• SCATSat-1 is an OceanSat-2 follow-up mission, actually a gap-filler mission between OceanSat-2 and -3, under development at ISRO (Indian Space Research Organization) with the objective to continue the global ocean wind vector data acquisition started by the OSCAT (OceanSat-2 Scanning Scatterometer).
• The information of global ocean surface winds is an important ingredient for weather forecasts.
• In particular, a need for global coverage of scatterometer data became evident, when NASA’s SeaWinds scatterometer on the QuikSCAT spacecraft ceased nominal operations in November 2009.

Some background:

• OceanSat-2 of ISRO was launched on September 23, 2009, providing excellent data of its payload when on February 20, 2014, OSCAT experienced an irrecoverable malfunction in its TWTA (Traveling Wave Tube Amplifier) subsystem of the primary chain and of the scan mechanism of the redundant (backup) chain during the end of its design life period (around 4½ years from launch), forcing ISRO to suspend its operation in April 2014.
• During its operational lifetime, OSCAT had demonstrated the importance and significance of the ocean wind vector data in weather modeling and prediction and laid the ground for continuation of the global ocean surface wind vector data acquisition. The OSCAT data were also used by the international community like NASA/JPL, NOAA, KNMI, EUMETSAT and ECMWF for both research and operational purposes.
• ISRO plans to launch the OceanSat-3 and -3A in the timeframe 2018 and 2019, respectively. The payloads of OceanSat-3 will be OSCAT-2 (Ocean Scatterometer-2), a Ku-band pencil beam scatterometer, OCM -3 (Ocean Color Monitor-3), and SSTM (Sea Surface Temp Monitor), an optical radiometer. OCM-3, which is an improvement over OCM-2, will have thirteen narrow spectral bands in the VNIR (Visible and Near Infrared) region. It will have an improved spectral resolution and SNR as compared to OCM-1/2.

Spacecraft:

• SCATSAT-1 is a minisatellite with a mass of ~ 371 kg and a design life of 5 years, configured on the IMS-2 (Indian Mini Satellite-2) spacecraft bus of ISRO. According to Tapan Misra, director of ISRO/SAC, it takes normally about 3 years to build a satellite of this class from scratch. However, the project sourced about 40% of the parts used in SCATSat-1 from spares of previous missions, to complete the development in a year’s time.
• EPS (Electrical Power Subsystem): 2 solar arrays are generating 750 W, 28 Ah Li-ion battery.
• AOCS (Attitude Orbit Control Subsystem): The AOCS uses reaction wheels, magnetic torquers and hydrazine thrusters.
• RF communications: Data transmission in X-band. The on-board SSR (Solid State Recorder) has a capacity of 52 GB.
• TCS (Thermal Control Subsystem): The TCS is passive using MLI (Multi Layer Insulation) blankets, paints and heat pipe embedded panels.

Sensor Complement

OSCAT-2 (Ocean Scatterometer-2)

• The OSCAT-2 instrument onboard SCATSat-1, developed at ISRO/SAC, Ahmedabad, is similar to OSCAT flown onboard OceanSat-2. However, many improvements both in hardware as well as for the onboard signal processor and control software are being implemented, based on the OSCAT experience. The instrument is a pencil beam wind scatterometer operating at Ku-band of 13.515 GHz.