The James Webb Space Telescope builds on the success of NASA’s “Great Observatories,” a series of orbiting telescopes that NASA began building in the 1980s as a way of seeing the cosmos at all wavelength bands. Each of these large, highly sophisticated space telescopes looks at a specific window of the electromagnetic spectrum — from gamma rays to infrared. Webb is part of NASA's Origins program, which seeks to answer fundamental questions about the universe.

Chandra X-Ray Telescope
The Chandra X-Ray Observatory — formerly known as the Advanced X-Ray Astrophysics Facility (AXAF) — was deployed on July 23, 1999. Chandra is looking at some of the most energetic objects in the universe.

Hubble Space Telescope
Named after American astronomer Edwin P. Hubble, the Hubble Space Telescope was launched in 1990 and has since found never-before-seen stars and galaxies — exceeding astronomers’ expectations. With its suite of onboard instruments, Hubble is capable of seeing objects emitting ultraviolet, visible, and infrared radiation.

Spitzer Space Telescope
Launched in August 2003, this infrared-detecting telescope is answering fundamental questions about the birth and evolution of the universe. It can study fetal stars, detect other solar systems, and examine ancient, distant galaxies toward the edge of the universe. The primary Spitzer mission will continue until 2009, when the cryogens that cool the telescope -- essential for instruments that look for infrared radiation -- will be expended.

Compton Gamma Ray Observatory
The second of NASA's Great Observatories looked at astronomical objects that emit gamma rays, the most energetic form of light. Compton, whose mission ended in June 2000 in a fiery reentry into Earth's atmosphere, was at 17 tons the heaviest astrophysical payload flown to date. Over 700 scientists used the satellite and its instruments to survey the surrounding universe.

Space Telescope Wavelengths

Telescopes view the sky in different wavelengths. That means they look at different types of electromagnetic radiation, "seeing" the universe in types of light the human eye cannot detect. Webb's specialty is the infrared portion of the spectrum.