NASA has confirmed it will be unable to launch the Hubble Space Telescope fourth and final servicing mission until May and then only if a spare command and data handling unit's "significant anomaly" is resolved in the next fortnight.

NASA Goddard Space Flight Center Hubble manager Preston Burch says that if the anomaly can be identified and fixed by late November the unit could restart testing and go to Kennedy Space Center in April.

The command and data handling unit uses an "A side" that has a B side for back-up. In testing the A side has worked intermittently. The unit's problems are not a new issue. Burch says that in the early 1990s a spare unit failed testing.

Failure of the A side on the Hubble's unit on 27 September scuppered the servicing mission's scheduled 10 October launch. That mission would have seen Space Shuttle Atlantis's crew change, upgrade and repair several instruments. NASA subsequently predicted a February launch. Since September most of Hubble's capabilities have been restored, but the servicing mission will now include a replacement command and data handling unit.

On 23 December the US Congress will receive a report recommending that the National Transportation Safety Board legally become the lead investigator for commercial human spaceflight vehicle accidents.

Source: Flight International