Hii,

ISRO is a group of All engineers working together for the better future. There are software engineers, Mechanical, Electrical, Electronics and all. No need to worry about the branch. ISRO Generally recruits students from IIT's and NIT's. Even if you are not from IIT'S and NIT's you can still achieve that. ISRO also recruits directly.if there are any vacancies left ISRO will post on their official Website. Students need to check and apply for the position.

Isro recruits students from mechanical , electrical, computer science, electronics, automobiles etc. Programming and knowledge of chips  boards , microchips etc : other than the knowledge of machines is also required now in ISRO .

Getting an admission at IIST ( INDIAN INSTITUTE OF SPACE SCIENCE AND TECHNOLOGY) is an easiest ticket for any student to get a job at ISRO.  You can also give ICRB ( INDIAN CENTRALISED RECRUITMENT) exam . From IIST if a student have gpa of 7.5 and above are directyl absorbed into ISRO . The procedure can be found at IIST official website.

Hello,
An undergraduate degree in cse/ece/eee/mechanical/aeronautical engineering, leads you to your dream. It is going to be a tough route, but if you have what it takes, then you can definitely reach there.
Go through the link below, to know more-
https://www.isro.gov.in/careers
https://nasajobs.nasa.gov/jobs/default.htm
Good Luck!

You can go gor electronic or computer science as well. However if you're more interested towards  research based project you must go for the option of electronics and communication only. Its a very good branch and has very much scope in the recent era. Good luck!