http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=34176

Rosetta -Y wing successfully passes the deployment test
European Space Agency
November 7, 2003

Kourou, French Guiana

After the electrical and mechanical connections for the -Y wing of the solar array had been made by the combined Dutch Space and Alenia team, it was finally time for the deployment test. After six sequential popping noises made by the thermal knives the - Y wing of the solar array, supported by the deployment rig, slid majestically open.

The deployment test was deemed successful and the -Y wing is now ready to fly.