The post for the Technical Assistant is for those having Diploma in Engineering degrees. If you have MSc in Physics, then you can go for the Scientist C posts released by the ISRO. You must check the ICRB website as the notification are released any time of the year with some vacancies.

So do check it and No! You aren't eligible for the Technical Assistant, you are eligible for the Scientist post itself.

To know more about ICRB, visit the link below:

https://www.isro.gov.in/careers

I hope this answer helps. All the very best for your future endeavors!