Prof. Deepak B Vaidya was a Faculty member of Physics Department, Gujrat College, Ahmedabad during 70's and 80's and was a part of the research group which had interest in light scattering effects of colloidal liquids. He used to frequently visit Physical Research Laboratory (PRL) Ahmedabad when I was a PhD student there (in 80's). He was keenly involved with the Infrared Group of PRL and participated in most of the research activities undertaken by Prof. JN Desai. He used to visit Mt. Abu for participating in the observations of Comet Halley.
After I joined IUCAA, Pune in 1990, he was a frequent visitor to IUCAA as a Visiting Associate and I had very strong collaboration with him on modeling of dust in Astrophysical environment like interstellar medium; comets; laboratory studies of light scattering etc. We had participated in several national level meetings/workshops on interstellar dust and its modeling where all electromagnetic bands from UV; Optical and IR were covered. We also introduced voids and other materials/combinations of silicates/graphites etc into our dust models to explain the light scattering observations of various astrophysical phenomena. Our international collaborators were spread from US; UK; Germany; Russia; Japan etc.
We had also attended a few international conferences on Dust including the one at Estes Park, Colorado, USA where during a plenary session, Prof. BT Draine appreciated our dust models research. Infact during 2019 he was invited to USA by Prof. Ludmila Kolokolva (known for her research on comets) for a full month's stay -- but his doctors advised him against any travel given his deteriorating health.
During almost three decades of his visits to IUCAA, I remember our evening discussions and daytime collaborations which resulted in at least two dozens of publications (mostly in International refereed journals).
Our families also were very close and met each other frequently at Ahmedabad including the last visit in 2020 just before the pandemic.
Those who have met him in the past -- would remember his pleasant smile and humble nature!
I wish his soul Rest in Peace and give courage to his wife Meeraben to go through these difficult times.
Ranjan Gupta
IUCAA
Pune