spacetoday.net: Proton failure blamed on programming error

Posted: Wed, Aug 31, 2011, 7:56 PM ET (2356 GMT)
Proton-M launch of Express-AM4 (Roscosmos)

The loss of a communications satellite launched on a Proton rocket earlier this month has been blamed on a programming error in the guidance system of the rocket's upper stage, Russian officials said Tuesday. The Express-AM4 satellite was stranded in a transfer orbit when its Breeze-M upper stage failed to complete a series of five engine burns. The Russian space agency Roskosmos announced that investigators traced the failure to a guidance error in the upper stage that put it into the wrong orientation and thus injected the satellite into an "off-design" orbit. Russian officials have lifted the ban on Proton launches with "appropriate recommendations" to prevent the problem from happening again. The Express-AM4 satellite has been declared a total loss, though, since it cannot be moved to geosynchronous orbit. The Proton/Breeze-M failure is not related to last week's failed launch of a Progress spacecraft on a Soyuz rocket; that failure was in the gas generator in the rocket's upper stage, although investigators have yet to find the specific cause of the failure.