Learning from my career and the building of India’s first SAR

Tapan Misra

When India’s first C -band Airborne SAR (Synthetic Aperture Radar) was ready for its first test flight, I was thrown out of the team by a three-line office order. After all, many thought that the instrument would work just like that and the credit was a low hanging fruit, just to be picked by anybody.

Recently I was asked: What is the essence I learnt from my long technical career? The question set me into reflecting on my 37 year-old past, still very fresh to me as if the things happened yesterday.

The prizes which I received periodically had one common denomination – derision in different avatars. When we used to showcase 300 meter resolution, dull SLAR (Side Looking Airborne Radar) images, captured from a height of 3 km, with the instrument mounted on a second World War vintage Dakota DC-3, senior people used to laugh at my pride in our work. Ha ha! IRS 1A gave one order a sharper image from an altitude of 840 km.

When India’s first C -band Airborne SAR (Synthetic Aperture Radar) was ready for its first test flight, I was thrown out of the team by a three-line office order. After all, many thought that the instrument would work just like that and the credit was a low hanging fruit, just to be picked by anybody. I was declared persona non grata at the airport. I used to spend Rs. 30 daily ( a princely sum in those days!), to go to the airport on my faithful Hamara Bajaj scooter and wait at a far distance. I could see the derision, barely concealed, on the faces of my colleagues bubbling with enthusiasm for almost scrambling towards the credit of building India’s first Airborne SAR. It was another matter that ASAR burnt 52 times in flight and I was called upon to the arena, already botched by many stomping footsteps. When ASAR worked, against all the hopes, there was hardly anybody around to share the credit! It was India’s first SAR and India was the fifth country to have this credit.

When we were building our first spaceborne microwave radiometer, there was a decision not to import the blackbody targets. The price of the imported blackbody was nearly the same as the payload cost. Those who were pursuing the file to import from UK Met, promptly vanished and I was dragged into building the microwave blackbody targets in-house for calibrating the radiometer. I knew nothing about blackbody targets. Still, we built it. I used to struggle to move these 150 kg solid metal structures from one lab to another, one floor to another, people used to laugh at me by keeping a safe distance. The cryogenic tubing in one of the blackbody targets was stabbed mysteriously in the thermovac. I could sense the glee concealed in the eyes of some of my colleagues when we were struggling to repair the tubes in the thermovac without damaging the heaters and other control networks. It was another matter that our radiometer payload was the only radiometer whose ground calibration never needed to be updated while in space.

The SAR processor for ASAR from our sister group had much to be desired. The team was not allowed to put their best for some reason. Exasperated, I borrowed an 8 CPU XEON machine from CMC, learnt C language from Kernighan-Richie, wrote/dictated the software. A new experience for a hardware engineer. When we used to struggle to extract data from HDDTR (High Density Digital Tape Recorder – a relic in today’s technology!), my colleagues used to look askance at me as if I had gone mad – I could have easily passed the buck. Instead, I unnecessarily shouldered responsibility.

The result was a SAR processor which could process Airborne SAR data without an antenna stabilisation system and under any conceivable weather disturbances. We received a couple of Patents and copyrights for this processor.

I was fighting tooth and nail to introduce sliding spotlight and hybrid polarimetry in RISAT-1. For all technical arguments in their favour and my contention that their introduction is just a matter of tweaking on-board software, I was met with a counter argument that no other space agency has those modes in their spaceborne SARs. The common derision smacked question used to be thrown at me – “Do you think that others are fools?” I had no answer, but I won somehow. The result was: after RISAT-1, these modes have become mandatory for present day spaceborne SARs.

I was promoted gloriously from the position of Director, SAC to the sinecure position of Sr. Advisor to force me out of ISRO by humiliating me. After all, why should perpetrators be compelled to interact daily with the eyesore of the surviving victim of poisoning and living witness? The words were spread from powers that be themselves that nobody should cooperate with me. Still some boys defied the diktat and some were shown their places for the crime.

Surprisingly, the remaining two years at the fag end of my career were the busiest, engaging myself intellectually in research, teaching and writing. The irony of life, somebody wants you to turn fossil, but you come out with extra life.

I take justifiable pride in getting two patents during this “Vanvas” (exile) on two diametrically contrasting subjects.

The first one was on a novel algorithm of a new method of very high data compression of hyperspectral imageries and a corollary algorithm of single pixel classification of hyper spectral data onboard. This invention is going to remove the greatest bottleneck of utilising hyper spectral data.

The second one is for the invention of a strip map SAR system with digital beam forming, with spotlight mode-like resolution. This system concept is of a new SAR architecture of the future and it will bring down the cost of SAR data by an order.

I learnt through trials and tribulations that one of the greatest motivating factor in life is the derision of your colleagues, people close to you at your short comings , at your failures and at your sincere efforts. It brings out the best in you and steels your determination to make a mark.

Tapan Misra is a distinguished scientist. He was Director Space Application Centre and has the credit for building the Indian SAR.

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