ISRO picked up lander in the darkness of lunar night - first time in the history of lunar exploration
Today ISRO posted the image of Chandrayaan-3 lander, Vikram, resting in the pitched darkness of lunar night. Vikram was imaged by polarimetric DF-SAR (Dual Frequency SAR) on board Chandrayaan 2. My heart beat jumped at the very sight of the image as I was fortunate to be at the right time, to lead the design and development of this payload DF-SAR. Vikram was identified in double bounce signature (Red colour) of polarimetric SAR in the high resolution mode of 2 m. resolutionn.
NASA provided S band mini SAR onboard Chandrayaan-1 in 2008. It was considered a marvel of engineering and nobody from ISRO was allowed a peep inside the closed packages. So it was but natural for ISRO to invite them for providing the SAR for Chandrayaan 2 orbiter. Nobody can refute the argument of having the continuity of data records with continuity of payload. But having built RISAT-1, I was determined to bag the payload, albeit with much better SAR configuration.
It was November 2012. I was pitching for our proposal before a daunting committee, chaired by Prof. U R Rao. Those who faced pugnacious questioning by Prof. Rao, can vouch for the tremors I was feeling in my heart, while facing him.
I pleaded for polarimetric L and S band SAR with capability of volumetric estimation of dirty ice in the depths of polar craters in comparison to single frequency SAR from NASA, which can identify only the presence or absence of water. Rao Saab was blunt. He was willing to allot 11.5 kg mass, same as NASA's miniSAR. I pleaded that we will have 4 times the NASA hardware and I pleaded for at least 4 times the mass budget. Finally, Rao saab gave his verdict with his typical dead pan visage: 15 kg, take it or leave it. I was desperate enough to agree to this atrocious number. Only 6 months before, we launched RISAT-1 with a mass of 950 kg. I knew the 15 kg mass budget was sheer impossibility. I returned with a fear that I had probably bitten more than what I can chew.
Rest is history. Our team rose to the challenge. We built dual frequency SAR antenna sharing the same aperture. The rectangular S band patch was printed inside rectangle shaped annuar L band patch. We built ISRO's first class-F GAN ( Gallium Nitride) power amplifier to reach highest possible power efficiency with very reduced mass. Our digital team built very miniaturised package, clubbing functionalities of three packages of RISAT 1. It was essentially a mad weight loss programme we imposed on ourselves. Only possessed team can embark on this crazy path. We delivered DF SAR finally with 16.5 kg mass, exceeding the atrocious mass budget by 10%. Rest is history. I learnt a valuable lesson from Prof. U R Rao : set a standard for yourselves, better than the best and put your hearts in the game to achieve what you have set for yourselves.
