In order to become a astronaut you need a Bachelor's degree from an accredited institution in engineering, biological science, physical science, or mathematics. 

You can choose the course according to your interest. 

According, to the NASA at least three years of related professional experience obtained after degree completion OR at least 1,000 hours pilot-in-command time on jet aircraft. The ability to pass the NASA long-duration astronaut physical. Distant and near visual acuity must be correctable to 20/20 for each eye. The use of glasses is acceptable.

If you want you can appear for JEE exam to get admission in B.tech in aeronautic engineering. Try to get admission in IIT Bombay or IIT Kanpur.

Good Luck!!