An Asian telecommunications spacecraft was deployed in the wrong orbit by its sea-launched rocket early Tuesday, but the satellite's maker is confident that the altitude shortfall can be overcome without jeopardizing the mission.

As seen from the control ship positioned a short distance from the launch platform, the Zenit rocket lifts off with Telstar 18. Credit: Sea Launch

A Sea Launch Zenit 3SL rocket blasted off from its floating platform in the Pacific Ocean at 0359 GMT (11:59 p.m. EDT). The rocket's lower two stages, which are Ukrainian-made, fired during the first nine minutes of flight. The Russian-built Block DM-SL upper stage then performed an initial burn to reach a parking orbit around Earth.

After a 36-minute coast, the Block DM-SL reignited for what was supposed to be a six-minute firing to reach an elliptical geosynchronous transfer orbit stretching from 35,768 km at its high point to 760 km at its lowest point.

About 65 minutes after liftoff, the 10,229-pound Telstar 18 satellite was released from the rocket as Sea Launch hailed the deployment mission a success.

But a few hours later, Sea Launch acknowledged the orbit achieved was lower than planned. Russian media reports indicated the orbit's high point was only 21,000 km.

"We are still assessing the data and we are optimistic the spacecraft will achieve its specified lifespan on orbit. We are supporting our Loral customer in this assessment. We will issue additional information as it becomes available," Jim Maser, president and general manager of Sea Launch, said in a written statement.

Engineers are investigating what caused the launch problem. The Block DM motor has failed several times in recent years while serving as the upper stage on Russian Proton rockets.

The Zenit rocket lifts off from the Odyssey launch platform. Credit: Sea Launch

As controllers established contact with Telstar 18, engineers were working to determine if the satellite had enough onboard fuel to boost itself into the correct orbit while still having a propellant reserve to fulfill its intended life expectancy.

By midday Tuesday, the satellite's builder released a statement saying Telstar 18 would overcome the launch problem.

"According to Sea Launch, the spacecraft separated from the rocket's upper stage prematurely and was placed into a lower than expected transfer orbit," Loral Space and Communications said.

"However, current data indicates the satellite has sufficient onboard fuel to bring it to its final orbital position and exceed its 13-year specified life.

"Telstar 18 has deployed its solar arrays and all systems on the spacecraft are operating normally."

As with most communications satellite launches, a rocket carries its payload into an egg-shaped geosynchronous transfer orbit. The satellite then uses its engine to raise the orbit's low point and circularize the orbit at 36,000 km. From that high altitude, the satellite matches Earth's rotation and appears parked over one spot of the globe.

In the case of Telstar 18, the satellite must now use its precious fuel to compensate for the launch shortfall and then reach geostationary orbit. What's more, enough fuel must be saved for the craft to keep itself properly positioned over the course of its life.

Built by Space Systems/Loral in Palo Alto, California, the satellite will be operated by Loral Skynet to provide television broadcasting, Internet services and other telecommunications across the Asia-Pacific region.

An artist's concept of Telstar 18. Credit: Loral

APT Satellite Company Limited of Hong Kong provided a portion of funded for this spacecraft. The deal gives the company use of 68.5 percent of Telstar 18's capacity. The number of transponders used by APT will be reduced over time, ultimately to 54 percent of the satellite's capacity, officials said.

APT needs the satellite to replace the aging Apstar 1 spacecraft launched 10 years ago.

Telstar 18 features 38 C-band and 16 Ku-band transponders. The C-band coverage zone includes a broad area of China, southeast Asia, Australia, New Zealand, the Pacific islands and Hawaii. The Ku-band footprint reaches China, India, Taiwan, Hong Kong and Korea.

Sea Launch had planned to carry the Intelsat Americas 8 satellite (formerly known as Telstar 8) into space later this summer. How Tuesday's incident will impact those plans remains unclear.

Tuesday's flight was the 14th Sea Launch mission since 1999. One previous mission failed -- in 2000 -- when the second stage malfunctioned, causing the rocket and its ICO mobile communications satellite to fall into the Pacific.

Earlier this year, the Loral-built Estrela do Sul communications satellite failed to deploy one of its two power-generating solar arrays after riding a Sea Launch rocket into orbit. Officials never announced what caused that problem.