ISRO mostly recruits Engineers from the field of :

• Mechanical Engineering (AEROSPACE ENGINEERING included)
• Electronics and Electrical Engineering
• Civil Engineering
• Architecture

The vacancies usually go for BE/BTech and some need MTech.

Now as you are interested in Physics then you have to ways:

• Go for 4 years BSC Physics program and then you can get admission in IIST MSc Astrophysics and Astronomy. If you >8.0 GPA then you get directly recruited in it.
• Another way is you go for BSc and MSc or BSc+MSc course which will take 5 years. Then you can go for MTech courses in IIST which can also land you a job in ISRO.
• Some times ISRO releases MSc Physics recruitment notification but you have to visit the ISRO site regularly and check it. Its not regular.

If you want to for Physics then also BARC is a great option for Physics MSc graduates. The work profile and salary are also great. So don't worry and pursue your passion.

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

Dear Aspirant,

to become a Physicist at ISRO candidates are first and foremost required to have an educational background in the fields of either pure science or engineering. Interested candidates can have either of the background. Next, candidates are recruited, are required to posses a PhD degree in Astronomy, Physics and Mathematics along with engineers in streams of Mechanical, Electrical, Electronics and Computer Science Engineering.