Hi Vishnu

These are the options available for you :

1 – Appear in JEE Main exam – The first thing to do is to appear in JEE Main entrance exam, clear the exam with ranks upto 2, 24,000 at All India Level. Only if you get rank upto this, you will be eligible to appear in JEE Advanced.

You have to qualify in JEE Advanced exam and then apply in IIST for admission.

The Indian Institute of Space and Technology or IIST offers admission to JEE Advanced qualified candidates.

At IIST, candidates are recruited by Indian Space Research Organisation (ISRO) and that is your call. IIST B.Tech admission 2018

2 – ISRO Career Options – You will have to explore the careers ISRO offer to engineers and then decide which branch of engineering you have to pick, aeronautical or some other.

3 – NASA – You need to check the career options NASA is offering.

Hope this information helps you.

All the best !