NASA’s WFIRST probe faces cost crisis

An illustration of the Wide-Field Infrared Survey Telescope WFIRST, which is scheduled to launch in 2025. Credit: NASA GSFC/CI Lab.

There is a new major space observatory by NASA to be launched in 2025, that is The Wide-Field Infrared Survey Telescope (WFIRST) and is meant to tackle some of the biggest questions in astronomy such what exoplanets look like and how dark energy is driving the Universe’s expansion. 

Now the WFIRST project has grown in scope and complexity since it was proposed nearly a decade ago, and its price has swollen from US$1.6 billion in 2010 to the current estimate of $3.2 billion ($2.4 billion in 2010 dollars). Unsurprisingly it has raised concern at NASA, which in April commissioned a review by independent aero-space experts. Their report is due in the next few months.

NASA wants to avoid the path of the James Webb Space Telescope (JWST), the successor to the Hubble telescope, and scheduled to launch in 2018. That particular project’s cost rocketed from a 1 billion $US in the early 2000s to 8.8 billion $US. In order to prevent that situation NASA has issued The WFIRST review. 

The Astronomy and Astrophysics Decadal Survey made WFIRST a the top-ranked big space mission back in 2010, and later the National Reconnaissance Office gave this NASA project a 2.4-metre mirror, an upgrade from the original planned 1.5-metre mirror, making possible for NASA to add a corona-graph, an instrument that studies exoplanets by blocking light from the stars they orbit.

So NASA made other design changes to go along with the now bigger mirror. It began to consider adding a ‘starshade’, a free-floating umbrella-like spacecraft that would fly alongside WFIRST and block enough light for the telescope to spy Earth-sized planets.

The core of WFIRST is a gigantic camera with 18 detectors, each capable of capturing a 16-mega-pixel shot giving it a field of view 200 times Hubble’s. “When you have this enormous field of view you can address scientific problems that really are not practical with missions like Hubble or Webb,” says Jeffrey Kruk, the WFIRST project scientist at the Goddard Space Flight Center in Greenbelt, Maryland.

The wide field imaging capability of WFIRST enables large area surveys at a much faster rate but at the same resolution as HST/WFC3/IR. The HST/WFC3/IR PHAT Survey required 432 pointings to cover M31 while only 2 WFIRST pointings are required. Credit: NASA.

Thus allowing WFIRST to tackle tasks such a survey to measure how the structure of the Universe evolved over time, which will shed light on the nature of dark energy. WFIRST’s data should complement the observations of several other dark-energy explorers set to come online in the early 2020s, such as the European Space Agency’s Euclid probe, says Rachel Mandelbaum, an astrophysicist at Carnegie Mellon University in Pittsburgh, Pennsylvania.

Regarding the exoplanet studies that can be achieved by WFIRST include hunting indirectly for planets in the bulge of stars at the centre of the Milky Way, and imaging others directly using the coronagraph. The coronagraph is meant to demonstrate technologies for future missions, but should also be able to photograph Neptune-sized planets. “We really hope and expect to do revolutionary exoplanet science,” says Jeremy Kasdin, a technologist and engineer at Princeton University in New Jersey who leads the coronagraph team.

However, there is only so much money to put towards all these goals. Last August, a review of NASA’s progress towards its 2010 decadal priorities singled out WFIRST as at risk of ballooning costs. The review cited the cost of the coronagraph — which a different panel estimated at around US$350 million — and design changes that added another US$550 million.

WFIRST Observatory Concept. Credit: NASA.

The new study will help NASA evaluate how to preserve as much of WFIRST’s scientific capability as possible while remaining within budget, says John Gagosian, the mission’s programme executive at NASA headquarters in Washington DC. But he sees no reasonable scenario “in which the current mission scope and requirements (including the coronagraph) can be implemented for US$3.2 billion or less”.

One potential cut would be to eliminate the coronagraph or to pare back its capabilities. Another would be to trim the number of detectors on the wide-field camera, or the amount of time dedicated to the dark-energy survey.

Whether such belt-tightening is enough to keep WFIRST under US$3.2 billion is unclear. A way to save money year-to-year would be to stretch the project’s lifespan, says Kruk — but that increases the total cost. And launching it later than 2025 would cut back on the mission’s chance to overlap with the JWST and find rare celestial objects that that telescope could then study in detail.

The next major milestone for WFIRST will come after the review panel submits its recommendations. Late this year or early next, programme managers will decide what they may need to strip off the spacecraft to keep the project alive.

Sources: Nature, Alexandra Witze, NASA, ESA, arXiv, Wikipedia,