Listen Live: 12:30 p.m. Hubble Telecon

NASA aims to restart Hubble Space Telescope astronomy this week and officials are being briefed at this hour on a plan to turn on a back-up instrument control and data formatter that hasn't been used or tested since the observatory was launched in 1990.

A go-ahead to begin the complicated switchover is expected at the end of the meeting and you can listen in to a 12:30 p.m. media teleconference on the matter by clicking here: Hubble Telecon.

The telescope's prime instrument control and data formatting unit failed late last month, forcing ground controllers to shut down astronomical observations of planets, stars and galaxies across the universe.

The failure also forced NASA to delay until at least February the planned launch today of Atlantis and seven astronauts on a fifth and final Hubble servicing mission. The failed unit is considered so important that NASA officials decided to delay the mission until a spare can be readied for flight.

The complicated switchover is considered critical. If it doesn't work, the flagship of NASA's fleet of orbital observatories will remain out of commission until the Atlantis astronauts can install the spare on one of five spacewalks planned for the STS-125 Hubble servicing mission.

Engineers are taking a cautious approach to the operation. The complexity of it is unrivaled because ground controllers also have to rev up the backups for five other key electrical components in order to operate the backup instrument control and data formatting unit.

NASA officials nonetheless have high confidence that the 40-hour operation -- which tentatively is set to Wednesday -- will be successfully completed. In that case, stalled science operations would get back under way as early as Friday.

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.

NOTE ON IMAGES: Click to enlarge and save the Hubble Space Telescope images captured during a 1999 servicing mission flown aboard Discovery. You can also click the enlarged images to get even bigger views. Photo credits: NASA/STS-103 Crew. The line art comes the Hubble Systems primer.