Friday, January 14, 2011

Intelsat Galaxy-15 a.k.a. "ZombieSat" Returns!

Great day for Intelsat! The Galaxy-15 bird, which stopped responding to ground commands last April 5th and was drifting across the "Orbital Parking Slots" of other satellites, is now responding to ground commands.
This was first thought to have been caused by a solar-flare event, but subsequent ground testing (and a LOT of head scratching!) has determined it was caused by an ESD event. "ESD" stands for "Electro Static Discharge", the same thing that happens when you shuffle across the carpet, grab a door knob or other grounded item, and get zapped. Actually, the other object doesn't have to be grounded, just at a lower electrical potential than you are, and current will flow.
The breakthrough was caused when the satellite's inertial wheels (a method of stabilizing the space craft....think big gyroscope) had absorbed all the momentum they could absorb, and could no longer keep the spacecraft properly oriented with respect to the Earth and the Sun. With the solar panels now pointing away from the sun and not generated any power, the batteries became depleted to the point that the onboard computer caused a reset of all the systems on the satellite, which cleared the fault, and allowed the satellite to begin functioning normally, and respond to ground commands again.
They were very lucky that the ESD event apparently didn't do any permanent damage, like blowing out a bunch of stuff, but instead caused a certain part of the onboard computer to lock-up and ignore ground commands. Once it reset itself and cleared the fault it started operating again.

More here:

Intelsat Galaxy-15 Returns To Service
Build-Up Of Static Electricity Turned Satellite Into Zombie
Intelsat Galaxy-15 Drifts From Zombie To Phoenix-like Recovery

3 comments:

  1. Or perhaps the Borg are done with it, and will now commence their invasion. Ya never know!

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  2. I used to follow satellite news back when I was a C-band subscriber. When C-band started losing channels I wanted to watch (think NASCAR coverage), it seemed best to be assimilated by the K-band Borg.

    The ol' dish was parked at G-5 most of the time anyways.

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