Hii Satish,

First of all let me tell you, that there are four sub-branches or specializations in Aeronautical engineering:

• Control system and flight dynamics
• Gas dynamics
• Structures
• Space science

One of the most important tool across all these specializations is MATLAB. So,you should have a proper command on it.Apart from MATLAB you can also learn other programming languages such as C and C++.

Apart from programming languages,below are few courses in which you should get specialisation:

• Applied mechanics
• Aircraft structural mechanics
• Composite structures
• Propulsion to different Aircraft and space vehicles
• Aerodynamics
• Aircraft design acoustics
• fluid mechanics

Note:Specialisation in fluid mechanics will help you to get into NASA.

Hope,it helps you!

Good luck