hi,

see you have two options to select at bachelors level to become a space scientist in future.

you have to study physics, chemistry and mathematics, english  as a compulsory subject in 12th course.

once you complete your 12th you have to take admission in b.sc physics or bachelor in engineering / b.tech any of the course.

if you choose b.tech you may take b.tech in IIST in aerospace/ ece , or take admission in nits/ iits/ iiits or any other tier 1 institute in ece, cse / electrical/ mechanical engineering.

students whi has taken b.sc in physics, need to pursue m.sc and phd to get opportunity to work at ISRO, once of the leading space research organization in india.

students of engineering background may apply as scientist B position / ENGINEER at ISRO when recruitment would release.

since you are at early stage focus on your studies and give extra care to study mathematics, physics.

hope it would help.