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. While in flight, the team observed a warning in the stream of data and decided against releasing the Pegasus rocket strapped to the plane's belly, the company said. It was not immediately clear whether the warning came from the rocket or the plane.

The rocket holds a three-armed robotic spacecraft built by Katalyst Space Technologies to capture the Swift Observatory, which will come crashing down by October if no help arrives. No new launch date has been set.

NASA paused Swift's science operations earlier this year to preserve its orbit as long as possible. It has detected thousands of gamma ray bursts and exploding stars since its launch in 2004, tipping off other telescopes for more detailed observations.

Anxious to continue Swift's scanning of the universe, the space agency hired Katalyst Space last September for the $30 million salvage operation.