Hello Kamalaksh!

Mechanical engineering is a branch in engineering in which you will find the inclusion of both robotics and aerospace engineering. If Mechanical engineering is a set, then aerospace engineering is a subset of MechE. On the other hand, if you emphasise over universities in USA, they also specialize over space robotics in aerospace engineering curriculum but it is rare in Indian colleges.

If you are more interested in robotics, then go for Mech engineering. But if you want to specialize in aeronautics then stay restricted to aerospace engineering. Aerospace engineering will more deal with aerospace specific topics, like propulsion, guidance and aerodynamics, rather than robotics. You can specialize in mechatronics in mechanical engineering which also extends to space control sytems. So the choice lies in your hands.

Hope you understood.