Subject: SOHO/LASCO HALO CME 120127 BACKSIDED UCMEO 93001 20127 1930/ 20127 61827 91930 3122/ 311// 333// 52405 20127 61742 81905 48533 11402 1112/ 99999 PLAIN SOHO/LASCO observed a full asymmetric HALO CME on January 27, 2012. Event is first seen in C2 at 18:27 UT as a bright loop over NW at pa 312 in progress with LE at 3.3 Rsun. The event develops to an asymmetric HALO with deep cavity. The event continues into the C3 field beginning 18:32-19:30 UT last frame in progress before a DSN data gap period with LE to 15 Rsun at pa 324. Proton emission is seem in the white light images. Time/height measurements were marked to 3 points in C2 with speeds of 2132.5 Km/sec at position angle 306 degrees. The event is marked to 6 points in C3. Speeds average through both fields to 2407.9 Km/sec at PA 306 degrees. Acceleration 50.22 m/sec^s. SDO/AIA shows a material rising over the NW limb beginning 17:42 UT with eruption producing a wave across the North and West hemispheres at 18:18 UT and post arcade loops seen over limb. NOAA data shows an X1.7 Xray flare. Proton flux at >100 MeV level is reported above the Storm Level threshold. STEREO: Beacon data COR2 B, 18:25-19:55 UT. Loop over North Pole develops full halo. Preliminary time/height measure gives 2271.8 km/sec velocity at LE. EUVI B, 18:16 UT wave seen propagating over North hemisphere from far side. COR2 A, 18:24-19:32 UT. Bright loop begins over east developsto full asymmetric halo. Preliminary time/height measure gives 2299.6 km/sec velocity at LE. EUVI A, 17:45-19:05 UT. Flare of AR 11402 in NE located at [N33W85] with wave spanning the face of the disk in view with post loop arcade. The observation of this event is considered 'EXCEPTIONAL'. 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/2012/120127/ Best regards, Kevin Schenk Solar Heliospheric Observatory EIT and LASCO Operations NASA-Goddard Space Flight Center, USA BT