Hubble flight slips by 4-5 weeks

The date of the shuttle mission to repair and upgrade the Hubble Space Telescope should be confirmed in the next few weeks, Nasa says.

The flight is currently set for 28 August but the US space agency admits this will slip by four to five weeks.

Getting a new class of external fuel tank ready for the Atlantis orbiter's launch has taken longer than expected, Nasa explained.

The servicing mission should extend Hubble's lifetime to at least 2013.

"Right now Hubble is scheduled for August 28. We really cannot make that date with the external tank processing schedule," said the agency's space shuttle programme manager, John Shannon.

"This all falls from the processing changes that were made to assemble the tanks with the post-Columbia [modifications] in-line.

"What we're looking at is a four-to-five week slip in the Hubble date; sometime in late September, early October," he told a media briefing at the Johnson Space Center on Thursday.

Nasa is about to introduce the first so-called "in-line" external tank on this month's Discovery flight.

The tank has been built from the ground up with the upgrades demanded after the Columbia disaster, which saw the loss of seven astronauts on re-entry to the Earth's atmosphere in 2003.

The upgrades are designed to minimise the shedding of insulation foam - the problem that doomed Columbia.

'Better vision'

Prior to this month's flight of Discovery to the International Space Station, the upgrades had been retrofitted on to pre-built tanks.

Engineers have had to get used to the new in-line assembly procedures and this has had a knock-on effect for Nasa's tight launch manifest.

Because Atlantis cannot get from Hubble's orbit to the "safe haven" of the ISS if it gets into trouble, Nasa managers have ordered that the Endeavour shuttle must be ready on the pad to mount an astronaut rescue if required.

And with five flights to the station already booked for 2008, there was little room for manoeuvre if technical issues intervened.

The slippage means the last shuttle mission of the year will now probably be moved to early 2009.

However, John Shannon said this would not change the retirement date of the shuttle fleet, expected in about June 2010.

The final servicing of Hubble was originally cancelled following the Columbia disaster, but was then re-instated in the shuttle launch manifest after a concerted campaign from astronomers who were unhappy at the prospect of losing a telescope that has made so many remarkable discoveries.

Without servicing, the observatory is not likely to last more than a couple of years.

Its batteries and gyroscopes, which are used for pointing, are degrading and have to be replaced.

The servicing mission will also see the installation of two new instruments: the Wide Field Camera 3 (WFC3), and the Cosmic Origins Spectrograph (COS). The new instruments will improve significantly Hubble's ability to probe distant, faint objects in the early Universe.

Discovery's mission to the ISS on 31 May will deliver the main segment of the Japanese Kibo science laboratory.

RELATED INTERNET LINKS
HST Servicing Mission 4 (Nasa)
Hubble Space Telescope (Nasa)
Hubble Space Telescope (Esa)
HubbleSite
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