PARIS — Honeywell Aerospace has isolated the cause of a suspected defect in its reaction-wheel assemblies that has delayed the launch of two satellites, and has proposed to customers a straightforward fix, a Honeywell official said July 22.

Dave Douglass, vice president of space, missiles and munitions at Phoenix-based Honeywell Aerospace, said the defect is a contaminant in a shipment of specialty grease supplied to Honeywell for use with ball bearings that are part of the reaction-wheel assembly systems.

In an interview, Douglass said the company has determined how and when the contaminant entered the specific grease shipment from one of its suppliers. Honeywell sent written notice to satellite customers affected by that shipment in mid-June and said it had begun testing the grease to determine whether it was flight-worthy despite the fact that the contaminant had not been certified for use in orbit.

The tests of the suspect grease were to take several weeks.

The Japan Aerospace Exploration Agency elected to replace the suspect component aboard its Quasi-Zenith Satellite, named Michibiki, that had been scheduled for an Aug. 2 launch aboard a Japanese H-2A rocket. The satellite, in development for years, is designed to provide positioning, timing and navigation service to Japan and the surrounding region as a complement to the U.S. GPS satellite constellation.

Honeywell had one other customer that had taken delivery of reaction-wheel assemblies with the contaminated grease whose satellite was scheduled for imminent departure: Boeing Space and Intelligence Systems of Seal Beach, Calif.

The Boeing-built SkyTerra 1 L-band mobile communications satellite, whose development delays had already forced Reston, Va.-based SkyTerra Communications Inc. to seek a launch deadline extension from U.S. regulators, was in final preparation for shipment when the Honeywell letter arrived, according to Honeywell and SkyTerra. SkyTerra’s name was changed to LightSquared July 19.

Douglass said that with SkyTerra 1, the only satellite with the suspect grease whose launch date was fast approaching, Honeywell focused its attention on testing the contaminated grease.

“Boeing was anxious to receive a determination from Honeywell” about whether the reaction-wheel unit could be flown as is, Douglass said. “We looked at the duty cycle for the SkyTerra application and recommended to Boeing that the units we had shipped were acceptable. We delivered that assessment on July 9.”

Boeing had been scheduled to ship SkyTerra 1 on or about July 16 for a planned mid-August launch aboard an International Launch Services Proton rocket from the Russian-run Baikonur Cosmodrome in Kazakhstan.

Several days before the scheduled shipment, Boeing informed SkyTerra/LightSquared that the satellite would be delayed. Boeing declined to specify the reasons for the delay, and specifically declined to say whether it was related only to the reaction-wheel assembly or involved other satellite components or non-satellite-related matters involving SkyTerra financing.

Boeing has provided substantial vendor financing to LightSquared, a company that was in a precarious financial situation before it was purchased by hedge fund Harbinger Capital Partners of New York this year. As of March, SkyTerra owed some $155 million to Boeing and said it would pay down some $55 million of that sum by September.

In addition to its Boeing debt, LightSquared would need to make a final payment to International Launch Services before the launch, and to purchase a launch insurance policy.

In response to Space News inquiries, Boeing on July 19 issued the following statement: “Due to several issues that will delay the launch of the SkyTerra 1 mobile broadband communications satellite, Boeing has opted to take advantage of the additional time available to perform additional testing on the SkyTerra 1 satellite. The parties involved have elected to exercise an abundance of caution before resuming the mission”

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