Yury Yasyukevich

Investigation of SBAS L1/L5 Signals and Their Application to the Ionospheric TEC Studies

With the development of satellite-based augmentation systems (SBAS), the dual-frequency L1/L5 observations from a number of geostationary satellites are now available. It provides the possibility of retrieving ionospheric total electron content (TEC) from these observations using the same approach as for dual-frequency GPS/GLONASS observations. In this letter, we study L1/L5 signals of American Wide Area Augmentation System (WAAS) and Indian GPS and geo-augmented navigation system (GAGAN) geostationary satellites observed with geodetic Global Navigation Satellite System (GNSS) receivers located at equatorial and midlatitudes and estimate corresponding geostationary TEC and errors of such estimations. One-hundred-second TEC RMS was found to reach up to 1.5 TEC unit (TECU) with typical values of 0.25-0.5 TECU, which is several times greater than for GPS/GLONASS observations. TEC RMS also manifests UT dynamics, which is specific for the satellite and not relevant to the signal paths. SBAS TEC was found to be in good agreement with the data of nearest ionosondes. We also conduct the wavelet analysis of geostationary TEC, providing typical periods of observed variations at different timescales and discuss the capabilities of SBAS TEC observations in connection with ionospheric effects of X1.7 solar flare on October 25, 2013.

Ionospheric variations during typhoons of autumn 2016

We study variations of total electronic content (TEC) during typhoons, observed in the August-September 2016 in the North-West Pacific Ocean. The TEC data were obtained from phase dual-frequency measurements of GPS/GLONASS ground-based receivers. Using the indexes of ionospheric variability within different period ranges we revealed an increase in the intensity of ionospheric disturbances with periods of internal gravity waves (IGW-variability, from 2 minutes till 4 hours) at the stations located close to the typhoon regions. The most intensive variations are shown to be occurred after passage of the solar terminator and localized near the typhoon boundary. The greatest increase in TEC IGW-variability is recorded during the days of abrupt changes in the cyclones intensity (growth/fall in wind speed).

Ionosphere and magnetosphere disturbance impact on operation slips of Global navigation satellite systems at mid- and high-latitudes

We studied the dynamics of the GLONASS and GPS radio physical signal slips, as well as the slips in determining the total electron content (TEC) at the stations in the mid- and high-latitude regions under different geophysical conditions over 2014 Nov - 2015 Jul. At high latitudes, the pseudo-range P1 measurement slip density is shown to be lower for the GLONASS system, than that for GPS. At mid-latitudes, the TEC slip mean density (N1 TECU/min) under quiet geomagnetic conditions practically does not depend on the Kp and AE index behavior, and does not exceed 12%. At high-latitudes, N1 TECU/min in winter is generally higher, than that in the summer, and may reach 50-60%. The N1 TECU/minvariation at highlatitudes correlates with the geomagnetic index behaviors; however, it depends on Kp and AE essentially differently. Under disturbed conditions, N1 TECU/min increases as AE grows more slowly, that it does under quiet conditions. On the contrary, N1 TECU/min growth as Kp increases under disturbed conditions occurs on a factor of 1,5 faster, than it does under quiet geomagnetic conditions. The N1TECU/min value dependences on the ionospheric disturbance index (Wtec) at mid- and high-latitudes are similar. An increase in the TEC slip density, N1TECU/min in wintertime occurs on a factor of 1,5 faster, than it does in summer. Simultaneously, at high-latitudes, the N1TECU/min growth with the Wtec increase occurs on a factor of 2-2,5 faster, than it does at the mid-latitudes.

Systematic changing and variations of GPS/GLONASS differential code biases

Along with navigation and precise time applications, Global Navigation Satellite Systems (GNSS) are widely used nowadays to remotely sense the ionosphere in equatorial, mid-latitude and arctic regions. While estimating absolute TEC using the code and phase measurements simultaneously, a satellite and receiver dependent systematic error occurs. This error is associated with differential code biases (DCB) - the different, frequency dependent processing times of L1 and L2 signals in RF paths, both for satellites and receivers. Due to these DCBs, TEC, in some cases, can obtain even non-physical negative values. For example, a 1-ns DCB causes a ∼3 TECU error in TEC estimation.

Global distribution of GPS losses of phase lock and total electron content slips during the 2005 May 15 and the 2003 November 20 magnetic storms

Аннотация. На основе данных глобальной сети приемников GPS рассмотрены срывы сопровождения фазы навигационного сигнала GPS во время двух сильных магнитных бурь. Показано, что плотность сбоев на основной частоте L1 увеличивается до 0.25 %, на вспомогательной частоте L2 — до 3 %, в разы превышая фоновый уровень. Число сбоев измерения полного электронного содержания (ПЭС) во время супербури 20 ноября 2003 г. возросло в ~50 раз относительно фонового уровня. Обнаружено, что во время супербурь наибольшее число сбоев сопровождения фазы наблюдается в регионах низких и высоких широт. В то же время область наибольших сбоев измерения ПЭС соответствует границам аврорального овала.