NASA is once again trying to reboot the Hubble Space Telescope, agency officials said Thursday.

The telescope’s instruments have been shut down since the end of September, when a router that formats science data for transmission to the ground suffered an electrical failure.

Last week, the telescope’s managers succeeded in turning the router back on, using a backup electrical and data channel that had not been used in the 18-year life of the telescope. A pair of electrical anomalies, however, sent the telescope back into “safe mode.”

One of the anomalies, an incorrect voltage in Hubble’s Advanced Camera for Surveys, was the result of a timing problem between a pair of software routines in the camera and has been corrected, said Art Whipple, an engineer at the Goddard Space Flight Center in Greenbelt, Md.

The second anomaly was apparently a temporary short circuit or some other ghost electrical signal that caused the telescope’s payload computer and the router to reset themselves. The payload computer handles Hubble’s scientific data and commands the instruments. There was apparently no lasting harm and no fuses were blown.