WFIRST Passes its Preliminary Design Review

The telescope for a major NASA astrophysics mission has passed a key review that the agency says keeps it on track for launch in the mid-2020s despite uncertainty about its funding for 2020 and beyond.

NASA announced Aug. 28 that the telescope assembly for the Wide Field Infrared Survey Telescope (WFIRST) mission passed its preliminary design review (PDR), allowing the project to continue work to finalize its design.

WFIRST, scheduled for launch in the mid-2020s, is NASA’s next flagship astrophysics mission after the James Webb Space Telescope. The mission will use a 2.4-meter mirror provided to NASA by the National Reconnaissance Office. That mirror is currently being modified by L3 Harris Technologies for use on WFIRST.

The telescope will later be equipped with both a wide-field imager instrument and a coronagraph, which blocks light from stars to allow direct imaging of planets and dust disks orbiting them. Both will have their own preliminary design reviews, along with one for the entire mission.

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NASA Kicking off WFIRST Space Telescope in February

NASA’s next flagship astronomy mission after the James Webb Space Telescope will become a formal project in February thanks to increased funding and direction from Congress, even as the agency looks to make cuts elsewhere in its astrophysics program.

Paul Hertz, director of NASA’s astrophysics division, told astronomers attending the 227th Meeting of the American Astronomical Society here Jan. 4 that the Wide Field Infrared Survey Telescope (WFIRST) will enter its “formulation phase,” the beginning of NASA’s project management process, in February after the proposed space telescope passed a mission concept review in December.

That decision also comes after the passage of the fiscal year 2016 omnibus spending bill in December that provided $90 million for WFIRST, far above NASA’s request of $14 million. The report accompanying the bill adopted language approved by Senate appropriators in June directing NASA to move WFIRST into the formulation phase by early 2016.

The increase is not the first time Congress has added funding for WFIRST. In fiscal year 2015, NASA requested $14 million but Congress appropriated $50 million. In 2014, Congress provided $56 million for WFIRST.

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WFIRST Could Detect Kuiper Objects as Small as 7.5 km Diameter

WFIRST Ultra-Precise Astrometry I: Kuiper Belt Objects

Author:

Gould

Abstract:

I show that the WFIRST microlensing survey will enable detection and precision orbit determination of Kuiper Belt Objects (KBOs) down to H_vega=28.2 over an effective area of about 17 square deg. Typical fractional period errors will be ~1.5% X 10^{0.4(H-28.2)} with similar errors in other parameters for roughly 5000 KBOs. Binary companions to detected KBOs can be detected to even fainter limits, H_vega=29, corresponding to R~31 and effective diameters D~7.5 km. This will provide an unprecedented probe of orbital resonance and KBO mass measurements.

WFIRST Telescope Using ex NRO Hardware Greatly Increases Science...and Financial Risk

The opportunity to increase the aperture and resolution on NASA’s planned Wide-Field Infrared Survey Telescope (WFIRST) would significantly expand the scientific capabilities of the mission, but the risk of cost growth is significantly higher than for NASA’s original design, says a new report from the National Research Council.

WFIRST was ranked the top-priority large space mission in the National Research Council’s 2010 decadal survey of astronomy and astrophysics research. WFIRST would probe the nature of dark energy – the as yet unexplained driver behind the accelerating expansion of the universe; study the architecture of other solar systems; and advance understanding of how galaxies, stars, and black holes evolve. This science program, together with the mission’s moderate cost, low technical risk, and mature design were key factors in its top ranking among large space missions.

NASA initially considered a design of WFIRST with a 1.3-meter aperture. In 2012, the National Reconnaissance Office gave NASA hardware for two 2.4-meter telescopes -- the same size as the currently operating Hubble Space Telescope. NASA dubbed these the Astrophysics Focused Telescope Assets (AFTA) and began to study an alternative to the original telescope design. After the NRO telescopes were acquired, NASA also began to consider the addition of a coronagraph, an instrument that would advance goals in the study of exoplanets.

The new Research Council report compares the WFIRST/AFTA design both with and without a coronagraph to the original mission concept, on the basis of their science objectives, technical complexity, and programmatic rationale, including projected cost. The report does not recommend which design NASA should adopt.

The committee that wrote the report found that the larger aperture provided by the 2.4-meter design “will significantly enhance the scientific power of the mission” for cosmology, exoplanet surveys, and general infrared survey science, such that the mission is consistent with the scientific goals described in the decadal survey. This new design also makes inclusion of a coronagraph attractive.

However, the inherited hardware was designed for another purpose, and the degree to which changes to the hardware must be made to accommodate a different launch vehicle and scientific requirements is uncertain at this time. This uncertainty contributes to higher technical risk and a greater likelihood that costs will increase beyond current estimates, the report says. The WFIRST/AFTA without the coronagraph was estimated to cost $2.1 billion, up from an estimate of $1.8 billion for an earlier design which was more similar to the mission recommended in the 2010 survey report.

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