Webb Telescope Reaches Operational Orbit

JWST trajectory.
Credit: NASA

CAPE CANAVERAL—A month after launching aboard an Arianespace Ariane 5 rocket, the James Webb Space Telescope (JWST) on Jan. 24 reached its operational orbit about 940,000 mi. from Earth.

At 2 p.m. EST, JWST fired its onboard thrusters for a third and final course correction maneuver since its launch on Dec. 25. The 297-sec. burn accelerated JWST’s speed by 3.6 mph, allowing it to slip into a looping, 180-day orbit around the second Earth-Sun Lagrange point (L2). 

Lagrange points are locations where the gravitational forces of two bodies, such as the Earth and the Sun, are at equilibrium for a small-mass spacecraft to maintain orbit with minimal fuel expenditure, prolonging its operational life. JWST joins the European Space Agency’s (ESA) star-mapping Gaia astrometry observatory and the Russian-German Spektr-RG X-ray observatory in orbit at L2.

Along the way to L2,  the Webb telescope, which had been folded up to fit inside the Ariane 5 payload fairing for launch, deployed a solar array, communications antenna, five-layered sunshield, primary and secondary mirrors and other components. The reconfiguration set the stage for studies of the early universe beyond the imaging power of the still-operational Hubble Space Telescope.

With the tennis court-sized sunshield deployed, JWST mirrors and science instruments began cooling to reach to intended operational temperatures of nearly -400F. Once the telescope’s Near Infrared Camera reaches about -280F in about a week, the painstaking process of aligning the primary mirror’s 18 hexagonal segments will begin. The work, which will take about three months, will position the segments so they operate as a single, 21-ft.-dia. mirror—the largest ever flown on a space telescope. Science operations are expected to begin in late June.

Irene Klotz

Irene Klotz is Senior Space Editor for Aviation Week, based in Cape Canaveral. Before joining Aviation Week in 2017, Irene spent 25 years as a wire service reporter covering human and robotic spaceflight, commercial space, astronomy, science and technology for Reuters and United Press International.