A Tribute to Paul Kintner

During the most recent solar maximum extending roughly from 1999-2003 GNSS was dominated by GPS and services utilizing GPS. GPS had been declared operational in 1995 during the solar minimum and selective availability was eliminated in 2000. So during the past solar maximum the first efforts at creating precise, a few meters, positional and navigation services emerged both as public and private differential systems and as augmentation systems such as WAAS. Also during this period civilian dual frequency TEC GPS receivers were also deployed in large arrays and their data were made publically available on a voluntary basis. From the space weather viewpoint two results occurred. First the arrays to TEC receivers revealed immense ionospheric storms at mid-latitudes with sharp gradients in TEC. Second the differential and augmentation systems discovered that their architectures were inadequate to provide consistent corrections in regions of ionospheric gradients. These two trends collided on October 29 and October 30 when an extended magnetic storm made the WAAS vertical navigation service unavailable for a period exceeding 26 hours. In approaching the next solar maximum at roughly 2013 the new trends are surprisingly similar. First the deployed GNSS technology is overwhelmingly based on legacy GPS signals. GLONASS is near operational but few receivers use GLONASS signals. New GPS satellites with new signals and more robust codes are being launched but the overwhelming majority of operational GPS receivers will use the legacy GPS signals during the next solar maximum. Galileo is currently predicted to be operational by 2014 but given the past history receiver manufactures are reluctant to invest until the system is proven. Hence Galileo capable receivers will not be widely available and deployed until the next solar minimum. On the other hand providers of PNT services are not sitting still and are now providing very precise services with a few centimeters accuracy. This includes the precision use of heavy equipment in mining and construction, precision agriculture, positioning of off-shore oil platforms, and surveying. These services have dramatically increased over the past solar minimum along with the assumption that the services will be truly uninterrupted and continuous. Providers of these services should be aware of three potential space weather impacts, density gradients as before, scintillation and especially phase scintillation which has only recently been resolved, and solar radio bursts about which we know little. This talk will discuss how to recognize these space weather effects, how to prepare for them, and their potential impact.