The James Webb Space Telescope (JWST), previously known as Next Generation Space Telescope (NGST), is a flagship-class space observatory under construction and scheduled to launch in October 2018. The JWST will offer unprecedented resolution and sensitivity from long-wavelength (orange-red) visible light, through near-infrared to the mid-infrared, and is a successor instrument to the Hubble Space Telescope and the Spitzer Space Telescope. The telescope features a segmented 6.5-meter (21 ft) diameter primary mirror and will be located near the Earth–Sun L₂ point. A large sunshield will keep its mirror and four science instruments below .