How to get into iist(Indian institute of space science and technology)?is iit better or iist better in pursuing a undergraduate course in aerospace engineering??how can we get admission in iist??what is the seat matrix and which rank we should get in jee mains or jee advanced??please answer adroitly

Dear student, IIST Admission is organized by Indian Institute of Space Science and Technology. Admission is offered into UG and PG courses in various fields. No entrance exam is organized by the Institute and the admission is provided on the basis of scores of national level exams JEE Main, JEE Advance, GATE, JEST, UGC NET etc.
Next comes the questions of selecting IIST or IIT. IIST is surely a better option. IIST solely focuses on this field and being in IIST you have advantage and higher chances of getting into ISRO or any space related organisation as IIST has strong contacts with them. Also during your graduation you can get internship opportunities in ISRO.
IIT focuses on many branches of engineering not only space, IIST's corriculum is designed only for space and related subjects. The faculty in IIST are the scientists or senior professors who have/had worked with various space organisations. No doubt IITs have provides the best faculties but IIST have some of the well known person.
Seat Matrix

• B.Tech in Aerospace Engineering - 60+6**
  
• B.Tech in Avionics - 60+6**
  
• Dual Degree - 20+2**
  

** Reservation for EWS Category to the extent of 6,6 and 2 seats.

You can check this link for the cut off trend for IIST.

All the best
Hope this helps