TOPES was introduced in the late 1970s, and ran on a PDP-10, using
Tektronix terminals with Plot-10. I haven't seen any specific
information about what operating system was used, but TOPS-10 seems
fairly likely.
TOPES was used at least up until the divestiture. There was a
replacement system under development called MEGS, but I don't know
whether it was completed and deployed.