(Photo by MIKE SIEGEL/SEATTLE TIMES [WSB partner], republished with permission)

Hundreds watched it arrive in Elliott Bay, passing West Seattle shores late last night (WSB coverage here) – and this morning, the Sea-Based X-Band Radar (SBX) is in place at Vigor Shipyard (formerly Todd) on Harbor Island for three months of work – also visible from the West Seattle Bridge, as Brian Presser from TouchTech Systems observed while in this morning’s nightmare traffic (WSB coverage of THAT, here):

Hours after the SBX arrival, officials from the Missile Defense Agency and Vigor hosted media reps to get a somewhat closer look, though tours on board the facility itself were not offered. Army Col. Mark Arn, the SBX project manager for the MDA, explained a few things you might not have heard, even if you have been following our coverage over the past week. For one, a little more on why it’s here for the next 3 months: Routine maintenance, upgrades including power and radar – such as, enabling it to hook into shore power so its diesel generators don’t have to run ALL the time – and work on its thrusters, since it’s coming up on a “5-year certification renewal.” That requires a shipyard at a deep-water port (at least 50 feet), and Vigor qualified.

Yes, he reiterated, it won’t be operating while here. So what if somebody just accidentally flipped the switch? That can’t happen, Col. Arn insisted – putting it into operation requires a sequence of processes far beyond just pressing a button or flipping a switch. By the way, up to 100 people can live on board, though they have been closer to 85 lately. How sensitive is it, as a missile (or whatever) detector? He had an interesting analogy in this next minute-plus of video (the main questioner you hear is longtime aerospace reporter Glenn Farley from KING5), along with information on what’s under the dome:

Col. Arn said the SBX arrival here now also has to do with its schedule; it participates in missile-defense tests, including one less than a month ago. It’s the only one of its kind, and he said there are no current plans for another one; he mentioned its total cost in the vicinity of a billion dollars. The work at Vigor is estimated at $27 million.

ADDED 5:33 PM: One more view, from our friend Rebecca Nelson, who runs Ravenna Blog, has some nautical chops, and was first to tell us (about two weeks ago!) that something big was headed this way – a look from the water: