Hi,

Some of the best IITs for aerospace engineering:

• IIT Bombay
• IIT Madras
• IIT Kanpur

Aerospace Engineering is a 4 year degree course which enables students to learn and work with applications and understand designing of aircrafts, missile technology, defence technology and other things related to space.

You can check cutoff at:

https://engineering.careers360.com/articles/iits-cutoff-for-b-tech-aerospace-engineering

Coming to second part of question, you can get into ISRO my appearing for the entrance examination.

Eligibility for ISRO Recruitment

• Candidates must have qualified B.E/B.Tech or equivalent qualifying degree in first class with an aggregate minimum of 65% marks or CGPA of 6.84 on a scale of 10. ISRO is strict about the CGPA or marks and doesn’t consider anything less than the given criteria. The average of all semesters will be considered for the purpose of CGPA and not one single semester.

For more details:

https://engineering.careers360.com/articles/isro-recruitment#:~:text=Candidates%20must%20have%20qualified%20B.E,less%20than%20the%20given%20criteria.