Nasa has begun the months-long, tedious process of bringing its recently launched James Webb space telescope into focus, a work that should be completed by early summer in time for the revolutionary eye in the sky to begin looking into the universe.
Engineers at Nasa’s Goddard space flight center in Greenbelt, Maryland, started by sending signals to small motors known as actuators, which steadily move and fine-tune the telescope’s main mirror.
The primary mirror is 6.5 metres (21ft 4in) in diameter and is made up of 18 hexagonal segments of gold-plated beryllium metal — a significantly bigger light-collecting surface than Webb’s predecessor, the 30-year-old Hubble observatory.
Following Webb’s launch on Christmas Day, the 18 segments, which had been folded together to fit into the cargo bay of the rocket that took the telescope to orbit, were unfolded with the rest of the telescope’s structural components during a two-week period.
Before they can be aligned to create a single, unbroken, light-collecting surface, those segments must be removed from the fasteners that held them in place for the launch and pushed forward by approximately a millimetre from their original configuration — a 10-day procedure.
According to Lee Feinberg, the Webb optical telescope element manager at Goddard, the alignment will take another three months.
According to Feinberg, when the principal mirror segments are aligned to form one giant mirror, each segment is “aligned to one-five-thousandth the thickness of a human hair.”
“All of this necessitated us inventing things that had never been done before,” he said, citing the actuators, which were designed to move gradually at -240C (-400F) in space’s vacuum.
The smaller secondary mirror on the telescope, which directs light captured from the primary lens onto Webb’s camera and other equipment, must also be oriented to work as part of a coherent optical system.
If all goes according to plan, the telescope should be ready to take its first science photographs in May, which will be analyzed for another month before being provided to the public, according to Feinberg.
The $9 billion telescope, dubbed “the leading space-science observatory of the next decade” by Nasa, will primarily observe the universe in the infrared wavelength, allowing it to peer through clouds of gas and dust where stars form. Hubble’s primary wavelengths of operation have been optical and ultraviolet.
Webb’s telescope is nearly 100 times more powerful than Hubble’s, allowing it to study things at greater distances and consequently further back in time than Hubble or any previous telescope.
According to astronomers, this will provide a hitherto unseen image of the cosmos, dating from only 100 million years after the Big Bang, the hypothesized spark that started in motion the expansion of the visible universe 13.8 billion years ago.
Nasa is leading an international effort with the European and Canadian space agencies to build the telescope.