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Global Positioning System (GPS) is used for navigational purposes in the missiles during developmental, trials, and war scenario deployment. In this paper, the authors demonstrate typical time and location-dependent visibility problems of the GPS satellites for the elevation angles higher than 60° over a large part of the Indian sub-continent and the adjoining water bodies over the Bay of Bengal and Arabian Sea, which has the potential to adversely affect the missile flights during developmental trials and war scenarios, especially for the low elevation cruise missiles. The Indian regional navigation satellite constellation NavIC can effectively mitigate this visibility problem and ensure system independence from a strategic viewpoint. In this work, the standalone position solution quality of NavIC is evaluated statistically and compared with GPS from the Test Range. Promising results will encourage using the Indian constellation NavIC to ensure better position solution quality and system independence from a defence perspective.

In missile test ranges, complex missions demand precise trajectory generated by radar. Both the radar and Global Navigation Satellite System (GNSS) signals are affected by atmospheric effects, degrading their accuracy and performance. The Indian Regional Navigation Satellite System/Navigation with Indian Constellation (IRNSS/NavIC) transmits signals in the S-band together with the L-band. This paper presents a novel experimental technique to improve the tracking accuracy of S-band radars using the concurrent NavIC S-band signal. The ionospheric delay using the NavIC S-band signal is calculated first, and the results are used to improve the trajectory data of simultaneously operating S-band radars. This is a unique application of the NavIC S-band signals apart from its conventional usage. During a launch mission, for low elevation angles, the ionospheric error is found to be ~130 m while at higher elevation angles the error values are found to be ~1–3 m. The concept is validated using data from a missile test mission. This report on the use of S-band GNSS signals for the correction of S-band radar range data offers a clear advantage of simplicity and accuracy.

Global Navigation Satellite System (GNSS) uses Precise Point Positioning (PPP) technique to find out accurate geolocation information of any point. Generally, costly, geodetic GNSS receivers are used for PPP. This manuscript presents the results of studies on the usability of commercial, compact, cost-effective GNSS modules with commercial antennas for PPP in comparison to commonly used geodetic, costly receivers from India, which is a excellent location for GNSS use. Compact GNSS modules from two manufacturers are used in the study, and the encouraging results show the clear advantage of cost, size, and power requirements of such modules. The modules provide sub-cm horizontal solution accuracy which is very similar to those obtained using geodetic receivers, and around 20 cm accuracy in the vertical coordinate, which is slightly inferior to the results provided by the geodetic reveivers. Results of this novel study would be useful for implementing cost-efficient GNSS PPP in real life, in highly demanding geodetic applications including CORS establishment and PPP.

Ionospheric scintillations disrupt the trans-ionospheric satellite signals and cause quandaries in satellite applications typically near the low equatorial sites; GNSS signals are utilized extensively for monitoring such anomalies. This work presents the unique results that confirm the suitability and limitations of a commercial low-cost, GNSS module (Ublox ZED F9P) for amplitude scintillation monitoring from a location in India situated near the EIA crest during the autumnal equinox of 2022 for low to intense amplitude scintillations. Comparison of amplitude scintillation index (S4) and fade rate using concurrent data from a Leica GR50 geodetic receiver and the low-cost module shows fairly good agreement between the results. The findings have practical utility in designing cost, size, and power-efficient GNSS probes using such modules for ionospheric research. Such modules are not a replacement for the traditional receivers but can be utilized to implement a multi-point, autonomous amplitude scintillation monitoring network.

In a multi-GNSS (global navigation satellite system) environment with operational GPS, GLONASS and Galileo Satellites, the Asia–Oceania region is expected to get better benefits of a large number of GNSS satellites for use. However, it is witnessed that during some parts of the day, no GNSS satellite is present above 60° elevation angle from many parts of the earth, including India. Real-time data from India show the regular absence of usable GPS satellites above 60° elevation angles during some parts of the day; addition of GLONASS and Galileo satellites does not improve the situation much. From Burdwan, West Bengal, India at least twice a day, no GNSS satellite is found above 60° elevation angles for more than 30 min. Simulation study for scattered places of India and data from IGS Centres confirm similar observations, except for the extreme northern region. The global scenario also supports these observations, while the individual operator’s country is free from the problem using their own navigational system. The consequences of the problem affect GNSS-based solutions; for locations with obstruction of GNSS signals from low elevation angles, the concurrent occurrence of this incidence poses a threat for seamless GNSS-based navigation through intermittent loss of solution and degraded solution quality. Regional navigation satellite systems (RNSS) help mitigate this problem within the respective service regions. For a large part of the globe, the problem may be allayed using GNSS–RNSS hybrid operation. The result would be important for location-specific GNSS mission planning in strategic, life and safety-critical applications.

Galileo and NavIC, respectively, are two operational global and regional satellite-based navigation systems maintained by civilian authorities. Hybrid operation of a global and a regional system offers advantages for the user community within the service area of the regional system. In view of the signal structure similarity of Galileo and NavIC, hybrid operation of the two systems has been studied from India and surrounding regions to explore the possible complimentary benefits. Based on long-term, real-time observations from two locations within the NavIC central region and validated simulations, Galileo and NavIC constellations were found to supplement each other. In the central region, relatively poor Galileo availability is supplemented by NavIC and in the boundary areas Galileo supports inferior NavIC visibility. The time- and location-dependent low-elevation angle problem for the Galileo satellites is supplemented by NavIC signals transmitted from GEO and GSOs for seamless and improved operation. In terms of typical satellite visibility within the constrained satellite visibility conditions, satellite geometry and signal strength, the Galileo–NavIC hybrid operation offers user benefits over the Indian region as well as over the entire NavIC service area extending from east Africa to west Australia. Real-time data collected from survey grade GNSS receivers and compact GNSS module clearly indicates the improved solution quality of the hybrid operation compared to each of the individual constellations. The results would be beneficial for the user community in exploiting the benefits of the Galileo and NavIC concurrent operation.

High grade or special purpose Global Navigation Satellite System (GNSS) receivers are used for ionosphere monitoring and research. These special kinds of receivers may provide data up to 50 Hz rate. Dual frequency, compact, low cost GNSS receivers which provides raw data is now being used in Single Point or RTK precise point positioning. In this paper, an initiative is described to use these modules for GNSS-based monitoring of ionosphere activities. Here a comparative study between Leica GR50, a high-grade geodetic receiver and Ublox ZED-F9P, a low cost, dual frequency, compact receiver is carried out to explore the potential of such low-cost receivers for ionosphere probing. Studies are carried out on signal strength values in terms of C/N and Sindices. A fixed bias in signal strength values is observed between the data provided by the two receivers which is about 15 dB-Hz in L1 band and 8 dB-Hz in L2 band. Ublox F9P Sindices have limited resolution, but the variation signature follows that for the Leica GR50. The compact module showed the potential for being used as GNSS-based ionospheric monitors with Make and Model specific calibration and with the advantages of cost, size and power efficiency. A GNSS based Ionosphere monitoring Unit (GIMU) integrating small computer, Ublox F9P and wireless data communication module is also proposed for real time, concurrent ionosphere anomaly monitoring using a distributed network of such modules over a geographical region.