NASA’s ground-based remotely sensed measurements have played a significant role in developing Earth System Science worldwide.  Particularly notable is the AERosol RObotic NETwork (AERONET) for its unique measurements and retrievals, continuous and long-term records, and pioneering public domain database.   AERONET is a federated network of sun and sky scanning spectral radiometers designed to automatically measure spectral total column aerosol optical depth, as well as radiometric and microphysical properties. The program provides a long-term, continuous and readily accessible public domain database for aerosol research and characterization, validation of satellite retrievals, and synergism with other databases. The network imposes standardization of instruments, calibration, processing and distribution.  Because the network is a federation of national and international partners, AERONET has grown over the last 15 years to be globally distributed at over 400 sites in diverse aerosol regimes ranging from maritime, desert, urban/industrial and biomass burning aerosols.  The project has imposed standards on sun photometry that allows for quantitative and near real-time assessment and intercomparison of widely disparate regions on the Earth thus AERONET data has provided the means to improve the algorithms and models used to retrieve aerosol properties from satellites and global transport models.  Analysis of AERONET data provides aerosol climatologies, trend analysis over 15 years and fundamental properties of aerosol types and mixtures.  This colloquium will include a brief historical perspective of sun photometry, address the development and scientific accomplishments of AERONET and will conclude with a proposed new regional field campaign that will call for volunteers from the audience.   The AERONET team will be acknowledged.