Michael Schumacher drove in his first open wheeled race series (the European Formula Ford 1600 series) the same year Senna won his first World Title for McLaren,1988.
Senna had already won 6 races and finished in the top 3 on 28 occasions in total and had put his car on pole 16 times.
I think the wider audience, including Schumacher would have been well aware of who Senna was by then.