NASA Presses Case for Euclid with Space Astronomers

NASA Presses Case for Euclid with Space Astronomers

NASA continued to woo the U.S. space astronomy community today hoping that it will agree to NASA’s proposal to increase its potential participation in the European Space Agency’s (ESA’s) proposed Euclid mission from 20 percent to 33 percent. The second day of discussion at the NASA Advisory Council’s (NAC’s) Astrophysics Subcommittee meeting reiterated many of the points from yesterday, but participants were joined today by NASA Associate Administrator for Science Ed Weiler. They also were briefed by phone by ESA’s Fabio Favata on ESA’s process for choosing science missions and where they stand today. Euclid is one of three ESA missions vying for two spots in ESA’s science program; a decision will be made next summer.

NAC astrophysics subcommittee members are chosen by NASA to represent the broad space-based astrophysics community and they expressed a wide range of views about the wisdom of U.S. participation in Euclid and at what level. Euclid would search for answers to the mystery of dark energy, an unknown force accelerating the expansion of the universe. The recent U.S. National Research Council Decadal Survey for astronomy and astrophysics, Astro2010, identified a multidisciplinary project, WFIRST, as its top priority for space missions. WFIRST also would study dark energy, along with searching for earth-like planets (exoplanets) and performing an infrared sky survey. Astro2010’s top priority for ground-based astronomy, the Large Synoptic Survey Telescope (LSST), also would search for dark energy.

Many subcommittee members wondered why NASA would support two space missions that they view as having very similar science objectives when resources are so constrained. ESA-NASA discussions prior to the release of Astro2010 centered on NASA participating in Euclid at a 20 percent level, but more recently the two agencies have been discussing a 33 percent U.S. share. That would cost NASA $260 million over 10 years according to Dr. Weiler.

He and Jon Morse, Director of NASA’s Astrophysics Division, tried to downplay that amount, saying it was only $26 million per year, but subcommittee members clearly viewed it as a threat to funding for technology development or other activities. Several subcommittee members were inclined to limit NASA participation in Euclid to a minimum level. Others wanted more NASA participation, perhaps even a merging of Euclid and WFIRST with the two agencies sharing the costs on a roughly equal basis.

Dr. Weiler reminded them of the history of NASA-ESA discussions about working together on a dark energy mission. He said that two years ago, the agencies agreed to cooperate on a program where the United States would have had the lead in the program, but the plan was scuttled because “some people in the community didn’t like that.” At the time, NASA was working with the U.S. Department of Energy (DOE) on the Joint Dark Energy Mission (JDEM) and his reference may have been to members of that community, although he was not specific.

In any case, he emphasized that ESA now is well along in its planning for Euclid and does not want to make any major changes – like adding new requirements – lest the mission lose its place in the ongoing selection. Increasing the U.S. share to 50 percent was suggested to ESA recently, he said, and rejected. He spelled out two options for the space astronomy community: 33 percent participation in Euclid, which would put four U.S. scientists on the program’s science definition team and give them access to data about dark energy in 2018 when the probe is launched; or no participation in Euclid and U.S. scientists would have to wait until 2022, the notional launch date for WFIRST under NASA’s budget assumptions, for dark energy data. After spirited repartee with committee members, he added a third option, to keep U.S. participation at the 20 percent level.

Subcommittee discussions are continuing, but they have little time to reach agreement on what to recommend to their parent NAC Science Committee, which meets on September 28. Dr. Weiler and Dr. Morse told them they need an answer by the end of this month. Dr. Weiler also noted that the astronomy community is not the only voice that needs to be heard. Congress, the Office of Management and Budget, and the Office of Science and Technology Policy all have a say, he stressed.

With only about $2 billion available for new missions in NASA’s astrophysics budget over the next decade, $260 million is a sizeable investment. Dr. Morse dangled the prospect of ESA contributing a like amount to WFIRST if an agreement can be reached, but that would not happen until at least next year so there are no guarantees. In fact, there is no guarantee that Euclid will even be picked by ESA, as the NASA officials repeatedly pointed out.

Astro2010 just set priorities for astronomy and astrophysics research for the next decade, but this issue of increasing U.S. participation in Euclid arose after its report was complete. Astro2010 chair Roger Blandford declined to hypothesize on what the Decadal Survey committee might have thought about increasing participation in Euclid, reminding the group that the study is completed and in any case only sets priorities. Implementation is NASA’s responsibility, he said. Yesterday he reminded the subcommittee about exactly what Astro2010 said about Euclid in the context of its WFIRST recommendation: “Collaboration on a combined mission with the United States playing a leading role should be considered so long as the committee’s recommended science program is preserved and overall cost savings result.”

U.S. leadership in dark energy research appears to be one of the factors in decisions about how to move forward. Although WFIRST is indeed the acronym for Wide Field InfraRed Survey Telescope, it could also be a play on words. The search for dark energy is in part a quest to measure a dark energy parameter designated “w.” WFIRST might then be taken to mean that U.S. astronomers want to be sure they are the first to determine the value of w. (An excellent discussion of dark energy and w can be found in a 2007 NRC report NASA’s Beyond Einstein Program: An Architecture for Implementation.)

Correction: an earlier version of this article misstated when the NAC Science Committee is scheduled to meet. Its next meeting is September 28, not next week. It will meet by telephone and WebEx; see our calendar on the right menu for a link to the Federal Register notice about the meeting. Also, the NRC Beyond Einstein report was published in 2007 not 2008 — how time flies!

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