APLIS POSTCARD #14

25 March 2007

Position: 73-10N/145-50W

Temperature: -20ºF

Greetings from APLIS, adrift in the Arctic Ocean.

The Arctic Submarine Laboratory is located in San Diego. I bring this up because, if you’ve been watching the daily temperature readings I’ve been posting, you’ll have noticed that the temperatures have been dropping steadily. With winds above 10 knots, the wind chill all day has been pushing -40ºF. While this may leave many of you unimpressed, for somebody from Southern California IT’S COLD!!!!

Filling in a couple more areas I have just touched on before.

The thing that makes testing possible here at the camp is the tracking range. This is installed & operated by a team from APL University of Washington. Led by Tim Wen, this group includes Pete Sabin, Skip Kolve, and John Elliott.

Skip Kolve and Pete Sabin Runing the Tracking Range

The way the range works is really quite simple. Before we arrived, the APL/UW team installed hydrophones in four locations about 500 yards from the camp. Earlier still, they installed tracking range equipment and synchronized clocks aboard both boats. When on the range, the boats put out a sonar “ping” at a precise time which we know since we also have one of the synchronized clocks here at the camp. This allows the range computers to very accurately measure the time it takes the sonar signal to reach each of the four hydrophones. Knowing the speed of sound in water allows these times to be converted to ranges from each of the four hydrophones. Since we know exactly where the hydrophones are located, it allows the computer to produce the position of the submarine on an X,Y coordinate system. Our Range Safety Officers monitor these positions and pass them periodically to the submarines.

This system requires some tweaking in response to changes in the environment or the submarine’s range so one of the range technicians have been on duty around the clock for the last 10 days. When the ALEXANDRIA asked us to provide frequent range and bearing updates to them as they are approaching a surfacing site, the APL guys quickly produced a software change that allowed the computer to calculate this information automatically. They have been invaluable at helping us keep track of the submarines and keeping the two submarines a safe distance from each other.

Well, the VIPs got off the boat and headed back to Washington. ALEXANDRIA was especially interested in meeting Congressman Courtney from their home district in Connecticut.

While ALEX was on the surface, the Stargate people used it as a backdrop to do some filming. We also got in some additional testing that required the boat to be surfaced. George Chezmar from the Naval Undersea Warfare Center has been waiting here at APLIS for the opportunity to get aboard and test communications circuits. He got about half-way through before ALEX had to dive so he’ll finish at the next surfacing.

Stargate Actor Ben Browder Watches ALEXANDRIA Surface

Only a few more days left until we finish up and get to go home. But meantime, we’re staying warm.

Jeff Gossett

Arctic Submarine Laboratory