PanAmSat’s Galaxy 7 Fails

Galaxy 7, located at 125°W, has ceased transmissions due to the failure of an onboard system responsible for controlling the spacecraft and maintaining its position relative to earth. No customer disruptions were reported. PanAmSat does not expect the satellite to resume operations. PanAmSat had been using the satellite as a backup to provide occasional services to the United States. Galaxy 7, a BSS 601 spacecraft built by Boeing Satellite Systems Inc., experienced the failure of its backup spacecraft control processor (SCP) at 1829 UTC (10:29 a.m. PST) on November 22. Its primary SCP failed in June 1998, but the satellite had continued to provide service using its backup SCP.

PanAmSat intends to file an insurance claim on the satellite, which is fully insured at a value of approximately US$130 million. Galaxy 7 was launched in October 1992 having an expected 12 year lifetime. The satellite carried 24 C-band and 24 Ku-band transponders used to distribute television programming and provide other telecommunication services across the entire United States and Caribbean.

Boeing, as Hughes Space and Communications, had previously concluded that SCPs on BSS 601 spacecraft launched prior to August 1997 contain tin-plated relay latching switches that act as on/off switches within the processors. Under certain conditions, a tiny, crystalline structure, less than the width of a human hair, can grow and bridge a relay terminal to its case, causing an electrical short. The problem has been solved in newer BSS 601 satellites by replacing the tin-plated switches with nickel-plated switches. Two SCPs are in each BSS 601 model spacecraft, but only one is required for operation of the satellite. The SCPs oversee the attitude control systems and the pointing of the solar arrays and antennas.

PanAmSat currently operates four satellites (other than Galaxy 7) with this design. One of these spacecraft, the PAS 4 Indian Ocean Region satellite, experienced the failure of its primary SCP in November 1998 and continues to provide seamless service on its backup SCP. PanAmSat plans to launch PAS 10 during the first quarter of 2001 to serve as the replacement for PAS 4 at 68.5°E. The three other spacecraft have fully operational primary and backup SCPs.  
  

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