Webb Key Facts

The James Webb Space Telescope (sometimes called JWST or Webb) is an orbiting infrared observatory that will complement and extend the discoveries of the James Webb Space Telescope, with longer wavelength coverage and greatly improved sensitivity. The longer wavelengths enable Webb to look much closer to the beginning of time and to hunt for the unobserved formation of the first galaxies, as well as to look inside dust clouds where stars and planetary systems are forming today. KEY FACTS: Proposed Launch Date: December 25, 2021 07:20am EST ( 2021-12-25 12:20 GMT/UTC) Launch Vehicle: Ariane 5 ECA Mission Duration: 5 - 10 years Total payload mass: Approx 6200 kg, including observatory, on-orbit consumables and launch vehicle adaptor. Diameter of primary Mirror: 6.5 m (21.3 ft) approximately Clear aperture of primary Mirror: 25 m2 Primary mirror material: beryllium coated with gold Mass of primary mirror: 705 kg Mass of a single primary mirror segment: 20.1 kg for a single beryllium mirror, 39.48 kg for one entire primary mirror segment assembly (PMSA). Focal length: 131.4 meters Number of primary mirror segments: 18 Optical resolution: ~0.1 arc-seconds Wavelength coverage: 0.6 - 28.5 microns Size of sun shield: 21.197 m x 14.162 m (69.5 ft x 46.5 ft) Temp of sun shield layers: Layer 1: Max temperature 383K = approx 231F Layer 5: Max temperature 221K = approx -80F Min temperature 36K = approx -394F Orbit: 1.5 million km from Earth orbiting the L2 Point Operating Temperature: under 50 K (-370 °F) Gold coating: Thickness of gold coating = 100 x 10-9 meters (1000 angstroms). Surface area = 25 m2. Using these numbers plus the density of gold at room temperature (19.3 g/cm3), the coating is calculated to use 48.25g of gold, about equal to the mass of a golf ball. (A golf ball has a mass of 45.9 grams. Note mass does not equal size!)