Hii aspirants
From my point of view for joining isro you should take aeronautical engineering or mechanical engineering.
There are other branches too lije ME,ECE ,CSE.the main thing is that you must be best at what you do .You must get good marks in your studies.
You should get atleast 65 percent in your btech degree.
To get job in ISRO you have to pass exam conducted by ISRO.
Also there should not be any criminal charges against you.
So choose your branch according to your intrest and give your 100 percent in the field you have chosen to join isro.
I hope my answer will be helpful for you.
Good luck

Hello Aspirant,

To join in ISRO aerospace engineering and aeronautical engineering will be a good choice.  And now a days even the CSE and IT engineers have the chances in the software field in ISRO. 

Hope this helps.
Good luck.

Hello Nandini,

You can choose Btech in Civil, Mechanical, Electrical/EC/ENTC, Computer Science, Mechanical+mtech cad/cam, Structural engineering, Aeronautical as well. So it is advisable to choose the branch as per your interest and potential as you have many options.

Good Luck!