Evolution to modernized GNSS ionoshperic scintillation and TEC monitoring

Abstract

Abstract-The ionosphere, if not modeled sufficiently well, is the largest contributor of error in single frequency GNSS receivers. Modeling ionospheric effects is a major concern for a number of GNSS applications. Ionospheric disturbances induce rapid fluctuations in the phase and the amplitude of received GNSS signals. These rapid fluctuations or scintillation potentially introduce cycle slips, degrade range measurements, and if severe enough lead to loss of lock in phase and code. GNSS signals, although vulnerable, themselves provide an excellent way to measure the ionospheric effect continuously worldwide. Until now, ionospheric monitoring was performed using receivers such as the GSV4004B receiver, which was largely based on GPS only dual frequency receivers. Semi-codeless tracking of the GPS L2 signal greatly limited the accuracy, robustness and utility of the ionospheric TEC measurements and was useless for scintillation measurements on L2. The GPS modernization program, the restored GLONASS, and the upcoming GNSS constellations (Galileo and Compass) bring forth huge benefits for ionospheric monitoring. This paper introduces the NovAtel's next generation GNSS ionospheric scintillation and TEC monitor, the GPStation-6. By incorporating the proven GSV4004B receiver design with the ability to track multi-constellation, multi-frequency, GNSS measurements, the new receiver engine provides robust and less noisy ionospheric measurements.

Scintillations of the GPS, GLONASS, and Galileo signals at equatorial latitude

“…Up to now, almost all studies of GNSS scintillations focused exclusively on the GPS L1 frequency Béniguel et al (2009), SBAS Ionospheric Working Group (2010), Sreeja et al (2011), Adewale et al (2012), Paznukhov et al (2012) with few authors considering GPS L2 and L5 Conker et al (2003), Carrano et al (2012), Shanmugam et al (2012) and GLONASS L1, L2 Sreeja et al (2012). To broaden this scope, we present results that compare the influence of scintillations on the new signals to GPS L1.…”

GNSS ionospheric scintillation and TEC monitoring using GPStation-6

“…Nearly 350 GSV4004X GISTM receivers were sold to scientific customers worldwide and are widely used in ionospheric monitoring networks and space weather applications. In 2011, it was discontinued due to a new era in GNSS signal modernization [7].…”

“…There is an offset of about 3.5 TECU as the wideband P(Y) signal is delayed more than the narrower band L2C signal. Interestingly the combination of signal power differences offset by different multipath effects resulting in nearly equal noise performance for both [7].…”

“…Therefore, the distance or range measurement as implied by the integrated carrier phase is short, but that of pseudorange is long. Ionospheric phase and group delay corrections can be obtained by multiplying the TEC with a proportionality constant, which is a function of frequency [7].…”

“…A phase scintillation index of greater than 1 degree is associated with strong scintillation. Both amplitude and phase scintillation measurements should be detrended to extract the contribution from scintillation alone, while attempting to reject the effects of signal dynamics and multipath [7].…”