The German has continued racing throughout the previous decade but hasn't participated in a Formula 1 car in that period as he makes his return at Spa.
Lotterer told reporters: "To have the chance to drive is something special; I think not everybody has the chance to jump in like that.
"It's a big challenge. I think I have to be quite brave to jump in like this in the middle of the season."
Lotterer will replace Kamui Kobayashi for Catherham ahead of the Belgian Grand Prix this weekend.