The James Webb Space Telescope is the scientific successor to NASA's Hubble Space Telescope and will be the most powerful space telescope ever built. This time-lapse video shows the assembly of the JWST's primary mirror, which was completed February 3. JWST will study many phases in the history of our universe. Itâs targeted to launch in 2018. Webb is an international project led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.