicists.

The importance of contributions to astronomy through observations by amateur

astronomers was highlighted by several committee members and witnesses. AAS’s Jones said that 250,000 college students enroll in introductory astronomy courses, 10 percent of the student population, an indication of the broad interest in understanding the universe.

Shelley Wright, a member of the advisory committee for the Breakthrough Listen project talked about public engagement in the Search for Extraterrestrial Intelligence (SETI). She said enthusiasm for SETI has increased dramatically, but resources are scare. While most SETI searches have been in the radio wavelengths, optical and infrared lasers might be better suited for the task. House SS&T committee chairman Lamar Smith (R-TX) lamented that NASA does not fund SETI searches.

NASA has not funded SETI searches since the early 1980s when Senator William Proxmire (D-WI), who chaired the appropriations subcommittee that funded NASA at the time, prohibited it because he considered it a waste of taxpayer dollars.

Rep. Brian Babin (R-TX) asked about potential use of the Space Launch System (SLS) and Orion spacecraft for future space-based astrophysics missions. He postulated that Orion crews might be able to service JWST, for example, as shuttle crews did for the Hubble Space Telescope. Hertz and Olinto acknowledged that SLS could enable launching much larger (in mass and size) space telescopes, but Olinto was not persuaded that astronauts could service JWST or other telescopes so far from Earth. Hubble is in Earth orbit and was comparatively easy to access with the shuttle. JWST will be at the Sun-Earth L2 Lagrange point. She suggested that robotic servicing was a more likely option, but the real key is to ensure that it is working properly before launch so servicing is not required.