The 32-year-old German was called up to replace Kamui Kobayashi for the Belgian race earlier this week, with Caterham saying his experience and feedback would help their development push.
Although Lotterer has not driven F1 machinery since testing for Jaguar in 2001 and '02, he has competed regularly in single seaters in Japan's Super Formula series - winning the title in 2011 - and has an exceptional pedigree in sportscars, having won the Le Mans 24 Hours three times as a factory Audi driver.
"It is a big challenge to come in like that [at the] last minute," he said in an exclusive interview with The Official F1® App, "but to do an F1 race is always something that I wanted to do.
"I grew up in Belgium, I know Spa very well so I thought ‘lets do it'. I hope I can help Caterham to move forward.
"I don't know if you can expect a lot from me, but I'm ready to give everything and go flat out."