Hi, BSc from DU is a good course and university to pursue from BUT to become a scientist you need to have B.Tech in Mechanical, Chemical. Electrical, Computers, Chemistry etc.
Or after Bsc: : If you are a top 5000 or so AIR holder in IIT JEE, or a national level topper in plus 2 exams, you can more or less be sure to get an interview call for UG degree anywhere in India, including IIST, IISc, IISERs etc. I recommend to check individual websites, as some of them conduct their own admission tests. IIST has a tie up with ISRO, so that their students get jobs in ISRO right after graduation.
Later on you will be required to have PhD.
Let me know incase you need any other guidance.
All the best.