NRC Concerned About Cost Implications of Changing WFIRST Design

NRC Concerned About Cost Implications of Changing WFIRST Design

A National Research Council (NRC) report released today lauds the additional science that could be obtained using hardware transferred to NASA from the National Reconnaissance Office (NRO) for the next large space telescope, but worries about the cost and potential impact on the balance of programs within NASA’s astrophysics portfolio, especially if a coronagraph is added.

NASA asked the NRC to look at the pros and cons of using the NRO hardware, which NASA refers to as AFTA (Astrophysics  Focused Telescope Assets) to meet the science objectives envisioned for the Wide Field Infrared Space Telescope (WFIRST).   WFIRST has a three-fold purpose: study dark energy, search for exoplanets, and survey the universe in the infrared wavelengths.

The NRC recommended WFIRST as the top priority for the next large space telescope after the James Webb Space Telescope (JWST) in its most recent Decadal Survey for astronomy and astrophysics, New Worlds, New Horizons (NWNH).  Cost growth and schedule delays in the JWST program – now scheduled for launch in 2018 – meant that substantive work on WFIRST will not begin for several years longer than envisioned when the NWNH Decadal Survey was published in 2011.

The version of WFIRST recommended in the NWNH Decadal Survey would use a 1.5 meter mirror, although a subsequent interim design reference mission (IDRM) reduced that to 1.3 meters.  In the meantime, however, NRO, which builds and operates the nation’s spy satellites, decided it no longer needed two space-qualified 2.4 meter mirrors and transferred them to NASA.   The agency is considering how best to make use of them.  Some scientists also now want to add another instrument– a coronagraph – to whatever new large space telescope is built.

According to today’s report, NASA told this NRC committee, chaired by CalTech’s Fiona Harrison, that implementing WFIRST with a 1.3 meter mirror is no longer under consideration.

The Harrison committee was tasked not with comparing that version with a new design utilizing NRO’s hardware, referred to as WFIRST/AFTA, but with evaluating how WFIRST/AFTA responds to the scientific objectives expressed in the NWNH Decadal Survey.  The committee also was asked whether a coronagraph would advance technology development and scientific goals expressed in the Decadal Survey.

The Harrison committee concluded that WFIRST/AFTA would “significantly enhance the scientific power of the mission, particularly for cosmology and general survey science,” and benefit the search for exoplanets.   However, it also found that using the AFTA hardware could add to the program’s cost:  “The use of inherited hardware designed for another purpose results in design complexity, low thermal and mass margins, and limited descope options that add to the mission risk.  These factors will make managing cost growth challenging.”

As for adding a coronagraph, the Harrison committee was less than enthusiastic because its design is “immature” and could further add to the technical risk and potential cost.  The committee stressed that it was “the moderate cost, low technical risk and mature design” of the original WFIRST concept that led the Decadal Survey committee to make it the top priority.  Therefore, “inclusion of the coronagraph compromises this rationale.”

A prominent theme in today’s report is a reminder that the fundamental tenet of the NWNH Decadal Survey is to maintain balance in NASA’s astrophysics portfolio among large programs like WFIRST, smaller programs in the Explorer series, and the associated Research and Analysis (R&A) program   “If implementing WFIRST/AFTA compromises the program balance then it is inconsistent with the rationale that led to the high priority ranking,” the Harrison committee warned.

NASA needs to “mature the coronagraph design and develop a credible cost, schedule, performance, and observing program” before the impact of adding such an instrument to WFIRST can be determined, the Harrison committee determined.  Once that is done, NASA should convene additional independent reviews of the coronagraph and of whatever mission design NASA ultimately proposes as a new start “to ensure that the proposed mission cost and technical risk are consistent with available resources and do not significantly compromise the astrophysics balance” recommended by the Decadal Survey.

Congress appropriated $668 million for NASA’s astrophysics program for FY2014 (which is separate from the funding for JWST), an increase of $46 million above the $622 million requested.  It then directed NASA to use $56 million of its FY2014 astrophysics funding to proceed with design studies, technical risk reduction and mission formulation to meet the exoplanet and dark energy objectives of WFIRST.  NASA’s FY2014 operating plan, which provides details of how it plans to spend its FY2014 appropriations, has not been made public, so details on how it will spend that  $56 million are not available yet.

Note:  the original version of this story said that the 1.3 meter mirror was recommended in NWNH, but it recommended a 1.5 meter mirror.  The 1.3 meter mirror resulted from a subsequent interim design reference mission (IDRM).


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