Webb Telescope Reaches Operational Orbit
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.