Another former Hughes Space and Communications (HSC) - now Boeing Space Systems - 601 series spacecraft, DirecTV 3, has been hit by what appears to be a generic spacecraft control processor (SCP) fault. The problem has been found in 25 of this model of satellite built before mid-1997.
DirecTV 3, launched in June 1995, will become an in-orbit spare after suffering an SCP shutdown. Traffic has been diverted to DirecTV 4. With the recent Proton launch of DirecTV 5, the broadcasting company has operational satellites at 101°W, 110°W and two at 119°W in geostationary orbit. DirecTV 7S will be launched by an Ariane 5 next year.
The 601-based Galaxy IV, Galaxy VII and Solidaridad 1 satellites have already been written off as total losses after prime and back-up SCP failures. DirecTV 1, DirecTV 3, PanAmSat 4 and Galaxy IIIR have experienced single SCP failures.
The problem results from electrical shorts caused by tin-plated relay latching switches that act as on-off switches in the prime and back-up SCPs.
HSC found that a tiny crystalline structure, less than the width of a hair, can grow and bridge a relay terminal to its case, causing an electrical short. Boeing now uses nickel-plate switches and improved processes, which appear to have corrected processor faults on later 601 models.
Ball Aerospace and Technology has been selected to build: a National Polar Orbiting Operational Environment Satellite System (NPOESS); preparatory project spacecraft to provide a first flight opportunity for three NPOESS instruments; microwave and infrared sounders; and a visible/infrared imager radiometer. They will fly on the satellite in 2006.Source: Flight International
