Next month's space shuttle mission to service the Hubble Space Telescope experienced a "significant anomaly", according to NASA. Saturday night, Side A of Hubble's Science Data Formatter failed, preventing the transfer of all science data to the ground. The telescope's main computer places the payload computer and science instruments into safe mode as a result of the failure. The failure has forced an indefinite delay in the launch of Atlantis.The malfunctioning system is Hubble's Control Unit/Science Data Formatter - Side A. Shortly after 8 p.m. on Saturday, Sept. 27, the telescope's spacecraft computer issued commands to safe the payload computer and science instruments when errors were detected within the Science Data Formatter. An attempt to reset the formatter and obtain a dump of the payload computer's memory was unsuccessful.Additional testing demonstrates Side A no longer supports the transfer of science data to the ground. A transition to the redundant Side B should restore full functionality to the science instruments and operations.The transition to Side B operations is complex. It requires that five other modules used in managing data also be switched to their B-side systems. The B-sides of these modules last were activated during ground tests in the late 1980s and/or early 1990, prior to launch.The Hubble operations team has begun work on the Side B transition and believes it will be ready to reconfigure Hubble later this week. The transition will happen after the team completes a readiness review.Hubble could return to science operations in the immediate future if the reconfiguration is successful. Even so, the agency is investigating the possibility of flying a back-up replacement system, which could be installed during the servicing mission.