In 1991, NASA launched the Earth Science Enterprise (ESE), a comprehensive program to study Earth System Science: how the Earth's systems of air, land, water, and life interact with each other. The ESE program uses a series of polar-orbiting and low inclination satellites to study long-term global observations of the Earth's land surface, oceans, biosphere, atmosphere, and solid earth. Launched into orbit on February 24, 2000 and formerly called EOS AM-1, the Terra spacecraft is "the flagship of NASA's Earth Observing System (EOS)," a critical component of ESE. The Terra Website offers background information on NASA's Earth Science Enterprise program, descriptions of the technology used to measure Earth System variables, and a host of resources including data and publications.