The Webb Space Telescope completed its complex mirror deployment this week, and the observatory is getting tantalizingly close to completing its journey to L2, where it will orbit the Sun a million miles away from Earth.
Webb is travelling to the second Lagrange point, a position in space that will allow the telescope to use minimal fuel to stay in position. From L2, the telescope will observe the early universe and exoplanets in the infrared and near-infrared wavelengths. The telescope is expected to overhaul our understanding of the universe’s birth and evolution, as it will peer farther back in time than the Hubble Space Telescope, Webb’s predecessor, which was launched in 1990.
Webb rocketed to space on December 25 from French Guiana and has since traversed 1,384,036 km. During this journey, the telescope been steadily unfurling; to make it practical to launch, engineers had to fold it up like a caterpillar in a chrysalis. In careful steps, it has unfurled its sunshield and deployed its mirrors, with the latter step fully completed this week.
Webb has 18 primary mirror segments (the primary mirror is the big honeycomb structure that stands perpendicular to the sunshield) and a secondary mirror; the mirror segments are adjustable and had to be individually shifted from their launch configuration to their positions for scientific observations. NASA Administrator Bill Nelson confirmed the completed mirror deployment on Wednesday.
Tiny incremental adjustments to the mirror positions will happen over the next several months to get everything into the right optical alignments for observation, according to the Webb deployment schedule. But now that deployment is done, only one major step remains: the fuel burn to insert the telescope at L2. This is the final fuel burn by Webb during its deployment schedule, though future burns will happen occasionally to correct the telescope’s orbit.
The telescope should be orbiting L2 by January 23, after which it will have five months of commissioning to prepare it for scientific observations. The telescope’s million-mile journey is just the preamble to a brilliant scientific career, which could last some 20 years.