I met Rajaji for the first time in 1982 at the ICOBAN conference at TIFR, but really came to know him after 1986 when I joined Matscience. He was responsible for my joining Matscience. It was Rajaji's letter to my collaborator Rajat Bhaduri which started the ball rolling for my move to join Matscience. By the time I joined Rajaji had already collected a formidable group of young people, especially in the area of High Energy Physics Phenomenology. As a new recruit I was still groping in the dark when Rajaji called Anjan Joshipura and me together for a discussion on a paper by Bethe on Neutrino Oscillations. That marked the beginning of a life long tryst with Neutrino Physics. All through the turbulant period in the late eighties, which affected Rajaji the most, he never stopped encouraging me and my students Indumathi and Ravindran in our research pursuits.
Again in mid nineties he brought me back to neutrino physics after a few year break when I was worked on anyons and fractional statistics. Together with Uma Sankar and Mohan Narayan we wrote many papers analysing the data from solar and atmospheric neutrinos in realistic three generation framework for the first time. A little later in 1997, he along with Mohan Narayan and Uma Sankar wrote the important paper on the result of CHOOZ experiment looking at neutrino oscillations over a short lenght scale. This paper for
the first time identified an important parameter to be tiny; a result the experimental paper had missed in the first version but corrrected later without giving the credit.. After Indumathi joined in 1998, we wrote several paper on the neutrinos from supernove again in the realistic three generation framework; again these were among the first papers to use the full realistic frame work.
All through 90s, Rajaji was thinking about setting up an underground neutrino observatory in India. He realised the pioneering work that was done in the KGF underground laboratory had to be continued but in a different location since the KGF mines were not available. The idea was cemented in 2000 during the WHEPP meeting at IMSc. From then till his last breath, Rajaji was pushing himself and all of us towards the goal of creating the neutrino observatory, INO. We worked on the physics goals of the ICAL detector, one of the most massive detector any where. More importantly, Rajaji also got involved in the search for a suitable site defying his age. He was already close to 70 when we were travelling in the remote mountain areas of Tamil Nadu as well as in the Darjeeling Himalayas. He was present in the discussions with officials of various ministries, presentations for clearances. There was not one aspect of this projecct that was not touched by him. His energy and optimism provided the needed encouragement to all of us even during the most depressing moments and kept us going. He canvassed vigorously for this ambitious project - we went to schools, colleges, held meetings in some tea shops with public talking about the science and the benefits of the project. Unfortunately it has not seen the light of the day yet. His last email that I received on 27th may was indeed about INO in which he was optimistic that INO will find a suitable home!
Rajaji was also quite daring and did not hesitate to speculate or take risks on some important issues when required. Few years ago, I questioned him about the origin of the so called Kolar events and asked him if it could be due to dark matter decay, he immediately jumped at the possibility. He knew these anamolous events since late 80s and had even tried to explain it. Within a few hours we had worked out few details and the paper was written in matter of couple of days. Even though we later realised that the idea could cause problems else where, may even be wrong, it still remains a tantalising possibility.
I was fortunate to watch Rajaji from close quarters and learn life lessons-an exemplary teacher who is refreshingly direct, llively, honest and caring. I will miss him.