UPDATE 1-NASA plans launch invitations to Twittering media

* NASA invitation-only event for new media planned * Astronauts Twittering from orbit * TweetUp slated for August launch (Updates number of invitations, adds bloggers) By Irene Klotz CAPE CANAVERAL, Fla., June 1 (Reuters) - NASA, which has tiptoed into the new world of social media with Twittering astronauts and Facebooking rovers, is taking the next step with an