Operating the GONG worldwide network

At the instigation of the international scientific community, the US National Solar Observatory (NSO) began to develop the six-site, semi-autonomously operating, helioseismology Global Oscillation Network Group (GONG) in 1984 and the network was officially established in 1995 when the sixth, and last, station was completed. Funded by the US National Science Foundation and enjoying in-kind support from numerous institutions, the project has become a notable international collaboration. The network provides essentially continuous, extremely sensitive observations of the velocity, intensity, and magnetic field of the Sun's surface every minute. Quick-look data are available in near-real-time for science and for diagnostics (http://gong.nso.edu), and the full data set is shipped to project headquarters weekly where the processed data and science-grade analyses are made available to the international community. As originally proposed, GONG was to have a three-year observing run. Over a number of years of operation however, both GONG and its space-borne sister the ESA/NASA SOHO MDI instrument clearly demonstrated the reality of internal solar-cycle structural changes, and in addition, local helioseismology programs were successfully developed. In 2003, NSO made a decision to add GONG to its Flagship facilities and extended the duration of the observing run indefinitely.