Hello Sundar,
As long as I know about ISRO , it generally select engineers from IIT .
If you want to join ISRO then you have big choices. The highly paid jobs of engineering are following:
Aerospace engineering
Aeronautical engineering
Software engineering
Genetics engineering
Etc .

ISRO basically hires Aerospace, Mechanical, Electrical & CS engineers (including IT maybe).

And if you further break up these 4 engineering courses, you get Industrial, Production, Mechatronics, Metallurgical, Electronics & Telecommunications etc etc.........

It'll be best if you pursue your engineering in Aerospace, Mechanical, CS & Electrical.....of you want to join ISRO.

The degrees which they look for are:-

(1) B. E.
(2) B. Tech.
(3) B. Sc. (Engg.)
(4) Diploma + B. E./B. Tech. (Lateral Entry)
(5) B. Sc. + B. E./B. Tech. (Lateral Entry)
(6) Diploma + AMIE/Grade IETE
(7) B. Sc. + AMIE/Grade IETE

For further enquiry, I think you should check out their website.

https://www.isro.gov.in/

Hope it helps. :-)