GOES-15 Navigation Anomalies
GOES-15, in service as GOES-West over the Equator at 135 W, has experienced navigation anomalies on each of the past three mornings, September 8, 9 and 10, 2013 (as noted here, for example). Navigation anomalies occur approximately between 0830 and 1100 UTC. GOES Engineers are investigating the source of the anomaly, which can be on the order of 40 km. The animation above is the shortwave infrared from Tuesday 10 September. Animations for 6, 7, 8 and 9 September are below. Note that even the 6 September and 7 September have small navigation issues.
(Update: From SATOPS: NOTE: GOES-15 (West) Image registration (alignment of images to earth grid coordinates) was shifted by approximately 40 kilometers on DOY251 (ed. note: 8 September) from 08:50z to 10:50z and shifted by approximately 25 kilometers on DOY252 & DOY253 (ed. note: 9 and 10 September) from 9:30z to 10:40z. The earth coordinate grid shift was due to a lack of available valid star data for predicting the proper attitude pointing profile around eclipse. The root cause is under investigation.) In other words, the Star Pointer was unable to find enough targets to produce accurate navigation. (Link)
Update, 11 September: The anomalies continued on 11 September, starting after the 0845 UTC image, peaking at the 1000 UTC image, and subsiding by 1045 UTC. Link.
Update, 17 September: Large navigation anomalies were not present overnight.