Estimation of Satellite-Based Augmentation System Grid Size at Low Latitudes in the Indian Zone

Paul, Ashik; Chakraborty, Subhadeep; Das, Arijit; Dasgupta, Anjan Kr.; Mitra, S.

doi:10.1002/j.2161-4296.2005.tb01727.x

Cited by 18 publications

(19 citation statements)

References 6 publications

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“…To avoid the multipath effect an elevation cut-off of 20 • is selected. For GPS TEC data an elevation cut-off of 50 • is considered to make the slant to vertical conversion more accurate (Paul et al, 2005). Appropriate satellite and receiver bias corrections are incorporated.…”

Section: Published By Copernicus Publications On Behalf Of the Europementioning

confidence: 99%

Variability of ionospheric scintillation near the equatorial anomaly crest of the Indian zone

Chatterjee¹,

Chakraborty²

2013

Ann. Geophys.

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Multistation observations of ionosphere scintillation at VHF (250 MHz) and GNSS L1 frequency from three locations – (i) Bokkhali (BOK) (geographic 21.6° N, 88.2° E, dip 31.48°, (ii) Raja Peary Mohan College Centre (RPMC) (geographic 22.66° N, 88.4° E, dip 33.5°) and (iii) Krishnath College Centre (KNC), Berhampore (geographic 24.1° N, 88.3° E, dip 35.9°) – at ~ 1° latitudinal separations near the northern crest of the equatorial ionization anomaly (EIA) of the Indian longitude sector are investigated in conjunction with total electron content (TEC) data and available ionosonde data near the magnetic equator to study fine structure in spatial and temporal variability patterns of scintillation occurrences. The observations are carried out in the autumnal equinoctial months of a high solar activity year (2011). In spite of smaller latitudinal/spatial separation among the observing stations, conspicuous differences are reflected in the onset time, duration, fade rate and fade depth of VHF scintillations as well as in spectral features. Scintillations are mostly associated with depletion in TEC around the anomaly crest and occurrence of ESF near the magnetic equator at an earlier time. Not only the strength of EIA, but also the locations of observing stations with respect to the post-sunset resurgence peak of EIA seem to play dominant role in dictating the severity of scintillation activity. A secondary enhancement in diurnal TEC in the post-sunset period seems to accentuate the irregularity activities near the anomaly crest, and a threshold value of the same may fruitfully be utilized for the prediction of scintillation around the locations. An idea regarding latitudinal extent of scintillation is developed by considering observations at L1 frequency from the GPS and GLONASS constellation of satellites. A critical value of h'F near the magnetic equator for the occurrence of simultaneous scintillation at the three centres is suggested. The observations are discussed considering electrodynamical aspect of equatorial irregularities

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Section: Published By Copernicus Publications On Behalf Of the Europementioning

confidence: 99%

Variability of ionospheric scintillation near the equatorial anomaly crest of the Indian zone

Chatterjee¹,

Chakraborty²

2013

Ann. Geophys.

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“…Different models such as IRI, PIM, SLIM and SUPIM are available for evaluation of TEC. But studies (Ezquer et al, 2004;Paul et al, 2005) reveal that no model in general is sufficient to represent TEC variation around the anomaly crest region. Development of a model requires several steps to be followed.…”

Section: Introductionmentioning

confidence: 99%

Electrojet control of ambient ionization near the crest of the equatorial anomaly in the Indian zone

Chakraborty¹,

Hajra²

2009

Ann. Geophys.

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Abstract. A long-term (1978-1990) database of total electron content (TEC) from a location (Calcutta: 22.58 • N, 88.38 • E geographic, dip: 32 • N) near the northern crest of the equatorial ionization anomaly has extensively been studied to characterize the contribution of fountain effect in the maintenance of ambient ionization. The equatorial electrojet (EEJ) data obtained from ground magnetometer recording are used to assess the contribution of equatorial fountain. Analysis made with instantaneous values, day's maximum values and time-integrated values of EEJ strength exhibit more or less similar features. When instantaneous values of EEJ are considered TEC variations exhibit two maxima in correlation, one around 10:00-12:00 IST and the other around 18:00-20:00 IST. The later maximum in correlation coefficient is conspicuously absent when integrated values of EEJ are considered. An impulse-like feature is reflected in the diurnal TEC variation during the time intervals (09:00-10:00 IST) and (18:00-19:00 IST). The statistical analysis reveals greater correspondence with high level of significance between diurnal TEC and EEJ in the descending epoch of solar cycle than in the ascending one. On the seasonal basis, TEC in the summer solstitial months are observed to be more sensitive to the changes in EEJ strength than in the equinoctial and winter solstitial months. Combining the effects of solar flux, season, local time and EEJ an empirical formula for monthly mean diurnal TEC has been developed and validated using observed TEC data. An estimation of the relative contributions of the several terms appearing in the formula reveals much more solar flux contribution (∼50-70%) in the maintenance of ambient ionization around the present location than the EEJ effects (maximum∼20%).

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“…During 1999–2002, combined GPS‐GLONASS receivers were operated at some locations in India where it was reported that availability of GLONASS satellites was limited from equatorial locations (Banerjee et al, ). Studies conducted earlier have reported that the detrimental effects of the sharp latitudinal gradients of ionization occurring in the equatorial region may be limited if sufficient number of satellite links are available at high elevation angles in excess of 60° (Paul et al, ). It has been observed using total electron content (TEC) measured in 2004 along a chain of stations located more or less along 77°E meridian under the Indian Satellite‐Based Augmentation System (SBAS) program GPS‐aided Geo Augmented Navigation (GAGAN) that the median grid scale of latitude and longitude for total electron content variation less than 3 TECU (for an acceptable range error of 50 cm) varied from (0.64°–0.87°) × (0.23°–0.49°) at elevation angles greater than 70° (Paul, Das, et al, ).…”

Section: Introductionmentioning

confidence: 99%

Study of Relative Performance of Different Navigational Satellite Constellations Under Adverse Ionospheric Conditions

2018

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Detrimental effects of satellite signal outages during periods of intense equatorial ionospheric scintillations could be mitigated using multiconstellation satellites if provisions for interoperability of these satellite signals exist. In view of the sharp spatial gradient of ionization occurring in the equatorial region, comparison of satellite signal fluctuations from different constellations should be performed over limited spatial volume. This could be effective for maintaining and improving the performance of satellite‐based communication and navigation without compromising the accuracy and integrity. This paper presents a comparative study of robustness of GPS, GLONASS, and GALILEO satellites over a common ionospheric volume during periods of ionospheric scintillations for the equinoctial months of 2014 and March 2016 from Calcutta (22.58°N 88.38°E geographic; 32°N magnetic dip) and for September 2016 from Siliguri (26.72°N, 88.39°E; 39.49°N magnetic dip), located near the northern crest of equatorial ionization anomaly in the Indian longitude sector. It is found that for all the cases, carrier‐to‐noise ratio fluctuations over limited ionospheric volume from satellites of different constellations are comparable, thereby rendering them interoperable.

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Estimation of Satellite-Based Augmentation System Grid Size at Low Latitudes in the Indian Zone

Cited by 18 publications

References 6 publications

Variability of ionospheric scintillation near the equatorial anomaly crest of the Indian zone

Variability of ionospheric scintillation near the equatorial anomaly crest of the Indian zone

Electrojet control of ambient ionization near the crest of the equatorial anomaly in the Indian zone

Study of Relative Performance of Different Navigational Satellite Constellations Under Adverse Ionospheric Conditions

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