recommended in NWNH. More broadly, this budget situation has serious consequences for elements of the program that address time-critical science opportunities and strive for a balanced and diverse program.

As the panel heard from the survey chair at its workshop, key to the WFIRST mission recommendation is the possibility of its rapid development and thus launch within the decade.4 Current estimates of a launch of 2022,5 or even much later, substantially weaken NWNH’s rationale for this mission, and would also postpone the development of future missions (in the 2020-2030 time frame). NWNH states that WFIRST’s relatively low technical risk makes it “feasible to complete within the decade, even in a constrained budgetary environment. For these reasons [emphasis added], it is the toppriority recommendation for the space-based initiative” (p. 3-14). NWNH considered LISA and IXO to be compelling, highly capable, and more ambitious flagship missions than WFIRST but ranked them lower because of their required new technology development, higher cost, and technical risk, which, given NWNH’s budget assumptions, make launch this decade or even early next decade highly unlikely. If WFIRST development and launch are significantly delayed beyond what was assumed by NWNH, one of the key considerations that led to this relative ranking is no longer valid.

The panel notes that the NWNH program also includes (1) key investments in technology development for future missions, (2) medium-scale activities (beyond such technology development), and (3) small-scale activities, all of which are jeopardized by the austere budgets now under consideration. While the advantages of appropriating the projected budget scenarios utilized in developing the NWNHrecommended astrophysics program are obvious, the panel recognizes the unique challenges that this option presents. However, until the issues associated with WFIRST (and JWST) are clarified, it is difficult to determine whether the relative priorities of NWNH should be reconsidered, or whether resources would be better invested in small and medium-scale activities than on a significantly delayed WFIRST. The relative development schedules of Euclid and WFIRST may also be a factor in such considerations. Having heard the evidence presented at its workshop, the panel finds that the current situation is unclear and that all of these issues may well require consideration by the decadal survey implementation advisory committee (DSIAC) recommended in NWNH when more information is available. This panel, echoing the assumption in NWNH that the mission would be available to address key science priorities in the decade ahead, strongly emphasizes that the success of JWST is central to U.S. space astronomy, but hopes that whatever means are found to address the JWST cost increases do not vitiate the exciting program put forward in NWNH.

OPTION B: A JOINT WFIRST/EUCLID MISSION

If the budget constraints that have emerged since delivery of the NWNH report are not adequately addressed (see Option A) and a timely WFIRST as originally conceived is not possible, one option to accomplish WFIRST’s goals would be a single international mission, combining WFIRST and ESA’s Euclid.6 The panel affirms the scientific priority of a mission that accomplishes all the goals of WFIRST and that would also accomplish the goals of Euclid. Although no path has yet been identified by the agencies toward a single international mission, such a mission may still be possible. Fitting the ESA and NASA processes together at this stage would be a challenge, but the scientific benefits are clear. Were a joint mission to remain on the ESA schedule for Euclid to launch within this decade, it would indeed be completely consistent with the NWNH plan for WFIRST.

The NWNH report recommended a leadership role for the U.S. in a joint mission. The panel interprets “a leadership role”7 to mean (1) ensuring that the science requirements and observing plan, which are jointly designed and agreed upon, support all the primary WFIRST science goals specified in NWNH—namely, planet microlensing, dark energy science (through the BAO, weak lensing, and Type Ia

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4 As described in Roger Blandford’s presentation at the panel’s November 7, 2010, meeting.

5 As described by NASA at the panel’s November 7, 2010, meeting.

6 See number (3) in “Specific Statements in NWNH Concerning Euclid” above.

7 NRC, New Worlds, New Horizons in Astronomy and Astrophysics [prepublication], 2010, p. 3-14.



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