Subject: SOHO/LASCO Partial HALO CME 121021 BACKSIDED UCMEO 93001 21023 1830/ 21021 62124 80708 3292/ 189// 323// 40595 21021 61941 92354 ///// ///// 2212/ 99999 PLAIN SOHO/LASCO observed a Partial HALO CME on October 21, 2012. Event is first seen in C2 at 21:24 UT as a loop with cavity and core appearing over the East. The front expands with extensions PA 329-189 degrees for total coverage of 220 degrees in width. The event continues into the C3 field beginning 22:30 to 07:18 UT leaving the C3 field of view at 30Rsun in the East. Time/height measurements were marked to 6 points in C2 with speeds of 334.4 Km/sec at position angle 100 degrees. The event is marked to 13 points in C3. Speeds average through both fields to 594.5 Km/sec at PA 101 degrees. Acceleration 28.77 m/sec^s. SDO/AIA 193 shows emission 19:21-22:15 UT from the far-side over the SE in difference images. STEREO: BEACON Data COR2 B, 22:39 UT, event produces a faint symmetric halo to last frame at 23:54 UT. Preliminary time/height measure gives 633.4 km/sec velocity at LE. EUVI B, 19:41-23:56 still in progress at last frame. An eruptive filament is seen centered at location [S30, E118] with ribbon flaring. COR2 A, 21:24-23:54 still in progress at last frame. Partial halo over the West. Preliminary time/height measure gives 441.0 km/sec velocity at LE. EUVI A, n/a The observation of this event is considered 'GOOD'. 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/2012/121021/ Best regards, Kevin Schenk Solar Heliospheric Observatory EIT and LASCO Operations NASA-Goddard Space Flight Center, USA BT