Congrats on securing a great rank Sumanth, with a rank of 3203 any IIT will be possible for you if you don't have a preferred branch or location. 

Coming to IIST, it maybe a bit tough because the number of seats is less in that college ( just 140 ) and its a very reputed institute for space enthusiasts.

I suggest you do participate in JoSAA counselling sessions and you will surely end up with an IIT. Best of luck