Ever since it was revealed on Monday that a US spy agency would be bequeathing to NASA not one but two telescopes at least as good as the Hubble space telescope (pictured), astronomers have been licking their chops. Here was a chance to resurrect WFIRST, a mission that would seek a better handle on dark energy, which is speeding up the expansion of the Universe. The 2.4-metre-wide telescopes have a field of view much wider than Hubble’s and would be better suited to the survey approach called for in WFIRST. “It’s a tremendous opportunity,” says David Spergel, an astronomer at Princeton University in New Jersey and co-chair of a National Academies committee that was meeting this week when the news was revealed.
But on Tuesday, NASA was still keeping relatively quiet about the apparent windfall. “We’re not pushing this information like we normally do,” said Michael Moore, NASA’s acting deputy director for astrophysics.
Why wouldn’t NASA be trumpeting this news from a mountaintop? One answer is that the telescopes, each valued by NASA at around US$250 million, might actually make a WFIRST mission more expensive. After all its troubles with the James Webb Space Telescope — which ballooned in costs to $8.8 billion and is the main reason a WFIRST mission has been put off — the agency doesn’t want to make a similar mistake. Spergel acknowledges that, paradoxically, the gift might in fact make WFIRST more expensive. “It enables you to do WFIRST faster, it enables you to do it better,” he says. “But I don’t think we know yet if it lets you do it cheaper.”
‘Faster’ and ‘better’ are easy to explain. Construction of the mirror of any space telescope is work that often has to begin the soonest — a so-called “long-lead” item. As it stands right now, NASA would not be able to launch WFIRST until 2024. Moore says that, with an infusion of money to repurpose one of the spy telescopes, a WFIRST launch could happen as early as 2020.
‘Better’ is also relatively obvious. WFIRST, as evaluated by the decadal survey in 2010, was designed around a 1.5-metre mirror. Bumping that up to 2.4 metres means that the mission can peer deeper into the Universe. It also means that it can survey the sky much more quickly. Furthermore, a 2.4-metre telescope is big enough to capture the attention of exoplanet hunters. Some are already calling for a star-blocker to be added to the guts of telescope, so that the faint light of planets might be seen.
But WFIRST was already estimated to cost $1.6 billion when it was going to be squeezed onto the 1.5-metre telescope. Reconfiguring the mission for the larger 2.4-metre telescope will come with added expenses. The spy telescopes currently contain only the mirrors, optics and other structural supports; they lack solar panels, instruments and electronics — which are apt to be more expensive than for a 1.5-metre telescope. A heavier telescope would also require a more expensive rocket to lift it into orbit.
On the other hand, Spergel points out that doing something faster — launching in 2020 rather than 2024 — means lowering the cost of telescope’s human overhead. The “standing army” associated with any project is often one of the biggest costs. Moore says that a new WFIRST based on one of the spy telescopes could cost between $1 billion and $2 billion. Whether the $250 million “gift” makes the true cost more or less than $1.6 billion remains to be seen. “I think we need a serious evaluation of the cost,” Spergel says.
Image credit: NASA