January 14, 2011
Zombie Satellite Becoming Functional Again
Intelsat reported today that its Zombie Galaxy-15 satellite is now under full command again and set for an intense testing program.
According to Intelsat, the satellite could return to the business of relaying TV services to the U.S. if it is given a clean bill of health.The spacecraft's recent troubles have had hardly any impact on its fuel reserves.
"The current end of life is 2022; that isn't going to change," said Tobias Nassif, Intelsat's vice president of satellite operations and engineering.
"We did save a little fuel in east-west station-keeping over the past eight months; however we'll now use that fuel to bring the satellite back into its station. So the net effect is essentially zero," he told BBC News.
The investigation into the mishap suggests that an electrostatic discharge on the spacecraft may have been at the root of the platform's problems.
The zombie satellite was launched into space in 2005 to a position high above the equator.
Its mission was to re-distribute TV services to cable companies across North and Central America, and also to send navigation data to airplanes to improve the accuracy of their GPS receivers.
However, on April 5 last year the spacecraft experienced a major glitch that left it incapable of sending telemetry or taking commands.
Galaxy-15 retained a fully functional electronics payload and its capability to re-transmit on full power any TV signal it received of compatible frequency soon became a cause of concern among satellite operators.
The telecommunications satellite's "dead-but-alive" condition earned the Intelsat spacecraft the unfortunate nickname of "zombie-sat" in some quarters.
The Galaxy-15 ceased to become a hazard once it lost the ability to orient itself and lock on the Earth. This took longer than expected but the solar arrays on the spacecraft also then lost sight of the Sun and the electronics payload soon went into shutdown as the batteries drained.
A reset maneuver that followed engineers to upload software patches and take back full command. Total control was re-established at the end of December.
The zombie satellite has been instructed to move into position at 93 degrees West. Intelsat will undertake a series of tests not unlike those given to brand new spacecraft in their post-launch commissioning phase.
"Keep in mind the satellite for eight and a half months was fully functional; it was never during that period in any kind of state of stress," Nassif told BBC. "Therefore, we don't expect there to be any damage to the spacecraft. However, we're going through this whole testing."
The board of inquiry set up to investigate the incident should deliver its findings in February.
Laboratory tests by spacecraft manufacturer Orbital Sciences have established that software issues left Galaxy-15 vulnerable to determine if there was an electrostatic discharge (ESD) of a particular energy within the satellite.
Intelsat said the suggestion that intense solar activity at the time of the outage has been dismissed.
"Many of the anomalies that operators experience onboard [their satellites] ultimately get attributed to ESD events," Nassif told reporters. "Satellites are built to the best understanding of the space environment and as we learn more about operating in space and the harshness of space satellite manufactures will apply those lessons to future designs."
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