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
A shuttle mission to service the Hubble telescope will be delayed because of a malfunction on the observatory.
The glitch means Hubble cannot format or store data from its instruments, nor transmit the information to Earth.
The US space agency, Nasa, had planned to send the Atlantis orbiter to repair and upgrade the telescope next month.
Now, it says the shuttle is unlikely to fly until next year, to allow time for a replacement electronics box to be prepared for inclusion in the mission.
"Mid-February is looking to be a reasonable timeframe to do that," said Preston Burch, the Hubble manager at Nasa's Goddard Space Flight Center where telescope operations are overseen.
Nasa says the problem is in a box known as the Science Instrument Command and Data Handling (SIC&DH) Unit, and affects the functions carried out by its Science Data Formatter - Side A.
The glitch arose on Saturday and all attempts to correct have proved fruitless. The assessment is that the formatter has totally failed and will not be recoverable.
The anomaly prevents Hubble from formatting the data gathered by its instruments ready for sending to scientists on the ground. The malfunction also stops that data being stored locally on the telescope's solid state recorders for later transmission.
The back-up should allow Hubble to return to full operations
Hubble has a back-up - Side B - and if systems can be switched over, the observatory should return to normal operations. Engineers say it is a complex procedure but they hope to have Hubble functioning at its previous level of performance within a couple of weeks.
In the meantime, a spare SIC&DH Unit on the ground will be prepared for flight, to be included as an additional servicing task on the forthcoming Atlantis mission.
Ed Weiler, Nasa's associate administrator for science, said it was important Hubble had redundancy for Side B going into the future
"If we just go to Side B, we would be left with a system that had several single point failures, and that would be a risk to the [Hubble] mission for the long duration," he explained.
"By going ahead and accepting a delay of perhaps several months, we can get our full-up spare tested and ready to go - and if we could put that in [Hubble] sometime in the winter, we would have an observatory that was again doubly redundant; that is, it would have back-up systems."
The 62kg (136lb) box requires no new tools be developed for astronauts to fit it inside Hubble. However, time will have to be found in an already tight spacewalk schedule to get the job done.
Setting a new date for the mission is complicated by Nasa's strict flight rules introduced after the Columbia disaster.
Because Atlantis cannot get to the safety of the space station from Hubble's orbit if something goes wrong, a second shuttle must be put on the launch pad ready to fly a rescue mission if required.
For the planned 14 October launch opportunity, the back-up was supposed to be the Endeavour orbiter. But this ship is also needed for a space station mission on 16 November.
The Atlantis delay means Endeavour's mission may now be brought forward by a couple of days, and Atlantis slotted into the shuttle manifest in February or April next year when another orbiter would take up the rescue-readiness role.
Flight rules require two shuttles are prepared for a Hubble mission
The upcoming mission to Hubble is the fifth and final flight designed to keep the great observatory serviceable.
Hubble's batteries and gyroscopes, which are used to point the telescope, are degrading and they now need to be replaced.
The shuttle crew is also tasked with installing 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.
The Atlantis astronauts must also repair two instruments that have failed in recent years - the Advanced Camera for Surveys (ACS) and the Space Telescope Imaging Spectrograph (STIS).
If the work is carried out successfully, it should allow Hubble to keep operating into the next decade.
Ed Weiler said everyone should think it was lucky that the Data Formatter broke just before Atlantis set off on its servicing mission rather than just after it.
"Hubble has a habit of coming back from adversity; and the Hubble team works miracles," he added.
"I'm not too concerned about this. We'll find a way to get this fixed. This particular failure was anticipated and we have spare hardware ready to go."
SERVICING THE HUBBLE SPACE TELESCOPE
Shuttle Atlantis will grab Hubble with a robotic arm and pull it on to a work platform to allow astronauts easy access to its interior
Hubble has six gyroscopes that are critical to its control and pointing systems. These have started to fail and all will have to be replaced
Six new batteries will rejuvenate the electrical system; astronauts will attach new thermal blankets to insulate sensitive components
The telescope has two instrument bays; the COS and WFC3 will be slid into racks made vacant by the removal of older instruments
An attempt will also be made to repair the Space Telescope Imaging Spectrograph (STIS) which stopped working in 2004