Controllers at NASA's Goddard Space Flight Center are calibrating the Hubble Space Telescope's instruments to begin making observations again Friday, after switching the orbiting observatory's Science Instrument Control and Data Handling system to its backup "B" side.

The calibration involves comparing baseline exposures on the Advanced Camera for Surveys (ACS), Wide Field Planetary Camera 2 (WFPC-2) and other instruments that have been handled by the newly activated B side with the same exposures supported earlier by the "A" side, which failed Sept. 27 and sent the telescope into safe mode (Aerospace DAILY, Sept. 30).

If all goes as planned, "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," the Hubble program said this morning.

The changeover to the redundant hardware followed extensive tests of the complex commanding procedures using Goddard's Vehicle Electrical System Test (VEST) facility, and a review and approval of the procedures by top NASA engineers and managers. Completion of the changeover will allow Goddard engineers to begin using the VEST to prepare a spare data-handling system for delivery to the telescope in orbit on the final Hubble servicing mission next year.

The servicing mission on the space shuttle Atlantis was postponed from Oct. 16 after the primary data-handling system failed following 18 years of operation. The replacement unit must be flight qualified before it can be installed in the telescope by spacewalkers to restore redundancy for the new instruments and other upgrades to be delivered by Atlantis (Aerospace DAILY, Oct. 13).

Photo: NASA