Hubble telescope runs into more trouble

NASA's bid to bring the Hubble Space Telescope out of a scientific slumber has come to a halt while engineers try to sort out trouble encountered during an operation aimed at switching to a critical back-up control unit.

Forty to 50 engineers have been working round-the-clock since early Wednesday to turn on a back-up instrument control and data formatting unit that has never be used in the 18 years the observatory has been in orbit.

The telescope's prime unit failed Sept. 27, prompting Hubble to automatically shut down almost all science observations. NASA then decided to delay the planned launch Tuesday of a fifth and final Hubble Space Telescope servicing mission until a spare unit could be certified for flight and shipped to Kennedy Space Center for launch aboard shuttle Atlantis. That mission now is being targeted for launch in February.

Hubble project engineers ran in to trouble when commands were being sent to resuscitate one of the telescope's main science instruments. The plan had been to have all telescope instruments up and operating today.

Unclear right now is how serious the trouble might be. In a worst case scenario, it appears, the telescope would be unable to perform most science observations until astronauts could service the observatory. Hubble probably still could perform astrometry -- the science of determine the precise position of celestial objects -- with its Fine Guidance Sensor. The FGS uses different means to format and beam data back to Earth.

The switchover to the back-up unit is considered complicated because five other back-up electronics units also have to be turned on in the process, which involves sending thousands of commands to the observatory.

Engineers are meeting to determine a course of action. A media telecon likely will be held later this afternoon.

Hubble is equipped with prime and backup Control Unit/Science Data Formatters, electronics boxes that compose and send all commands and data to destinations such as the telescope's flight computer and its data management unit.

A primer on Hubble systems is here: HSTSYSTEMS. See Section 5.5 for details on the Control Unit/Science Data Formatter.

More to come.

IMAGE NOTE: Click to enlarge and save the awesome photo of the Hubble Space Telescope. It was taken by the crew of the STS-103 mission in December 1999.