That system allows continuous communications with the launch vehicle. In the event of any problems with the launch, data from Argentia would allow the launch controllers to make a decision about destroying the rocket and payload.
and now for the trivia...
Ok, so maybe some of you are growing tired of the whole Titan 4B launch story, but as a guy who grew up when men on rockets were going to the moon, there is something about the whole thing that still captures my imagination.
The movie: Here is a link to NASA and some footage (no audio) in mpg format from the night launch of the Cassini probe. This launch used a Titan 4B and it is damned impressive. For those who may have missed it, the B-30 mission that caused such a fuss here this past week will be a night launch.
Note especially that towards the end of this clip, there is a bit of a flash. That is the solid fuel boosters separating a mere two minutes into the flight, on schedule. They drop back to the ocean. The payload is then taken to orbit by the sustainer, a liquid fueled vehicle based on the old Titan intercontinental ballistic missile.
The impact: I still haven't been able to confirm whether or not that sustainer breaks up on re-entry or lands intact. One source I'd trust has it that the thing comes down in one piece. That's actually better than bits and pieces, since there is an even higher level of confidence in where one big piece will go, as opposed to a bunch of little ones.
Personally, in that scenario, I'd still think there is almost no chance of any kind of explosion form whatever fuel remains on board, if any.
Tracking ships and launch monitoring: Having invested a lot of money into the rockets and the payloads, and as part of an overall monitoring system, the United States operates a number of missile tracking ships in the Atlantic and Pacific that spend their time down range during a launch gathering data. They feed back to the launch control centre so that there is never a time when the launch authorities don't know what is going on. It's part of the overall safety program to ensure launches are safe and that in the event of a problem, accurate information is flowing back to Florida in case the rocket must be destroyed in flight.
Here's one link. Scroll down to see all the vessel types. If memory serves, Observation Island was one of the ships I visited in the early 80s when it and another vessel, the Range Sentinel, were open to public tours during a port call.
Here's a link that discusses revitalization of launch facilities in Florida. "The USNS Redstone was deactivated on 6 August 1993, but a new range site was completed in Argentia, Newfoundland in June 1993 to support northbound flights of the TITAN IV from Cape Canaveral." [Emphasis added]
I'll have to check to see if this site is still active. Have a read through this history though; it gives tons of useful information on operations at Canaveral including range monitoring.
I also found a Powerpoint presentation from the late 1990s on command and control issues related to re-invigoration of the Canaveral launch complexes. It includes a prominent mention of Argentia and the so-called high-inclination launches. US NAVFAC Argentia closed in the early 1990s so odds are high as I write this that the Titan related site remained active for some time afterward and may still be there working busily away.
Update:
Further searching turned up the name of a company that provides communications support to Canaveral under contract. It's current corporate information package includes work at a site in Argentina, Newfoundland.
Just for the heck of it, here's a link to photos of the Island and a tiny bit of Labrador taken from STS-96. Kinda hard not to get a little awestruck at the beauty of the Earth from space. I feel a Tom Hanks moment coming on our voyage from the Earth to the moon.
If anyone out there is old enough to remember, there used to be a tracking and communications station at Shoe Cove used for the Apollo and Apollo-Soyuz programs in the 1970s. There's not much left but here is a link to some pictures of the Shoe Cove site as it stood recently.