Development and use of a GPS ionospheric scintillation monitor

Besides their intended use in radionavigation, global positioning system (GPS) satellite signals provide convenient radio beacons for ionospheric studies. Among other propagation phenomena, the ionosphere affects GPS signal propagation through amplitude scintillations that develop after radio waves propagate through ionospheric electron density irregularities. This paper outlines the design, testing, and operation of a specialized GPS receiver to monitor L-band amplitude scintillations: the Cornell scintillation monitor. The Cornell scintillation monitor consists of a commercial GPS receiver development kit with its software modified to log signal strength from up to 12 channels at a high data rate (50 samples/s). Other features of the receiver include the optional assignment of a channel to monitor the receiver noise level in the absence of signal tracking and the means to synchronize measurements between nearby independent receivers to perform drift measurements and correlation studies. The Cornell scintillation monitor provides characterization of the operational L-band scintillation environment and additionally permits study of the multipath environment of a static antenna. GPS scintillation monitors can provide information about the state of ionospheric irregularities for pure research purposes as well. Here their strength lies in the fact that they are inexpensive and compact and therefore can be readily proliferated. Even a single scintillation monitor can supplement radar spatial coverage of irregularities in a limited way because it monitors several satellite lines of sight simultaneously. This article introduces some of the potential of the scintillation monitor for research, primarily through examples associated with field testing the instrument.