As covered by [Arstechnica]:
T'is the season for rockets, both SpaceX and ArianeSpace are both going to be launching tormorrow on Wednesday, approximately 10 to 11 hours as of this post, with SpaceX's scheduled liftoff just 15 minutes after the Ariane 5's.
ArianeSpace will be launching from Kourou in French Guiana, over the Atlantic Ocean and will be sending four Galileo satellites into medium Earth orbit for the European Commision.
SpaceX is launching from Vandenberg Air Force Base in southern California and deploying 10 Iridium NEXT satellites, in addition to yet another Block 5 landing they've redeployed the droneship Mr. Steven with a newly equipped larger net, and will attempt to catch one half of the rockets payload fairing.
You can watch the ArianeSpace livestream [here], and the SpaceX livestream [here].