The largest digital camera ever built for a space mission has been painstakingly mosaicked together from 106 separate electronic detectors. The resulting "billion-pixel array" will serve as the super-sensitive 'eye' of ESA's Galaxy-mapping Gaia mission.
More: http://www.esa.int/esaSC/SEMQ9V6TLPG_index_0.html (http://www.esa.int/esaSC/SEMQ9V6TLPG_index_0.html)
(Edit: Added first paragraph and fixed link -- Rick)
Total detector size is 1 metre by half a metre :o :o :o