Arianespace will be launching GSAT-8 of ISRO on 2:08 a.m. (IST) on May 21, 2011. The launch site is Spaceport (Guiana Space Center ). All the pre-launch activities are progressing satisfactorily.
GSAT-1 was weighing 1530 kg and was launched by GSLV-D1 by ISRO, while GSLV-8 weighs 3100 kg.
Best of Luck to Arianspace and ISRO.