sir i want to know how to become scientist in isro. what course should i take and how to reach out there.

Hi,

You could appear for GATE and apply for M.Tech at IIST which is connected to ISRO. However that is no guarantee that you will be placed in ISRO. Mostly the recruitment is for post graduates in engineering when I look at the ISRO recruitment careers section. I would advise you to do the same. So you know which course you are best suitable to take up if you were to pursue your PG further.

You can be recruited as a scientist and not through a course. ISRO as such doesnt offer any.

There are many modes through which you can join ISRO as Scientist or Engineer. After 12th or during 12th you can appear for IIST exam ( Indian Institute of Space Science and Technology (IIST), Trivandrum ).
IIST graduates above a certain pass percentage cut off in final B Tech exam are directly absorbed in ISRO system as Scientist/Engineer -SC grade.

To know all about ISRO, you can go through below article -

ISRO: Annual Recruitment of Scientists/Engineers

Hope this helps!!!