YES2 - A Guinness World Record

 The Guinness World Records Certificate  reads (see also the Guinness Book of World Records 2009 edition):

 "The Young Engineers' Satellite 2 (YES2) was launched on board the Foton-M3 microgravity mission on 14 September 2007. On 25 September YES2 unwound an experimental package on a 0.5 mm-thick cable in order to test the principle of returning payloads to Earth without the use of retrorockets. Experimental data show that the cable successfully deployed to its full length of 31.7 km (19.7 miles), the longest manmade structure ever deployed in space."