Hughes Satellite Failure Cause Is Still Unknown
Hughes Electronics Corp. on Tuesday said it may never know what caused a communications satellite to spin out of control in May, triggering a massive paging outage and affecting some U.S. video and radio broadcasts.
However, Hughes investigators have discovered what caused the failure of the disabled Galaxy 4’s back-up spacecraft control processor as well as the failure of similar components on two other orbiting satellites, the company said. Those two satellites--named Galaxy 7 and DBS-1--suffered control processor failures after the Galaxy 4 incident, but both spacecraft immediately switched to back-up systems without incident.
The control processors handle critical satellite functions such as solar wing positioning, antenna pointing and the spacecraft’s position relative to the Earth.
All the satellites involved are built by Hughes and are the company’s most popular model, with 35 in orbit and 30 more under construction or awaiting launch. The two Galaxy satellites are owned and operated by PanAmSat Corp. in Greenwich, Conn.
In each case, the spacecraft control processor gave out after an electrical short circuit caused by a series of unusual events, including the formation of tiny crystals on a tin-plated relay switch, Hughes said.
On Galaxy 4, the back-up control processor failed in that way about a year ago, but the outage was not noticed until the satellite’s main control processor failed inexplicably in May, the company said.
“We don’t know what caused the primary [controller] to fail,” said Richard Dore, spokesman for Hughes. “It almost appears to be a random failure.”
Dore said it is unlikely a spacecraft would lose both controllers again and become unusable. The Galaxy 4 outage, while sending shock waves to pager users, was the first time a functioning Hughes satellite gave out entirely.
The company said it no longer uses tin-plated relay switches and that the remaining satellites in orbit with the vulnerable switch are functioning normally.
“We believe the probability of an additional failure is very low,” said Dan Marcus, spokesman for PanAmSat. Still, the company has opted to launch additional back-up satellites and to build two other satellites that will stay on the ground until needed.
