Subject: SOHO/LASCO Partial HALO CME 110407 BACKSIDED UCMEO 93001 10408 2030/ 10407 62236 80930 2032/ 131// 113// 30270 ///// ///// ///// ///// ///// ///// 99999 PLAIN SOHO/LASCO observed a Partial HALO CME on April 7, 2011. Event is first seen in C2 at 22:36 UT as a slow elevating prominence feature on the west limb centered at PA 260 degrees quickly followed by an impulsive split loop expanding counterclockwise. The front expands and develops. Material spans PA 203-131 degrees for a total coverage of 288 degrees over the north and west hemispheres. The event continues into the C3 field beginning 00:30 UT to 09:30 UT out to 25.37 Rsun. Time/height measurements were marked to 14 points in C2 with speeds of 143.4 Km/sec at position angle 296 degrees. The event is marked to 13 points in C3 where it slightly accelerates. Speeds average through both fields to 270.2 Km/sec at PA 295 degrees. STEREO COR2 B shows a large cme beginning 21:39 UT in the NE field with an expanding cap in the east and southeast. COR2 A shows the cme is progress in the west and southwest field but misses the beginning due to a data gap. EUVI 195 A shows elevated filament material and dimming in the NE field at 16:45 UT along with a NPCF and low scale activity from the 2 ARs near the limb in the NW and SW areas. EUVI beacon data goes into gap at 21:35 UT and may have missed part of the cause of the halo. SDO/AIA does not show any evidence of the event on disk. These events are most probably the cause of the HALO event seen in LASCO. The observation of this event is considered 'FAIR'. This CME is determined a BACKSIDED event. Images and movies and time/height information for this event is available on the web at: http://umbra.nascom.nasa.gov/lasco/observations/halo/2011/110407/ Best regards, Kevin Schenk Solar Heliospheric Observatory EIT and LASCO Operations NASA-Goddard Space Flight Center, USA BT