Proba-3 will use laser for millimeter precision in space

ESA's double-spacecraft precision formation flying mission, Proba-3, is due to be launched from India on 4 December. The spacecraft pair will employ a set of positioning technologies to keep formation in space and this image shows the most precise: a laser shone from one platform to a retroreflector on the other. The reflected laser beam will provide positioning precision down to a single millimeter.