The launch of Europe’s Metop-A polar-orbiting weather satellite likely will be delayed until early September to give Russian Soyuz rocket launch teams time to resolve the issues that stopped the July 19 launch attempt three minutes before liftoff, the chief of executive of the French-Russian joint venture that markets the Soyuz rocket said July 21.

Starsem S.A. Chief Executive Jean-Yves Le Gall, who is also chief executive of the Arianespace commercial-launch consortium, said the July 19 launch cancellation — the third in three days — was caused when the Soyuz ground system showed an error reading for the purge lines that connect to the rocket’s fuel tanks.

Whether the error reading accurately reflected a problem remains unclear, Le Gall said.

“After the July 19 launch attempt, we debated whether a July 20 launch was feasible. When I could not get a clear answer on what happened, I asked that the launch campaign be suspended to give everyone time to assess the issues and correct the problem. The rocket has now been returned to its assembly building, and Metop-A has been returned to the clean room and made safe for storage. My best guess is that we will be able to launch Metop-A in early September. The problems we had on this launch had to do with the ground installations around the vehicle, not the Soyuz rocket itself, so there is no reason to expect a delay longer than that.”

Russia’s Soyuz rocket, in its Soyuz and Molnya configurations, has conducted 1,711 launches, the most recent being the July 21 launch of a Russian military observation satellite from the Plesetsk Cosmodrome in northern Russia.

The Soyuz rocket version used for Metop-A, called the Soyuz 2-1a, employs a new digital control system and a new inertial measurement unit that have been used only once — in a November 2004 launch from Plesetsk. The Metop-A launch is the first time this new control and navigation system has been used at Russia’s Baikonur Cosmodrome in Kazakhstan.

Le Gall conceded that the new design is probably one reason for the three launch aborts for Metop-A. The first attempt July 17 was cancel ed about 90 minutes before launch when ground teams saw what appeared to be a defective reading on one of the Soyuz rocket’s gyroscopes, part of the inertial navigation system. It turned out that the gyroscope was fine and that ground teams had introduced incorrect data into its programming, resulting in the error signal.

The launch was rescheduled for July 18. But instead of completely emptying the rocket’s liquid oxygen/kerosene fuel tanks after the July 17 launch scrub, Soyuz rocket preparation teams left them partially filled because of a shortage of liquid oxygen at the Baikonur site, Le Gall said.

When refueling began July 18, the ground system reported an error because it had been programmed to expect the launch-preparation sequence to start with empty tanks. By the time they determined the problem’s cause, the Metop-A launch window for July 18 had passed.

The Metop-A launch window occurs once each day and lasts only a few seconds. Eumetsat and European Space Agency (ESA) Metop program and flight-control officials had been given conflicting information about how many consecutive launch attempts could be made before the Soyuz would need to be returned to its assembly building to replace hardware that is stressed from repeated filling and emptying of fuel tanks.

Starsem Vice President Francois Maroquene said Soyuz, which has the longest operational history of any launch vehicle currently in use, has rarely, if ever, faced a situation of three straight launch aborts. But he said his understanding is that after three attempts, certain components would need to be replaced, a procedure that would take at least several days, depending on what hardware is available at the Baikonur site.

Jean-Pierre Cau, head of the Metop program at the satellite’s prime contractor, Astrium Satellites, said Metop-A would be able to remain as is for an extended period of time and should not need any special maintenance between now and the next launch attempt.