Hello

you can do MTech in IIST after graduating in the field of Aersopace,Avionics,mathematics,chemistry,physics and Earth and Space Sciences.

In IISER you can do PhD in various fields, there are no MTech courses but dual degrees.

To know about IISER check this link: http://www.iisertirupati.ac.in/admissions/phd/

To know about masters in IIST check this : https://www.iist.ac.in/admissions/postgraduate/regular .

Hope this helps.