GOES-13 (East) has experienced an anomaly at 0340 GMT on 22 September 2012 and fell into a safe/storage mode. In not now being pointed at the Earth, it is unable to generate imagery of the planet. The reserve spacecraft GOES-14 is being brought in to replace it for the Goes East weather montioring function for the US NOAA (National Oceanic and Atmospheric Administration).
UPDATE on 11 June: GOES 13 was recovered to full service on 10 June. The fault was blamed on a micrometeoroid strike onto its solar array arm on 22 May.