In this paper, the authors have attempted to provide a comprehensive account of the Indian Regional Navigation Satellite System (IRNSS). The paper describes the coverage area, the space segment, ground segment, and user segment of IRNSS. The orbital parameters of all seven satellites in the IRNSS constellation have been reported. Some important definitions related to space crafts have been explained. The paper presents the method to estimate the receiver’s position and the algorithm involved. The paper also discusses various sources of error in position estimation. The paper gives a detailed description of the trajectories of all seven satellites in the constellation. The paper presents the Slant Tropospheric Delay (STD) obtained over the National Atmospheric Research Laboratory, Gadanki; National Institute of Oceanography, Goa; Regional Meteorological Centre, Kolkata; Indian Institute of Technology, Bhubaneswar; and Sona Synthetics, Kanakapura, Bangalore.
After the launch of the first indigenous navigation satellite, IRNSS, by India, the precipitation water (PW) has caught the attention of researchers as it poses limitations to the position estimates provided by the navigation satellites, by incorporating delay to the satellite signal. Moreover, knowledge of the upper air meteorological element, like the precipitation water (PW) is essential in understanding cloud microphysics and rainfall dynamics. In this paper the authors have made an attempt to study the PW, along with the cloud liquid water (CLW), and the latent heat (LH) over Salem, a southern suburb in India. The aim of this paper is to estimate precipitation water (PW) from the knowledge of rainfall. Correlations of surface rainfall with these elements have been established. The correlations of the CLW/PW/LH have also been investigated under convective rainfall. The CLW, PW and LH values at 14 levels of the atmosphere, from the Earth’s surface up to a height of 18 km above; and the rainfall values have been obtained from the data product 2A12 of the microwave imager (TMI) onboard the Tropical Rainfall Measuring Mission satellite (TRMM). The surface rainfall and the convective rainfall are found to bear significant correlations with these elements. Thus, it appears that it is possible to estimate these elements from the knowledge of surface rainfall. The findings of this paper will be helpful in validating the IRNSS-retrieved precipitation water. The paper also investigates the influence of sunspot number (SSN) and Total Solar Irradiance (TSI) on rainfall over Salem. The SSN/ TSI data have been obtained from the Solar Influences Data Analysis Centre (SIDC), Royal Observatory of Belgium, and the rainfall data have been obtained from the India Meteorological Department (IMD).