Hey Semantha, If you want to join in ISRO you can join in any stream of engineering.For a mission various stream engineers work together.So, choose the one in which you have interest and passion.
If you can join in IIST you can directly into ISRO after your B.tech/Dual Degree.
These are courses in IIST
4-Year B.Tech. ( Aerospace Engineering )
4-Year B.Tech. (Electronics and Communication Engineering (Avionics))
5-Year Dual Degree (B.Tech. + Master of Science/Master of Technology)
All the Best!
Regular exam updates, QnA, Predictors, College Applications & E-books now on your Mobile