A rush rescue mission to save a NASA space telescope remains grounded, this time because of a last-minute launch problem. Northrop Grumman’s rocket-launching plane took off from the Marshall Islands in the Pacific on Thursday, following weather delays all week. But an issue prevented the team from releasing the Pegasus rocket strapped to the plane’s belly. The rocket holds a three-armed spacecraft built by Katalyst Space Technologies to chase down the Swift Observatory, which will fall out of orbit by October if no help arrives. No new launch date has been set.