Hi, There are many ways. If you live in India you can write ISAT. It is a test conducted by ISRO. If is one of the tough exam , you can select to do B.Tech in either of the three fields like avionics , earth science and physical science. If you take physical science you can specialise in astrophysics .Other option is to do a Bsc in Physics . After that you can do a integrated PhD offered in Indian Institute of Science. This how to can become a space scientist. Good Luck.