hi,

see the eligibility criteria for gate exam is, candidates must be in final year of b.tech/ b.e of engineering or have passed the engineering course in any of the stream, or students of b.sc final year or passed or m.sc passed or final year candidates are also eligible to apply.

so irrespective of your bachelors degree stream you are eligible to participate in GATE exam from Gate aerospace engineering paper.

hope it would help.