“I think that’s kind of a foolish approach because, heaven forbid, it’s possible that something could go wrong with James Webb,” Ellis says. “You should never wait for something that hasn’t been launched. Also, if you do ambitious work with Spitzer, you probably will learn something that will help you better utilize James Webb.” He’s wary that the run-up to the new telescope’s deployment will have a chilling effect on other observations. “As we get closer to the launch of James Webb, maybe even programs with Hubble will be deferred, which I think would be a shame.”
While the Webb telescope will be, in Berta-Thompson’s words, “an excellent, all-purpose, figuring-things-out machine,” astronomers did not get everything on their wish list. “I guess if I had my druthers, I would optimize things a little bit better for studying very bright targets,” Berta-Thompson says. Astronomers who focus on distant galaxies at high redshift, however, like Lilly does, approve of Webb’s optimization for faint objects. But even they can’t have everything. “I was sad when the mirror went down from eight meters to six and a half many years ago,” before the contract with Northrop Grumman was finalized in 2002, Lilly says.
Lilly points out that one project he was involved with, the Cosmic Evolution Survey (COSMOS), was the longest observation ever to win time on Hubble. Creating a deep mosaic of visible light in a two-degree region of the sky, using Hubble’s Advanced Camera for Surveys, took 640 orbits—about 1,000 hours—over two years. “If Hubble had had instruments with a field of view twice as large, it would’ve taken half as much observing time,” he says. “Ironically, the decision to halve the field of view on [Webb’s Near-Infrared Camera] was taken at almost exactly the same time” as COSMOS’s findings demonstrated the value of a more capable near-infrared camera for the observatory. “What can I tell you,” Lilly sighs. “That was unfortunate.”
He recognizes that compromises between cost and capability must be made. “One of the things which has been said which is not true about Webb is that there has been capability creep—that the astronomers always wanted more,” he says. “From my perspective, that hasn’t happened.... Often capabilities which one would’ve liked to have had were reduced.”
Ellis thinks that one element that has contributed to concern over the Webb telescope’s cost is the lingering memory that Hubble’s mirror turned out to be shaped incorrectly, a fact that went unnoticed until after its launch. Only after the first servicing mission, in December 1993, three years after the launch, when astronauts installed a pair of corrective optical devices, was Hubble able to realize its potential. In its L2 orbit, Webb will be four times as distant from Earth as the moon, beyond the reasonable reach of manned repair should something go wrong.
But Menzel points out that building something to be effectively unbreakable within its planned life is the rule, not the exception. “The truth is, for almost 50 years, the majority of spacecraft we launch have not been serviceable,” he says. “And they’ve lasted perfectly fine without servicing.”
Still, the Webb telescope has a lot to prove. Its cost has taken money away from other NASA science projects; it’s years behind its original schedule and vastly complex, and if something goes wrong, it would be a bust. Phil Plait, once an astronomer who got observing time on the Hubble telescope, now writes a popular column for Slate called “Bad Astronomy.” He echoes a common refrain from astronomers: Hubble also took longer and cost more than NASA said it would. Haven’t the discoveries Hubble made possible been worth it?
“A few years after launch most people won’t even remember all this,” Plait said via email. “Hubble had very similar problems, including a devastating equipment flaw that held up most science for two years (as I well know; I was using Hubble then) and which was a massive PR disaster for NASA. Within a few years after the problem was fixed, people had more or less forgotten, and it’s now an icon of astronomy and NASA. The same could well be true for [Webb].”
And in a mere half-decade, just think of the wonders we’ll see.