Space shuttle Discovery has returned to the Vehicle Assembly
Building (VAB) from the launch pad at NASA's Kennedy Space
Center in Florida to finish external fuel tank testing, the US
space agency says. The manoeuvre, known as a "rollback," began
on the night of 21 December, taking six hours to make it down
the 5.47km (3.4mi) track from launch pad 39A back to the VAB.
The move was delayed by a day due to problems with the levelling
system on the crawler-transporter that moves the shuttle to and
from the launch pad. In the VAB, technicians are using x-ray
scans to see beneath the foam insulation on all 108 support
beams, called stringers, on Discovery's external tank. The team
will also remove the 89 strain gauges and temperature sensors
still attached to the tank from the 17 December tanking test and
reapply foam to those areas. Shuttle programme managers are
keeping options open to modify some of the stringers, depending
on the results from the additional testing. Managers are
expected to decide on 30 Decembe