Dear student,

Changing the board of examination is completely your choice, it has nothing to do with becoming aerospace engineer in ISRO, but before getting admission you must know that you should do your 11th and 12th with Physics, chemistry and Mathematics, these subjects should be there in your examination.

Now, let me tell me what is the way to join ISRO and become aerospace engineer.

After completing your 12th, you have to get admitted in the course of Aerospace engineering in any recognized institutes, obviously getting admitted in top institutes will be better and more valued. AME CET is a national level entrance exam, by performing well in it, you can get top institutes.

After you complete this course, you will get degree of Aerospace Engineering Degree recognized by the All India Council for Technical Education (AICTE), Government of India.

After this, you will have apply for an entrance examination called ICRB which is conducted by ISRO for graduates, based on your score in this you will get post in aerospace engineering department.

I hope this clears your doubts.

You can check more about aerospace engineering by going through the link below.

https://www.careers360.com/courses/aerospace-engineering-course

All the very best!!

You don't need to change your board. But if you want you can change.
For isro you have to work very heard. If you focus on our goal you can do it.
Isto or any other research center is based on your interest of your subject. To modify science and development. Which give good effect.
You can practice the isro requirements exam papers
And also general knowledge is very important. You can also practice general aptitude.
You can also  go for IIST is the pathway to join ISRO for class 12th students. To get admission in IIST, they have to write the JEE Main and Advanced examination and once they are through in Advanced examination, they have to apply separately for IIST and they go through there own selection process. They select students as per their ranks. They take around 140 students every year (60 in Aerospace Engineering, 60 in Electronics and Communication and space sciences)

You can also see the requirements proses
https://engineering.careers360.com/articles/isro-recruitment/amp

All the best. Keep study . Thank you . I hope this answer helps you.