EOS-08 Gnss-Reflectometry Payload Level-1 Data Product Generation

EOS-08 is an earth observing satellite, injected into 475 km Low Earth $\operatorname{Orbit}($ LEO) with 37° inclination, on $16{ }^{\text {th }}$ August 2024. GNSS Reflectometry (GNSS-R) payload on-board EOS-08 is ISRO’s first GNSS-R mission and first of its kind with dual frequency (L1 & L5) operation utilizing both Global Positioning System(GPS) and Indian Regional Navigation Satellite System(IRNSS) constellations. GNSS-R payload has two major subsystems viz. Precise Orbit Determination (POD) subsystem (comprising of two zenith antennas to receive direct GNSS signal) and Reflectometry subsystem (comprising of one nadir antenna to receive reflected signals). The direct and reflected L1 & L5 IF signals recorded onboard along with auxiliary information are send on ground for further processing. The aim of this paper is to describe generation of Level-1 data products from the sensor raw data. Data processing strategy for specular point estimation and computation of various radiometric parameters along with the product format has been discussed is this paper.