At the time of the called scrub, managers and Shuttle engineers were also discussing a problem with the second of two Master Events Controllers (MEC) on Endeavour. The MECs control the orbiter's pyrotechnic devices and process the signals that separate the Solid Rocket Boosters and the External Tank. During today's launch attempt, the No. 2 MEC that is located in the orbiter's aft engine compartment, failed a standard test procedure just prior to entering the T-20 minute hold. Managers opted to extend the hold at T-20 minutes to allow engineers an opportunity to evaluate the health of the MEC.

Following the weather scrub, managers elected to set up a team of engineers who will meet throughout the evening tonight to better understand why the MEC failed its initial test, but subsequently passed an additional test. Further tests of the MEC will be conducted tonight as managers prepare for a meeting early tomorrow morning at which time a decision whether or not fly is expected to be made.

Pending a decision to proceed with a launch attempt tomorrow, loading the External Tank with the cryogenic propellants will begin at about 4 a.m.

Shuttle weather forecasters indicate a 60 percent chance of favorable weather on Tuesday. The forecast calls for the cold front that passed through today to be near the Florida Straits tomorrow. A surface high is expected to build and we should see a gradual decrease in the cloud cover. Throughout the launch window the following conditions can be expected: clouds scattered to broken at 3,000 feet, and broken at 10,000 and 25,000 feet; visibility at 7 miles; winds from the northwest at 10 peaking to 15 knots; temperature 59 degrees F; relative humidity 57 percent; dewpoint 44 degrees F; and the chance of rain showers and low, thick clouds.