N ASA officials, scrambling to head off a looming budget crisis on the James Webb Space Telescope, are considering easing up on requirements for a number of program elements including schedule, test procedures and the polishing specifications of the observatory’s main mirror.
The idea is to contain a $1.1 billion cost overrun without compromising the program’s scientific objectives. NASA officials are hopeful, but concede that they are not sure yet whether the proposed strategy would offset the entire overrun on the flagship-class astronomy mission, which was supposed to cost $3.5 billion.
“Perfect would be to get right back into the box, but we’ll have to see what they can do,” said astronomer Eric Smith, the Webb program scientist at NASA headquarters in Washington, referring to the Webb program management staff at NASA’s Goddard Space Flight Center in Greenbelt, Md. The program managers will receive a revised set of Webb science priorities from a new Science Assessment Team for the program that began its work in June.
For now, NASA has dropped 2011 as the official launch date for the telescope. “We’ve given the program freedom on the launch date. We want them to come back with a reduced cost and optimized spending profile,” Smith said.
The James Webb Space Telescope is billed as the successor to the Hubble Space Telescope, arguably NASA’s most productive scientific endeavor to date. But whereas Hubble looks at the cosmos almost exclusively in visible wavelengths of light, Webb will focus on infrared wavelengths to give humans their first glimpse of the universe not long after the Big Bang.
Astronomers believe the first light given off by the universe now reaches Earth in the infrared due to the expansion of the universe. Webb will collect light at those faint infrared wavelengths with a 6.5-meter-wide mirror that will unfold in space at a vantage point 1.5 million kilometers away from Earth, whose heat otherwise might overwhelm the signals. The mirror will reflect the infrared signals to a module of science instruments.
Smith said that when he learned of the budget crisis in March, he immediately asked program officials to examine the impact of dramatically scaling back the size of Webb’s primary mirror. “That was found to: one, not accomplish the science; and two, not save as much money as we hoped,” Smith said.
The reason reducing the mirror’s size won’t save much money is that its 18 raw segments, or blanks, were too far along in production. Contractor Brush Wellman of Elmore, Ohio, finished forming the unpolished blanks earlier in August.
“We knew from that quick study that just chucking stuff overboard wasn’t the right answer,” Smith said.
NASA officials now are focusing on easing requirements rather than dropping science instruments or mirror segments. Even so, Smith said he could not rule out that the Science Assessment Team might recommend a different approach when it reports to NASA at the end of August.
“I’m waiting just like you to see what they come back with,” Smith said.
NASA and its James Webb Space Telescope prime contractor, Northrop Grumman Space Technology of Redondo Beach, Calif., like the idea of easing the polishing fidelity requirement for the telescope’s mirror segments.
The existing requirement “would be like taking the 14,000-foot (4,27 0-meter) Rocky Mountains and smoothing and grinding them down to the point that they were the height of a baseball — 3 inches (7.6 centimeters) or so,” said Martin Mohan, the Webb program manager at Northrop Grumman.
“There are certain wavelength bands where a small change in how perfectly we polish these mirrors could allow us to produce them with much less risk but not affect in a significant way the amount of distortion that would be caused,” Mohan said.
Changes in the “overall scale of science would probably be very, very hard to notice,” Mohan added. Meeting the existing requirement might require two to three costly trips between the polishing company, Tinsley Laboratory of Richmond , Calif., and the NASA test facility at Marshall Space Flight Center in Huntsville, Ala., he said.
Northrop Grumman also has suggested that NASA scrap a plan to build a super-cooled tower at the agency’s Johnson Space Center in Houston to test the fully assembled mirror. Current plans call for suspending the entire structure 20 meters above the ground in the tower while light is bounced off the mirror to test its accuracy.
As an alternative, Northrop Grumman proposes placing the mirror on the ground in an existing facility. The mirror would be pointed up for the accuracy testing in what company officials call the “cup up” approach.
“We’re doing the same optical test so there’s no loss in the fidelity,” Mohan said.
Smith said the idea shows promise, but cautioned that the jury is still out. “The project is investigating the implications for this method of testing including cleaning of the mirrors to remove contamination, science impacts of increased contamination levels, etc. We don’t have any conclusions or decisions yet,” he said by e-mail.
NASA officials are considering simplifying other Webb testing procedures, while being mindful of the mirror flaw that nearly doomed the Hubble telescope. “That’s been a big focus of the examination: H ow can we still achieve the science requirement through simpler test procedures? ” Smith said.
The Webb program’s funding crisis surfaced in March during an exchange of correspondence between NASA and Northrop Grumman officials . The company advised NASA that it would need an additional $270 million to make a series of changes to the program requested by the agency.
Those changes included adjustments to the telescope’s instrument module and ground test equipment, Mohan said. NASA also advised Northrop to plan to launch Webb on a European Ariane 5 rocket rather than a U.S. Evolved Expendable Launch Vehicle.
In the case of Webb, “changing one thing tends to ripple more than it does on other programs,” Mohan said.
Meanwhile, officials at NASA headquarters decided to increase the contingency funds Webb managers would have to set aside for unexpected complications.
“When you add together all those components — cost increases from Northrop and its subcontractor, cost increases at Goddard, a delay in the program associated with launch and increases for contingency — that’s when you get to a billion dollars,” Smith said.