Updated NASA is cautiously optimistic that Hubble will soon be back in action following a boot-up of the space telescope's venerable 486 back-up system.

Hubble was last month blinded by the failure of the Control Unit/Science Data Formatter (CU/SDF) in its operational Side A Science Instrument Command and Data Handling unit (SIC&DH), which packets data from the 'scope's five main instruments for transmission back to Earth. NASA decided to switch operations to the redundant Side B of the SIC&DH, which hadn't been fired up since an upgrade to the main computer (details here (pdf)) back in 1999 empowered Hubble with a mighty Intel 80486 microchip.*

NASA explained earlier this week: "The Hubble team will reconfigure Hubble to use the redundant SDF in the SIC&DH, and six redundant associated components in the spacecraft data management systems (DMS), to restore science operations. Five of the six redundant components in the DMS that will be brought on-line also have not been powered since 1990."

The agency reported yesterday: "The team completed switching the required hardware modules to their B-sides this morning and received telemetry that verified they had good data. Everything at this point looks good. The 486 computer on Hubble was reloaded with data around noon and successfully performed a data dump back to the ground to verify all the loads were proper. This afternoon the team brought Hubble out of safe mode and placed the 486 computer back in control."

NASA was due to "reconfigure Side B of the SIC&DH computer" late yesterday, after which Hubble would "begin executing a pre-science command load, which involves sending normal commands to control the spacecraft and resume communications satellite tracking with the HST high gain antennas".

Art Whipple, manager of the Hubble Space Telescope Systems Management Office, explained that Hubble should return the first science data today and be "back in its science mode on Friday morning". ®

Update

NASA explained yesterday that overnight on the 15-16 October, "the Advanced Camera for Surveys (ACS), Wide Field Planetary Camera 2 (WFPC2) and Near Infrared Camera and Multi-Object Spectrometer (NICMOS) instruments were retrieved from safe mode to establish that each has a working interface to the Side B SIC&DH".

Engineers then intended to last night "recover Hubble’s science instruments from their safe modes" and carry our "internal exposures and calibrations of the telescope’s science instruments".

The agency elaborates: "Scientists ... should complete their review of the internal exposures by noon on Friday, October 17. This procedure involves collecting and comparing baseline exposures previously supported by Side A of the SI C&DH to new exposures supported by Side B. This review will be one last check of the 'transparency' (non-impact) of switching to the redundant spacecraft electronics the Hubble team activated on Wednesday."

It concludes: "A full schedule of science observations with the WFPC2 camera, ACS’ Solar Blind Channel camera, and the Fine Guidance Sensors will resume early Friday morning."

Bootnote

*Thanks to those readers who clarified just how long Hubble has been packing a 486.