The first autonomous CSO, i.e. ELISA, is already in operation since June 2009. It has been designed and built in collaboration between Femto-ST Institute, the National Physical Laboratory (UK) and TimeTech GmbH (D).
Since April 2012, ELISA is installed in the new ESA Deep Space Station (DS3) in Malargüe (Argentina). The tests validate in situ performances of the CSO.