From Research/Campaign Mode to Long-Term Air Quality Monitoring: The Evolution of the Pandonia Global Network (PGN)

The Pandora Spectrometer System for the ground-based, sun/sky/lunar passive remote sensing of trace gases in the UV/Vis spectral wavelengths was first developed in 2005. Since that time the Pandora spectrometer system has continued to evolve with the participation in a series of field campaigns such as DISCOVER-AQ, CINDI 1&2, and the 2018 OWLETS and LISTOS campaigns. As the effort has evolved, NASA and ESA are collaborating to coordinate an expanding global network of standardized, calibrated Pandora instruments focused on air quality and atmospheric composition. The Pandonia Global Network (PGN) will endeavor to ensure systematic processing and dissemination of the data to the greater global community in support of in-situ and remotely sensed air quality monitoring. A major joint objective is to support the validation and verification of more than a dozen LEO and GEO satellites, most notably Sentinel 5P, TEMPO, GEMS and Sentinel 4. PGN participants are primarily comprised of governmental and academic researchers and technicians. The launch of the PGN this year represents a programmatic shift by NASA and ESA away from primarily operating and supporting in research and field campaign mode to establishing long-term fixed locations that are focused on providing long-term quality observations of total column and vertically resolved concentrations of a range of trace gases. The major trace gases observed by the Pandora systems across the range of 280 - 530 nm include: O₃, NO₂, HCHO, SO₂ and BrO. A quick overview of the roles and responsibilities of the NASA and ESA designated teams is given along with insight into the standardized PGN calibration process. Information concerning the real-time data processing of Pandora spectrometer system observations as well as their accuracy and precision of the observations of those gases are presented. Furthermore, guiding principles, expectations of participation in the PGN, and the current geographic distribution of instruments will be discussed. The evolution of this network has been modeled in many ways in the spirit of other ground-based atmospheric composition networks, most notably AERONET, TOLNET, and MPLNET.