Mariner 9
Robdesbois has left out the most important bit:
RCS is only available inside Controlled airspace (it is in fact the only radar service available inside CAS - RIS/RAS being purely outside CAS).
Easy way to remember it:
RIS - we won't tell you what to do
RAS - we'll tell you what to do but you can refuse, in which case you go down to RIS
RCS - do as you're told!