NASA’s Spitzer Space Telescope Program was the fourth and final Great Observatory, launched on 25 August 2003 to study the universe in infrared and decommissioned on 30 January 2020 after more than 16 years of operations. The mission directly detected exoplanet light, mapped exoplanet weather, discovered a new ring around Saturn, and helped reveal the seven Earth-sized planets of the TRAPPIST-1 system.