By Daniel Clery
With NASA’s huge James Webb Space Telescope coming together and due for launch in 2018, the agency has announced its next major astrophysics project: another telescope known as the Wide-Field Infrared Survey Telescope (WFIRST). With a field of view more like a searchlight compared with Webb’s laser beam, WFIRST will aim to better understand the mysterious dark matter that holds galaxies together and dark energy that is speeding the expansion of the universe. In addition, it will be equipped to directly image planets around other stars.
“This mission uniquely combines the ability to discover and characterize planets beyond our own solar system with the sensitivity and optics to look wide and deep into the universe in a quest to unravel the mysteries of dark energy and dark matter,” John Grunsfeld, head of NASA’s Science Mission Directorate in Washington, D.C., said in a 17 February statement.
WFIRST was identified by astronomers at the top priority space mission in the 2010 decadal survey compiled by the National Academies of Sciences, Engineering, and Medicine. But its development has been in a state of suspended animation for several years because of cost overruns on Webb. The delay had an upside, however: In 2012 the U.S. National Reconnaissance Office gave NASA a pair of unwanted 2.4-meter mirrors designed for spy satellites. These were larger than what was planned for WFIRST, but design studies showed that, without the cost of grinding new mirrors, the spacecraft could be enlarged to accommodate one of them at no extra cost.
The new mirror also added extra capabilities: The mission had originally been planned as a dark energy mission, but the new optics would allow direct imaging of exoplanets with the addition of a coronagraph—a mask to block out the light from a star so that planets around it can be seen more easily. In addition to exoplanets studies, WFIRST’s wide field of view—100 times that of the Hubble Space Telescope—will allow it to measure the shapes, positions, and distances of millions of galaxies so as to understand the dark matter that facilitated their creation and how dark energy has affected cosmic expansion.
Not long ago, NASA officials had not expected to get WFIRST rolling until next year at the earliest. But lawmakers in Congress had pushed for a faster pace, adding money to NASA’s budget in recent years for planning and design. This past December, Congress approved a 2016 spending plan that included $90 million for work on WFIRST, along with orders to officially move the project forward early in 2016. NASA’s Program Management Council took that step on 17 February, with a view to launching the instrument in the mid-2020s. The next steps will be to come up with a formal schedule and cost estimate for WFIRST, which is expected to cost more than $2 billion.
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