You do know that "Robotics" is more mechanical/electrical engineering than physics, don't you?
This is getting rather confusing. It seems that you have ambitions in all different directions. While that is OK when one is just starting out, at this stage when you are thinking of jumping into the field in mid-stream, such indecision is not helpful. Do you want to do robotics, or do you want to do physics/astronomy? Decide once and for all, because unlike starting out as as undergraduate, you don't have that "honeymoon" years where you can take a set of intro classes that are shared by those majors.
In addition, most of us can't tell you if it is possible to get into a "MS course" in any field. What you have to do is look find a few schools that offer the field of study that you want to get into, and look at the undergraduate curriculum in that field. Chances are, these are the courses that they assume that you already know by the time you enroll. I don't know how much physics and mathematics you have, but if I were you, I will be concerned, first and foremost, that my education is severely lacking in many of the fundamental requirements to be either an engineer or a physicist.
Once again, I will point to the link I gave you, and it would apply to an engineering graduate programs also, because many of them have qualifying exams as well, even for a Masters program.
I would also ask you to pay attention to what Norman has said. Many of the so-called NASA programs are run not NASA employees, but rather various individuals from a number of institutions that have obtained research fundings. NASA is becoming like a "user facility", where people from other places use their facilities, such as the Hubble telescopes, etc. to do their research work. This is not unlike other scientific facilities such as CERN, Fermilab, synchrotron sources, etc. in which most of the research done are by those from other institutions.
So do not be fooled into thinking that one has to work for NASA to do astronomy/astrophysics work that are being reported by NASA.
Zz.