Hubble re-boot expected this week

HUBBLE SPACE TELESCOPE Named after the great US astronomer Edwin Hubble Launched in 1990 into a 600km-high circular orbit Equipped with a 2.4m primary mirror and five instruments Length: 15.9m; diameter: 4.2m; Mass: 11,110kg

US space agency (Nasa) officials say the orbiting Hubble telescope should come back online for full science operations on Friday.

The telescope suffered a glitch two weeks ago in a key electronics box that prevented it from routing data from its instruments to the ground.

Engineers will begin the process of switching Hubble over to a back-up system on Wednesday.

The officials told reporters they were confident the procedure would work.

"We expect the first data to flow all the way from one science instrument to the ground Thursday night, and then we expect the full flow of science to resume Friday morning," said Art Whipple, the manager of the Hubble Space Telescope Systems Management Office at Nasa's Goddard Space Flight Center.

Hubble's main flight computer put instruments in a protective safe mode on Saturday, 27 September, when it detected a problem in the observatory's Science Instrument Command and Data Handling (SIC&DH) Unit.

The anomaly was traced to a box that formats, stores and routes data gathered by Hubble's imaging instruments.

Over the past fortnight, engineers have been working through the details of a fix that involves switching the observatory over to a "B" formatter.

It is a complex procedure but it should return Hubble to normal operations.

"It's probably not unlike what an IT professional might do with an office network," said Mr Whipple.

"The difference is that on the ground you power things on and off and reconfigure by pushing buttons and swapping cables. We can't do that, of course, in space."

Instead, a long series of commands must be sent up to Hubble to make it adopt the new configuration.

The failed box will be replaced by astronauts when they next service Hubble.

That mission should have launched this month but the glitch means it will not now take place until next year.

Engineers on the ground need time to test the replacement and the astronauts will require some extra training.