Tapan Misra

A decade ago, RISAT-1 was launched on this day, 26 April 2012. RISAT-1 was a pathbreaking achievement of Team ISRO. It was not just India’s first SAR satellite in C band, it rewrote SAR technology by introducing two SAR imaging modes that revolutionised SAR technology itself.

The two SAR imaging modes are:

1. Hybrid polarimetry which made possible introduction of polarimetry in any SAR imaging mode like strip map, scan SAR, Spotlight instead of a separate exclusive polarimetric mode.
2. Sliding spotlight which just pushed the boundary of Spotlight imaging. Instead of typical Spotlight imaging over 5 km X 5 km spot, RISAT simply enhanded the spot area by an order to 10 km X 100 km. Just unbelievable.

RISAT-1 had many firsts:

1. World’s first Spotlight SAR imaging with resolution of 0.6 m in C-band. Prior to RISAT-1, no space borne SAR spotlight mode existed in bands lower than X-band. Lower the frequency, the complexity of spotlight SAR increases inversely by square of frequency.
2. India’s first active antenna, that too in space
3. Probably the most complex electronics ever made in ISRO with around 1500 RF subsystems, 314 onboard computers, 600 EPCs, 3000 RF cables, 5000 connectors, 30 km of digital cabling and above all a payload weighing 950 kg and of massive 6mx2m size.
4. Till, RISAT, payload used to ride on satellite. For the first time, satellite was built inside the payload.
5. RISAT was the first successful achievement of bringing private industry as partners instead of vendors. RISAT-1 experiment paved the way for gradual spread of Indian private initiatives in space Industry. Today’s space privatisation had a genesis in RISAT development.
6. Probably the first ISRO payload which can be called truly indigenous, sourcing 99% of components and subsystems in the country itself. To the country’s pride, all 7 types of MMICs, used in hundreds, were developed for the first time in the country at GAETECH.

RISAT-1 was a tribute to famed team work of ISRO, an endeavour which not only required innovative system integration effort but also human management skill. I have a great respect to Shri RN Tyagi, PD of RISAT-1 for deftly marrying human resources with technology innovation.

Rome was never built in a day. We could succeed because scientists like Shri OPN Calla, Shri NS Pillai Shri SS Rana and Dr. SB Sharma laid the foundation of Microwave Remote Sensing Programme, gave indulgence and courage to raw college pass-out like me to build an imaging radar payload as better than the best in the world.

The team was privileged for receiving blessings from Dr. APJ Abdul Kalam during payload development. In fact he only kick started the payload development in SAC in a presentation over lunch in July 2000. I have fond memories of Prof. Yashpal and Dr. PP Kale, Dr. AKS Gopalan, builders of SAC and ISRO, blessing us during launch and unveiling of the first data product.

We were privileged to be appreciated personally by erudite Dr. Manmohan Singh, then Prime Minister of India. I personally feel proud to be part of an achievement which left lasting impression in the realms of Space Technology in India and the world.

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