Originally planned as a “one-year mission,” NASA’s Earth Observing-1 (EO-1) satellite celebrated the fifteenth anniversary of its launch on November 21, 2015. EO-1 was originally a technology testbed satel- lite, built quickly and inexpensively. EO-1 is finally heading for the end of its mission, which is pro- jected for October 2016. While the platform and its instruments are operating well, fuel reserves have been exhausted and the satellite has lost its orbital maintenance ability. The impressive milestone of reaching its 15-year anniversary, coupled with the impending end of the mission, provides an excellent time to review EO-1’s origins and goals, its expanded mission, and the utility of the data acquired so far.