Space Shuttle Columbia's STS-75 mission was launched on Launch February 22, 1996. On Flight Day 4 (1996-02-25), an experimental tether was deployed. After being deployed to 19.7km (almost fully deployed) the tether broke. In this video you can see multiple objects moving around the scene. Conspiracy theorists claim these are UFOs but skeptics and NASA scientists claim they are simply ice and debris particles.
NOTE: The title text at the start of this video has been added by someone who obviously thinks NASA is covering up the real explanation. Unfortunately this is the best (i.e. least bastardised) copy of the original footage we have been able to find.