Ultra-Fast Flash Observatory Pathfinder

The Ultra-Fast Flash Observatory (UFFO) Pathfinder is a space observatory measuring prompt emission of gamma-ray bursts (GRB) both in optical/UV and in X-ray range down to sub-second timescales for the first time. Instead of turning the whole satellite towards GRB location like the Swift Gamma-Ray Burst Mission (that takes about 100 seconds), UFFO employs a slewing mirror telescope approach – the optical path of the telescope is changed by rotation of motorized mirror within ~1 second after burst was detected.

Source: Wikipedia — Ultra-Fast Flash Observatory Pathfinder (CC BY-SA 4.0)