“The five Olympic Rings are launched into space carried by four balloons. By the end of the Ceremony, the Rings will have reached the stratosphere … A blue box attached to the Olympic Rings contains a camera, which relays video of the journey to the Stadium screens, and a spot tracker will transmit their position to a satellite every 10 minutes”

2012 Summer Olympics in London: During the London 2012 Olympics Opening Ceremony we saw an image of the Olympic rings against the curve of the planet. Was this image really from one of the balloons released at the start of the ceremony, and how did they do it? - Quora