The Hubble Space Telescope (HST) was placed in a safe mode on 13 November after its gyroscope No 1 stopped operating, leaving just two operational units. Observations have been suspended. The situation, which had been anticipated, adds extra drama to the forthcoming STS103 Discovery mission to conduct the third service for the Hubble and replace all its six gyros.

The Space Shuttle Discovery is on launch pad 39B at the Kennedy Space Center following its roll-out on 13 November, to be prepared for its launch on 6 December.

This servicing mission has been brought forward from next June because of concerns over several gyro failures. The mission will take place in two parts, one to be launched on 6 December and the other in mid-2001.

The Discovery's mission, called 3A, will replace the gyros, and install a fine guidance sensor, a transmitter, a spare solid state recorder, a new computer and a high voltage/temperature kit for protecting batteries from overheating. The crew will also begin repairs to insulation blankets.

The 3B mission in 2001 - probably flying the same crew - will continue those repairs, replace the telescope's solar arrays with ones that provide 30% more power, add cooling units to the infrared camera and multi-object spectrograph, and fit a new camera 10 times more powerful than the Hubble's present Faint Object Camera. The HST may be able to operate until 2010, but a fourth servicing mission, due in 2003, will be the last.

Source: Flight International