The mission patch for STS-98 -- Atlantis' voyage to deliver the Destiny module to the international space station. Photo: NASA

Engineers began inspections of electrical cable connectors in the solid rocket boosters of space shuttle Atlantis on Tuesday in the wake of a problem during the launch of sistership Endeavour two weeks ago.

Atlantis remains inside Kennedy Space Center's mammoth 52-story Vehicle Assembly Building (VAB) attached to its external fuel tank and twin solid rocket boosters atop a mobile launching platform. The shuttle has been slated for a 3.5-mile roll to launch pad 39A on Monday, but that six-hour trek is on hold while X-ray inspections of the connectors are performed.

NASA doesn't expect the shuttle to be cleared for rollout to the pad before the weekend. Despite the delay, the space agency still hasn't give up hope of launching Atlantis as scheduled on January 18 at 2:44 a.m. EST to deliver the U.S. scientific laboratory, Destiny, to the international space station.

The booster inspections were ordered because one of two explosive detonators in a strut connecting Endeavour's left-side solid-fuel booster failed to fire during launch November 30. The second detonator worked as planned and the booster separated safely.

"One of two pyrotechnic devices did not fire on the left-hand SRB on the lower strut," shuttle program chief Ron Dittemore explained Monday. "This is the first time we have seen this in the life of the program. Now, it's one of two, which means we were perfectly safe; you only need one of two to fire to separate properly.

"But what concerns us is we don't like going into a mission knowing that perhaps we have lost one leg of our redundancy."

Preliminary inspections on Endeavour's booster after it was plucked from the Atlantic Ocean indicate a broken wire may have been responsible for the failure and not a problem with the detonator itself. That's good news for NASA because replacing or inspecting detonators would have required taking Atlantis and its external tank off the two boosters to gain access.

NASA managers opted for a round of X-ray inspections of Atlantis' electrical cable connectors in the separation system wiring to be performed in the VAB where engineers have access to the hardware. The electrical connectors in question are located in both solid rocket boosters' external tank attachment (ETA) rings.

"What we're off looking at is trying to determine what caused the damage (in Endeavour's booster)," Dittemore said. "That's going to take a little bit of time to understand. And you need to really understand what the root cause is to define an plan of action to verify that we have good integrity on the vehicle that's in the VAB before it rolls out to the pad."

If Atlantis is not transported to the pad by early next week, NASA says the January 18 launch date would be delayed on a day-by-day basis.

Atlantis' 11-day mission will feature three spacewalks as the 32,000-pound Destiny module is attached to the growing international space station. Destiny is the centerpiece for U.S. scientific research aboard the orbiting outpost.