In Bhagalpur, Mitra began school at the Bhagalpore Zilla School. Around 1897–1898, when aged six or seven, his interest in atomospheric science began after hearing the story of Ramchandra Chatterjee, a Bengali aeronaut who a year before Mitra's birth, on 4 May 1889, had become the first Indian to make a solo balloon flight. The story prompted Mitra to ask his elder brother Satish Kumar about the principles of lighter-than-air flight; his brother explained as best as he could. A few years afterwards, both of Mitra's elder brothers died; following this harsh blow, Joykrishna soon suffered a paralytic attack and became an invalid. Despite the family's increasing financial burdens, Saratkumari managed to educate her two surviving sons. During his childhood and adolescence, Mitra nurtured his interest in science through reading popular scientific articles by leading Bengali scientists, including some by Jagadish Chandra Bose. After passing his examinations from the Bhagalpore Zilla school, Mitra was admitted to the FA (intermediate-level) program at the T.N.J. College; his father Joykrishna died shortly after.