Webb’s segmented primary mirror has a diameter of 6.5 meters (21.6 feet). Each of the 18 segments is 1.4 meters (4.5 feet) in diameter. The area of the mirror is 25 square meters (269 square feet) and the mass is 705 kilograms (1,554 pounds).
The sunshield dimensions are 21.2 by 14.2 meters (69.5 by 46.5 feet) and the height of the entire observatory is 8 meters (28 feet).
To accurately and precisely detect faint infrared light from distant objects in the universe, Webb must be shielded from the strong infrared light emanating nearby from the Sun, Earth, and Moon. The sunshield’s five layers block the light from these nearby objects.
Webb is designed to have a minimum five years of science operations, with the goal of having an overall mission lifetime greater than 10 years.
Webb has four scientific instruments, the Near-Infrared Camera (NIRCam), the Near-Infrared Spectrograph (NIRSpec), the Near-Infrared Imager and Slitless Spectrograph (NIRISS), and the Mid-Infrared Instrument (MIRI). Each of these instruments uses infrared detectors to capture light from distant astronomical sources.
The Webb telescope is powered by an on-board solar array. It also has a propulsion system to maintain the observatory’s orbit and attitude. The solar array provides 2,000 watts of electrical power for the life of the mission, and there is enough propellant onboard for at least 10 years of science operations.
Webb can downlink at least 57.2 gigabytes of recorded science data each day, with a maximum data rate of 28 megabits per second.
The sunshield layers are built with ripstops included, so if something pierced a layer, it couldn't rip very far, allowing the layer to maintain structural integrity.
The primary mirror segments and secondary mirror are moved by six actuators that are attached to the backs of the mirrors. The primary segments have an additional actuator at the center of the mirror to adjust their curvature. Those seven spots are adjustable to align the 18 segments of the primary mirror to each other, and adjust the primary and secondary mirrors to the fixed tertiary mirror and the instruments.
Over the course of six months, as Webb orbits the Sun with the Earth, it has the ability to observe any point in the sky. Webb’s field of regard is limited to a 50-degree swath of the celestial sphere.