Fast facts about the James Webb Space Telescope

Primary Mirror Stats

Webb Telescope's Mirror Size and Material
The size of Webb's primary mirror was determined by scientists and engineers in order for the telescope to observe distant galaxies at over 13 billion light-years away. The team also decided to make the mirror segments from beryllium, which is both strong and light. CREDIT: NASA and E. Wheatley (STScI). GET THE FULL IMAGE IN RESOURCE GALLERY >

Mirror Type:

Segmented parabolic reflector


21.6 feet (6.5 meters) at its widest point


269 square feet (25 m²)


1,554 lbs (705 kilograms)

Focal Length:

414.4 feet (131.4 meters)

Optical Resolution:

0.07 arc-seconds, diffraction-limited at 2-micrometer wavelengths (0.0317 arc-second pixels)


Beryllium, with a thin coating of gold

Number of Segments:

18 segments

Observatory Stats

Operating Temperature:

-387.7 degrees Fahrenheit (40 kelvin; -233.2 degrees Celsius)

Observatory Mass:

About 14,000 pounds (6,330 kilograms)

Sunshield Size:

70 by 48 feet (21.2 by 14.6 meters)

Planned Launch:


JWST and the Ariane 5 rocket
Left: JWST stowed inside the Ariane 5 rocket. ILLUSTRATION CREDIT: Courtesy of Right: Ariane 5 Launch Vehicle. PHOTO CREDIT: ESA-CNES-Arianespace/Optique Vidéo du CSG-OV.

Launch Vehicle:

Ariane 5 rocket, provided by the European Space Agency

Launch Site:

The Centre Spatial Guyanais (CSG) in Kourou, French Guiana


Orbiting the Sun 940,000 miles (1.5 million kilometers) from Earth at the Second Lagrange Point (L2)

Orbit Shape:

As seen from Earth at midnight, the Webb orbit completes a large loop of 1,000,000 kilometers in diameter twice a year.

Transit Time to Orbit:

About 1 month

Science Mission Lifetime:

5 years, with a goal of 10 years

Solar Array Power:

2,000 watts

Maximum Data Rate (Deep Space Network):

28 megabits per second (Mbps)

Cost at Launch:

$8 billion, plus ESA and Canadian Space Agency (CSA) contributions

Webb Telescope Post-Launch Deployment Timeline
Nearly a month after launch, a trajectory correction will be initiated to place the JWST into a halo orbit at L2. CREDIT: NASA and M. Clampin, GSFC. GET THE FULL IMAGE IN RESOURCE GALLERY >

Instrument Stats

Webb's Science Instruments
Positioned behind the primary mirror, Webb's four science instruments will receive the light collected by the telescope and use a variety of tools—cameras, spectrographs, and coronagraphs—designed to maximize the scientific knowledge gleaned from every observation. CREDIT: NASA and STScI. GET THE FULL IMAGE IN RESOURCE GALLERY >

Wavelength Coverage:

0.6–28.5 micrometers


  • Near-Infrared Camera (NIRCam) (0.6–5 micrometers)
  • Near-Infrared Spectrograph (NIRSpec) (0.7–5 micrometers)
  • Mid-Infrared Instrument (MIRI) (5–28.5 micrometers)
  • Near-Infrared Imager and Slitless Spectrograph (NIRISS) (0.6–5 micrometers)

Last Updated: May 31, 2018

Keywords: Webb Mission

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