Hello, 

Space science or space technology is a broad term in itself which includes astronomy, astrophysics, aeronomy, earth sciences, etc.

You nerd to be expertise in science subjects. These subjects might be pursued from Bachelor's degree after completing 12th from science stream.

Graduate courses can be also taken by ISRO and other institutions such as 4 year B. Tech program. On doing Bachelor's you can seek admission in post graduation in space and science technology. Infact, most professionals working in space researches have their Ph. D degree. This information might help you to achieve your goal :

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Some of the top institutes are IIST, IIT (Chennai, Bombay, Kharagpur, Kanpur), etc.

I hope this is helpful. 

Good luck!!!