The $10 billion James Webb Space Telescope has arrived at its deep-space destination, but it will be some time before the telescope begins its science job.
Webb entered orbit around the Earth-sun Lagrange Point 2, a gravitationally stable location in space 930,000 miles (1.5 million kilometers) from our planet, on Monday (Jan. 24). The highly awaited observatory's arrival followed a month-long voyage, but there are still a lot of boxes to check before Webb gets down to business.
"We expect the first science images from JWST to come back in about five months," Amber Straughn, the deputy project scientist for Webb science communications, said during a webcast Webb event on Monday.
"So, be getting excited, getting ready for those to come back later on this summer," added Straughn, who's based at NASA's Goddard Space Flight Center in Greenbelt, Maryland.
Over the next five months, the Webb team will focus on two significant projects. The first step will be to precisely align the 18 hexagonal segments that make up Webb's 21.3-foot-wide (6.5-meter) primary mirror, which will take around three months.
For Webb to work well, the resulting light-collecting surface must be practically flawless. The biggest bump on the finished primary mirror, if it were the size of the continental United States, would be only an inch or two high, according to Straughn.
After Webb's optics and related sensors have cooled enough to allow such work, mirror-segment alignment is expected to begin next week. (Because Webb is supposed to survey the cosmos in infrared light — wavelengths we perceive as heat — everything aboard it is built to operate at extremely low temperatures, and even the tiniest infrared emissions from the scope might drown out the faint heat signals it's looking for.)
The Webb team will focus each of the 18 primary mirror segments on a bright, distant star to facilitate mirror alignment. And they've already decided on this target: HD 84406, a sunlike star in the constellation Ursa Major (The Great Bear).
"It's just near the bowl of the Big Dipper," Lee Feinberg, the Webb optical telescope element manager at NASA Goddard, said in a different webcast event on Monday. "You can't quite see it with your naked eye, but I'm told you can see it with binoculars."
The Webb crew will align the primary mirror with the 2.4-foot-wide (0.74-meter) secondary mirror, which is named for the second surface photons will encounter on their route into the observatory's four science equipment. According to team members, the milestone will mark the end of the major mirror development.
Webb's instruments, on the other hand, will need to be checked out and calibrated, which is a time-consuming process. By late June or early July, the team expects to have completed everything and be ready to begin using the telescope's super-sharp eyes in earnest.
At that point, the observatory will be up and functioning. According to Straughn, the first year of science observations has already been planned.
"We will be looking at things in the universe ranging from objects within our own solar system, all the way out to searching for the very first galaxies to be born after the Big Bang and everything in time and space in between," she said. "It's going to be awesome."
