Estimation of ionospheric gradients and vertical total electron content using dual-frequency NAVIC measurements

Abstract

Indian Space Research Organization is being developing a regional satellite radio navigation system known as Navigation with Indian Constellation (NAVIC) satellite system to cater positioning, navigation and timing application. NAVIC has the capability to transmit dual frequency measurements on L5 and S band signals. Ionospheric gradients are one of the pre-dominant error sources with huge impact at the time of geomagnetic disturbed ionospheric conditions in low-latitude region. The large ionospheric gradients can degrade the positional accuracy of NAVIC system. In this paper, ionospheric temporal gradient analysis is carried out in east, west, north and south directions using a Weighted Least Squares (WLS) algorithm for NAVIC L5 signals. The ionospheric gradient algorithm is tested with NAVIC receiver data located at Koneru Lakshmaiah Education Foundation (KLEF) University campus, Guntur, India (16.42∘ N, 80.62∘ E) during geomagnetic storm time conditions (27th–29th May 2017). The results confirmed the increments in VTEC along with longitudinal (E-W) and latitudinal (N-S) gradient magnitudes accordingly with geomagnetic storm effects. The WLS based VTEC model is able to detect E and W ionospheric gradients during the transition period from main phase to recovery phase of the geo-magnetic storm.