Hi Deepak of course you can join MSc in space science after engineering in mechanical engineering and one of the topmost institutes to do this would be from Indian Institute of Space Science and Technology.
You need to have at least 60% aggregate in your be aura 6.5 out of 10 CGPA to be eligible for this course. Also you need to give entrance exams like Gate, UGC net and J e s t exams with a valid score to get admission for this course