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SCATSAT-1 is the Indian Space Research Organisation's (ISRO's) newest Ku-band scatterometer which was launched on 26 September 2016 from ISRO's space-port Sriharikota on-board the PSLV C35 mission. It is an advanced follow-on of OSCAT, ISRO's first Scatterometer in space on-board the Oceansat-2 satellite, which ceased to operate in April 2014. OSCAT had been a globally acclaimed sensor during its lifetime. The data from SCATSAT-1 exhibit superior quality, and will not only serve the operational wind and weather prediction community in the years to come, but also hold the promise of securing a place in the long-term climate data records. SCATSAT-1 is a standalone scatterometer mission atop the Indian Mini Satellite (IMS-2) bus. The scatterometer payload is a two-beam, dual-polarized, conically scanning, pencil beam, real-aperture radar which measures near-surface wind vectors over ocean exploiting Bragg scattering resonance at Ku-band. It has been developed in ISRO's Space Applications Centre, Ahmedabad in less than two and half years to replace OSCAT. Although it inherits the instrument specifications from OSCAT, several enhancements have been made in its hardware as well as in the payload characterization from the purview of miniaturization and performance improvement over OSCAT. This article highlights the hardware improvements, the payload characterization methods devised, and the performance enhancements of SCATSAT-1 over OSCAT. The in-orbit performance of SCATSAT-1 is also discussed. [ABSTRACT FROM AUTHOR]

2Formerly with Space Applications Centre, Indian Space Research Organisation, Ahmedabad 380 015, India The launch of Radar Imaging Satellite (RISAT-1) marked a new chapter in the remote sensing programme of Indian Space Research Organisation (ISRO). RISAT-1, carrying a multi-mode Synthetic Aperture Radar (SAR) system, will provide complementary imaging capability in microwave along with optical images, being obtained from the well-established IRS class of satellites. RISAT-1 supports a variety of resolution and swath requirements. Both conventional stripmap and scanSAR modes are supported, with dual polarization mode of operation. Additionally a quad polarization stripmap mode is provided for availing additional resource classification. In all these modes, resolutions from 3 to 50 m can be achieved with swath ranging from 25 to 223 km. On experimental basis, a sliding spotlight mode is also available. In all the imaging modes, a novel polarimetry mode called circular or hybrid polarimetry can be exercised seamlessly. The system is capable of imaging on either side of the flight track depending upon prior programming of the satellite. The satellite is placed in a Sun-synchronous orbit with 6 am-6 pm equatorial crossing. This orbit configuration is chosen to maximize solar power availability. The satellite has an on-board-solid state recorder for supporting data acquisition beyond ground station visibility. The payload is based on active antenna array technology. Crucial technology elements like C-band MMICs, TR module and miniaturized power supplies have already been developed in India. A pulsed mode near-field test facility has also been developed in-house in order to characterize the payload in the integration laboratory itself. [ABSTRACT FROM AUTHOR]