See ISRO recruits most number of Aerospace/Mechanical/Electrical/Electronics engineering. But in general, the vacancies for the Computer Science and Engineering graduates are also released. I would recommend you to go for the MTech in CSE branch in order to have a better possibility of getting recruited in ISRO.

For getting into ISRO, the most probable place to go for is IIST in order to get recruited. Now the closest field you can go for is the MTech in VLSI & Microsystems/MTech Machine Learning and Computing at IIST and if you have CGPA above 8 then you will be placed directly to ISRO.

Apart from this you can go for the IIT's which will give you a push in your academic background during Personal Interviews. Above everything to get in ISRO, is the knowledge so college don't matter, what matters is your skill and what you learn. So be rigorous with that.

For the IIST official website visit:

https://www.iist.ac.in/admissions/postgraduate/regular

I hope this answer helps. All the very best for your future endeavors!