Seven of the 72 Motorola mobile communications satellites launched into low earth orbit over the past 13 months have now failed, following the recent malfunctions of two additional spacecraft. Failure of a planned launch of a Delta booster carrying five satellites in August would jeopardise the scheduled start-up of the Iridium communications network.

The operational fleet of 66 Lockheed Martin-built satellites, in six orbital planes of 11 craft and one spare, has been reduced to 65, with no in-orbit spare now available following the recent setbacks.

Meanwhile, the US company has delayed the launch of a Chinese Long March 2C/SD booster carrying two spacecraft because, following the latest failures, it wants to finalise the satellites' orbital plane. The launch had been the first of a series planned to build up a stock of replacement satellites in an additional orbital parking plane.

A plan to launch a Delta II booster, equipped with four strap-on boosters, with three satellites, has been changed to fly five satellites on a standard nine strap-on booster model. Three of the satellites will replace a similar number of failed spacecraft in another orbital plane. Iridium will not be able to inaugurate the system on 23 September, as planned, unless the August launch is successful.

Source: Flight International