The Sea Launch Zenit 3SL rocket is moments away from liftoff on Sunday at 1449 GMT (9:49 a.m. EST). Photo: Sea Launch

Sea Launch said Wednesday that a problem with the Zenit 3SL rocket's second stage doomed its commercial mission on Sunday, correcting an erroneous statement made shortly after the failure.

The three-stage rocket blasted off from a floating platform stationed on the equator in the Pacific Ocean. Contact with the booster was lost minutes later as the Zenit and its ICO mobile communications satellite went off course and crashed back to Earth.

About two hours after the incident, Sea Launch president Wilbur Trafton announced the failure and said, "During the third stage burn, we got what we think was some indication of an off-nominal trajectory for the spacecraft."

A Sea Launch spokeswoman corrected the statement on Wednesday, saying Trafton meant to say "second stage."

The difference is crucial to rival International Launch Services, which markets U.S. Atlas and Russian Proton rocket. The Sea Launch Zenit's third stage and the upper stage for Proton is the same Russian-made Block DM motor.

Sunday's failure occurred before the second stage could separate from the Block DM-SL booster. The upper stage would have propelled the attached ICO satellite into its planned orbit about 6,500 miles above Earth.

Read our earlier story for a complete summary of Sunday's events.

Meanwhile, Ukraine's Yuzhnoye/Yuzhmash -- which builds the Zenit's first and second stages -- is making progress in uncovering clues to what went wrong during the third Sea Launch flight. The two earlier launches last year were successful.

The first Sea Launch Zenit 3SL rocket during tests last year. Photo: Sea Launch

Officials say the rocket failed to gain enough velocity to achieve orbit although it reached an altitude of about 100 miles.

Sensing the rocket was not functioning properly, an onboard safety system shut down the second stage's main engine about 7 1/2 minutes into flight, sending the rocket plummeting back to Earth. Impact with the South Pacific occurred about 2,700 miles southeast of the launch site.

News reports on Wednesday claimed a computer error shortly before liftoff allowed a pressure valve on the second stage to remain open during launch. That caused the stage's vernier steering system to not work properly. Reports circulating in the aerospace community suggested two of the rocket's four vernier jets had not ignited.

Sea Launch officials would not comment on the reports, however.

Zenit rockets are known as highly automated vehicles with most of the countdown procedures controlled by computer sequence. There have been 36 Zenit launches since 1985 and 9 have failed.

Sea Launch has named its chief engineer, Jim Maser, to lead the Failure Oversight Review Board.

The board will begin its work once the U.S. government approves a Technical Assistance Agreement to allow Sea Launch partners Boeing, Yuzhnoye/Yuzhmash and Russia's Energia to share information. Currently, the different aerospace companies are reviewing their own data.

Destroyed in Sunday's botched launch was the first spacecraft for ICO Global Communications' constellation of cellular telephone and data relay satellites. The London-based consortium planned to launch a dozen of the Hughes-built craft but only needs 10 to offers its worldwide service. The other two would act as spares.

After the mishap, Sea Launch team members aboard the vessels in the Pacific gave this message: "Sea Launch has lost its smile for a day, but not its hope, dream or determination. We shall withstand the fate's harsh blow. We shall bounce back with the resilience of the undaunted will. Sea Launch is tough! Equator, we shall see you soon!"