There's a problem with a vernier thruster heater. I'm not familiar enough with the commit criteria to know if that could result in a launch scrub. It's certainly not something that can be easily worked on the pad, but there may be sufficient redundancy that they could go anyway. The problem is that for many missions in the past, verniers aren't necessarily required, but I suspect they don't want to try to dock to ISS if they're missing one.

We haven't left for the Cape yet. We may drive up anyway, just for the drive, and hope for the best, since it will likely be windy and rainy here the rest of the weekend.

By the way, the gang of Florida Today reporters over at The Flame Trench is probably the best place to keep tabs on the launch, at least as far as blogs go.

[Update a few minutes later]

Can't be fixed on the pad, as I suspected. They're figuring out now if they can live without it, if necessary. There are so many thrusters on the vehicle (though a lot more primaries than verniers), that I'd guess they can come up with a workaround control scheme.

The problem is either with the thermostat or heater. The heater was supposed to read hot, but it read ambient.

I wonder how they know that it's not just a failed temperature sensor?

I wonder how they know that it's not just a failed temperature sensor?

My guess would be the sensor is still correctly indicating the am-bient temperature, and changes in that temperature.

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