An Ionospheric Scintillation Monitor (ISM) is a single- or dual-frequency GPS receiver specifically designed to monitor ionospheric scintillation levels in real time. The ISM has wide-bandwidth tracking loops to maintain lock longer during intervals of strong ionospheric scintillation, and samples at a rate of 50 Hz to calculate the scintillation statistics S4 and Prms. The wide-bandwidth tracking improves tracking through strong scintillation however loss of lock on single or multiple satellites can still occur during extreme events, requiring re-acquisition of the GPS signal(s).

SWS Radio and Space Services uses GPS Silicon Valley's GPS Ionospheric Scintillation and TEC Monitor (GISTM) system Model GSV4004B to monitor Ionospheric Scintillation in real time. The GSV4004B consists of an L1/L2 GPS Antenna, a dual-frequency GPS receiver (NovAtel's Euro-3M with modified firmware), and a low phase noise oven-controlled crystal oscillator (OCXO), housed in NovAtel's EuroPak-3M enclosure. The OCXO is required for monitoring phase scintillation.

The primary purpose of the ISM system is to collect ionospheric scintillation statistics (S4 and Prms) for all visible GPS satellites (up to eleven satellites) and store these (ISMR) binary data logs on the receiver controller hard disk for post processing. The ISM control software can be programmed to collect the ISMR data logs that are generated every 1 minute. Alternatively, raw phase and amplitude data at 0.02 second temporal resolution (50 Hz) and code/carrier divergence at 1 s (1 Hz) can be recorded from the ISM. These data can be used to reconstruct the statistical scintillation indices, such as S4 recorded in the ISMR data log, from raw data. This allows the user to modify the parameters used in the derivation of scintillation indices, such as de-trending and filter cut-off parameters.

The Willis Island Ionospheric Scintillation Monitor station near Willis Island, Queensland, Australia, has a digital Ionospheric Scintillation Monitor GPS since December 2010.