Which NASA observatory program includes Hubble, Compton, Chandra, and Spitzer?

Hubble, Compton, Chandra, and Spitzer were NASA’s Great Observatories.

The Great Observatories program consisted of four major space telescopes designed to study different regions of the electromagnetic spectrum. Hubble observed mainly visible and ultraviolet light, Compton studied gamma rays, Chandra examined X-rays, and Spitzer observed infrared radiation. Together, they gave astronomers a broad, multi-wavelength view of the universe.

The program’s underlying idea was that celestial objects reveal different physical processes at different wavelengths. For example, visible light can show stars and galaxies, infrared can penetrate dusty regions and trace cool objects, X-rays can reveal hot gas and accreting black holes, and gamma rays expose some of the universe’s most energetic events.

Hubble launched in 1990, Compton in 1991, Chandra in 1999, and Spitzer in 2003. Compton was de-orbited in 2000, while Spitzer’s mission ended in 2020. Hubble and Chandra continued operating much longer. The program is sometimes confused with NASA’s Explorer, Discovery, or New Frontiers programs, which are separate mission classes rather than this coordinated set of observatories.