Core Radar Electronics and Industry Role in ISRO’s Current and Future Microwave Remote Sensing Payloads

Paper number

IAC-08.B1.3.8

Author

Mr. Nilesh Desai, Space Applications Centre (SAC), ISRO, India

Coauthor

Mr. Tapan Misra, Indian Space Research Organization (ISRO),SAC, India

Coauthor

Mr. Rajkumar Arora, Indian Space Research Organization (ISRO),SAC, India

Coauthor

Mr. Virendra Gujraty, Indian Space Research Organization (ISRO),SAC, India

Coauthor

Mr. Surindersingh Rana, Indian Space Research Organization (ISRO),SAC, India

Year

2008

Abstract

                   
Keywords : Microwave, Radar, SAR, Scatterometer, MADRAS, Oceansat-II, RISAT-1, Megha Tropiques, industry, core radar electronics


Since its inception in 1985, Microwave Remote Sensing Programme (MRSP) of SAC/ISRO is aimed at designing microwave sensors and enhancing the capabilities of ISRO’s Earth Observation (EO) missions. A C-band Airborne Synthetic Aperture Radar (ASAR) and a Multi frequency Scanning Microwave Radiometer (MSMR) payload for Oceansat-I (IRS-P4) were developed in 1990s. Currently flight model development activities are nearing completion for ISRO’s four major EO missions involving microwave sensors. RISAT-1 satellite, scheduled for launch in 2009 AD, consists of an active antenna based C-band multimode, multipolarisation SAR, with an experimental one meter sliding spotlight mode with 100 Kms azimuth extent. The Ku-band Pencil beam Scanning Scatterometer payload onboard Oceansat-II, is now under integration and will be ready for delivery and launch by mid-2008. Megha-Tropiques (MT) mission, a significant collaborative science project between ISRO, India and CNES, France, carries 
Microwave Analysis and Detection of Rain and Atmospheric Structures (MADRAS) imaging radiometer, and is scheduled for launch in 2009. C-band Airborne SAR has been replaced with an airborne SAR for Disaster Management (DMSAR), with imaging capabilities of 1m to 30m resolutions, with swath coverage of 6km to 75 kms. 

One major feature of these developments is that the hardware for these microwave sensors have been developed with core radar electronics concept, in which all the digital subsystem hardware will be based on programmable and reconfigurable elements like FPGA, microcontroller etc., so that their configuration can be easily changed by changing the associated firmware / software. For RF subsystems as well, the core electronics modules have been standardized. Thus, same RF and digital hardware sub-units / modules are utilized to build different microwave radar sensors. The emphasis was on development of less number of variants of subsystems but more variants of systems. This concept was conclusively validated, when RISAT-1 developmental model hardware was converted very effortlessly to DMSAR within two months. Thus, RISAT-1 SAR designs with requisite modifications are being utilized for the concurrent development of all the other sensors.

The other major striking feature is that a new beginning has been made in Payload development history in ISRO during this decade (2000 AD onwards) by participation of the local indigenous industries in a big and substantial manner in the realization of RISAT-1 SAR and other microwave payloads. The proof-of-the concept and Flight Models of various new and challenging technology elements for RISAT-1 SAR like phased array active antenna with electronic beam steering, high power (~ 30 watts) single board ultra-high speed I/Q digitizers (250 MHz sampling), FPGA based wideband digital chirp generator and onboard Block Adaptive Quantiser (BAQ) data compression, distributed embedded controller for active antenna, different types of MMICs, Miniaturised C-band TR-module and Pulsed Power supplies, Dual Polarized printed antenna, Tile Electronics involving Onboard Controller ASIC, Tile Control and TR Control units, complex frequency generator, wide bandwidth receiver etc. have been realized with the active participation and collaboration of local and indigenous public and private sector industries. Indigenous MMIC fabrication line has been qualified at GAETEC foundry. The developmental models of onboard baseband subsystems, EGSE elements like Ground Check-Out units for all payloads, Quick look and Near-Real Time SAR digital processors for DMSAR and RISAT-1 SAR etc. have also been realized with the involvement of private and public sector industries. Most of these high-end technology developments for RISAT-1 and other missions involving microwave sensor were possible only with active industry participation and close interface. Instead of the standard approach of treating industry just as supplier, partnership approach was adopted in which in-house capabilities both in terms of human resources and facilities were provided to industry partners to fill up the gaps. The necessary laboratories, clean rooms and other environmental facilities have also been set-up and operationalised at these industries.

RISAT-1 follow-on mission will carry a L-band Multi-polarization SAR operating in stripmap mode (5m, 100Km swath) and will mainly cater to applications related to agriculture and Soil moisture analysis. In consonance with various application requirements and projections, ISRO has also planned a number of other missions involving microwave sensors for LEO orbits like X-Band Agile Small Satellite SAR, 35 GHz Ka-band radar Altimeter, L-band Synthetic Aperture Radiometer, Multi-channel Polarimetric radiometer and MM Wave sounders. Since SAR payloads will remain the main workhorses of Indian Microwave Remote sensing programme, the same approach of core radar electronics and industry participation is also proposed for all these future missions involving microwave sensors. 

This paper describes the challenges involved and ISRO’s success in addressing these challenges of microwave SAR and other payload realization with the twin concepts of core radar electronics and industry participation. It also outlines the approach for ISRO’s future missions involving microwave sensors, which will also feed into ISRO’s main aim of establishing and re-inventing itself as mainly a research organization for advanced technologies for aerospace sector while guiding the Private Indian aerospace industries for producing and maintaining continuity of its current and future routine satellite missions involving microwave remote sensing payloads. 

Abstract document

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