Ground controllers have stopped a thruster fuel leak aboard an on-orbit Boeing 601-model satellite owned by JSat Corp. of Tokyo, fixing a problem that had threatened the Japanese firm with a total and uninsured loss on the spacecraft, according to Boeing officials.

The JCSat-1b communications satellite will be returned to service, Boeing said.

The thruster problem occurred in July and followed a similar, but short-lived, problem in January. Officials from JSat have been forced to move a spare satellite into position to pick up the traffic on the stricken satellite.

With its one in-orbit spare in use at the company’s 150 degrees east longitude slot, JSat was under pressure to accelerate a planned satellite-replacement program and has ordered a JCSat-11 spacecraft from Lockheed Martin Commercial Space Systems. The contract, announced by Lockheed Martin Oct. 3, marks the third consecutive satellite that Japan’s biggest satellite operator has ordered from the Newtown, Pa.-based manufacturer .

Like the JCSat-9 and JCSat-10 satellites on order, the JCSat-11 will use Lockheed Martin’s A2100 AX satellite frame. It is expected to be delivered in 2007 and will serve as an in-orbit backup for the JSat fleet.

In response to Space News questions, JSAT spokesman Hideyuki Torii said Oct. 5 that JCSat-9 will be launched within the next six months. JCSat-10 is expected to be launched before March 2006, with JCSat-11 following in 2007.

Torii said JSat had not yet completed its review of the status of JCSat-1b, whose in-orbit insurance coverage does not currently cover losses related to the thruster. It is common in the space insurance industry for underwriters to exclude certain components when signing up to cover satellite in-orbit policies, which are renewed every year .

Torii said the JCSat-R satellite, which has been moved into position to replace the defective JCSat-1b, is fully insured.

Marta E. Newhart, a spokeswoman for Boeing Satellite Systems International of El Segundo, Calif., said Oct. 6 that the JCSat-1b thruster leak is unique to this satellite and is not a serial defect that has affected other Boeing 601-model satellites.

” In July, JCSat-5 [the name of the satellite before it was renamed JCSat-1b in orbit] experienced an anomaly which caused the spacecraft’s attitude to tilt, or create an off-pointing of the satellite’s normal on-orbit angle,” Newhart said in a written statement. “The anomaly was isolated to a leak in the thruster valve of the spacecraft propulsion system. This leak has been stopped and testing continues to be conducted. The anomaly has not occurred on other Boeing satellites and at this time we have no new information that would indicate this anomaly will impact other Boeing satellites.”

JSat’s nine-satellite in-orbit fleet includes six Boeing 601-model satellites. Four of them — JCSat-3, JCSat-R, JCSat-4a and JCSat-1b — were launched between 1995 and 1999. During this period, the Boeing 601 satellite was the world’s best-selling model.

The 601 has since become a case study for serial defects in satellites. More than $1 billion in insurance claims have been paid to cover in-orbit losses. Boeing became the owner of the 601 production line following its October 2000 purchase of the business from Hughes Electronics.

Torii declined to say whether JSat’s purchase of a new satellite is directly related to the trouble on JCSat-1b. But the order will add to JSat’s capital expenditures at a time when the company’s financial performance is suffering. In its annual report to shareholders, JSat cited capital expenditures as one reason for the company’s poor performance in 2004.

In addition to the two other Lockheed Martin satellites on order, JSat has agreed to pay almost all of the $140 million capital expense of the Horizons-2 satellite that will be co-owned with PanAmSat Corp. of Wilton, Conn. It is a PanAmSat-registered orbital slot that will be used for the Horizons-2 business. PanAmSat will reimburse JSat for its 50-percent share of the total investment in the Horizons-2 venture over several years.

For its 2004 financial year, which ended March 31, 2005, JSat reported sales of 42.88 billion yen ($378 million), a 7.3-percent decline in yen terms over the previous year. Net profit, at 4.5 billion yen, was down 26 percent.

EBITDA, or earnings before interest, taxes, depreciation and amortization — a commonly used financial metric among satellite operators — was 56.8 percent of revenues, down from 61.6 percent in 2004.

In its annual report issued Aug. 22, JSat blamed “up-front expenditures aimed at future growth, and a harsh business environment, chiefly in the domestic communications sector” for its performance in 2004. “The business environment has become severe.”

JSat said it expects revenue to decline again in 2005.

Peter B. de Selding was the Paris bureau chief for SpaceNews.