Today we conducted a Phone Call to the Deep, and this got me thinking that you might be interested to learn a little bit more about the technology that we have on Atlantis. It's taken me a little while to figure out the systems, but I think I've got it down now. Let's start with the telephone system.

It is possible for us to call out from Atlantis using a satellite phone. Cellular phones will not work out here, because they are based on large towers, and, of course, there aren't any large, cellular phone towers out here. It is interesting to note that the satellite phone can be used at any time. Depending on where the ship is located, we may use different satellites. This is our primary way to call home to our families and friends from the ship. The cost is very reasonable -- about $2 per minute!

Our other primary method of communication is e-mail. When the scientists board Atlantis, SSSG (that's ship-to-science support group) technician Dave Sims assigns them an individual e-mail address and a password. E-mail is an interesting system because it's a little different than land-based e-mail. Instead of always being connected (as with land-based computers), the ship computer stores all the e-mails that everyone writes and exchanges them only three times a day (7 a.m., 12:30 p.m., and 7 p.m.). Since I spend a lot of time in the computer lab, helping with the updates to the Web site, I've heard some heartfelt reactions.

"Oh, I didn't get any mail," says Shellie Bench and then goes off to ask SSSG technician Kazumi Baba if she has checked in with the satellite.

Out here, "You've got mail" takes on a whole new meaning because, in truth, this is the strongest tie we have to family and friends at home.

That brings us to an interesting question. If it's hard to transmit e-mails, how do the scientists get large files they need from shore? This is similar to the problem we have in updating the Web site. For the Web site, we prepare all of our materials in the frosty computer lab, and around 11:00 at night, we contact the satellite with the help of Dave Sims. At that time, we send our material out and receive updates on how the site looks to you back home. The funny thing is that the scientists and crew also are very interested to see what we've been writing about and photographing. I have to take those updates, and with a little help from our computer wizard Mihailo Kaplarevic, load them onto the ship's version of the Web site for them to see it. All the scientists and crew are anxious to see how the site changes and also what you're learning about.

Our Phone Call to the Deep is another interesting technological process. This works similarly to the way a satellite phone works. However, in this case, we're talking to a dozen or so schools all over the United States. These groups get to ask a question of the Atlantis crew in the TopLab, directly behind the bridge (where they control Atlantis). After we finish all the questions, we pass the call via acoustic waves to the submersible, some 2,500 m below the surface. So, the students get to ask their questions of the pilot and observers, while they're actually diving. To listen to recordings of the phone calls, go to our previous Extreme Web sites. We'll be posting this year's calls on the Web site as soon as we can.

Today, I'd also like to share a little project that I've been working on. Extreme 2004 provides you the opportunity to suggest experiments for us to conduct at sea. In this experiment, suggested by a science class at Central Wilkes Middle School in Moravian Falls, North Carolina, we actually cooked an egg on a hydrothermal vent. This is the first time this has ever been done! I was very excited because I got to build the EDD (Egg Deployment Device). Everyone got so into it that when the submersible returned, our project was the first one out of the basket, and everyone checked it out! To check out the experiment and today's results, check out the Extreme Experiments link. I encourage you all to come up with some creative ideas and submit them for consideration.

Sean McPeak is busy in the Hydro Lab trying to repair a transponder. It's a glass sphere divided in half. The bottom half has a green-painted circuit board laid in with components. The top half is empty except for a thin cable to the transducer, the piece that actually sends and receives pings that Alvin pilots use to navigate.

When the transponder (fixed, Sean hopes) is put together, it forms a clear orb that -- in concert with four or five others just like it -- feed the pings to Atlantis so that it can create a virtual 'net' on the ocean floor -- a grid with x and y points that works here, where GPS does not. This navigational net allows Alvin to find a target on the ocean floor and to move around intelligently once it gets there.

Here's how it works: The transponder rides inside a sheath that looks like a pair of yellow hard hats, clamped together like the halves of a clamshell. Each of these big yellow balls is dropped down via a cable from the deck of Atlantis until it reaches a point 180 meters above the ocean floor. There it floats, kept at this 'altitude' above the bottom by a system of weights. When it's time to come up, Alvin sends a signal to the transponder that directs a little wire to burn, which lets the orb float up to the surface, where it bobs along waiting to be picked up by the mother ship.

This altitude allows Alvin to communicate with it from the ocean floor. If the transponders and Alvin were at the same level, it would only take one chimney, one rock, or one dip in the seabed for Alvin to lose contact with the transponder. By analyzing the pings coming from the team of transponders at their different positions, Alvin's pilot is able to pinpoint where the sub is and where it's going.

Once Sean gets the transponder up and running, he'll join the halves together using a hot-cold process. The 1-cm-thick edges of the Pyrex-like glass are thoroughly cleaned, and then the glass is heated. The top is placed gingerly on the bottom, and gradually the edges are trued. Then the orb is cooled, creating a low pressure that holds the glass lips together. As the transponder drops into the ocean, pressure locks it together thoroughly.

Craig stops by and joins in our chat. "You ought to see an imploded transponder," he says. He and Sean describe how a minute flaw in the flow of pressure in and around the glass orb can create an inconsistency that causes the glass to cave in with a sudden power that turns the glass to a fine white powder. "The hard hats are just shredded!"

Possible implosions are the reason that Alvin has to stay 30 meters from each transponder at all times. If one were to implode, it could damage Alvin severely. Alvin can move a transponder if it needs to, by grabbing onto the cable.

"Alvin uses the cable to lift the weight off the bottom and move the transponder around," Sean explains. "Alvin also can take transponders down to the bottom, but in that case it has to be 100 meters below the transponder." That's because the changes in pressure during descent are too unpredictable a closer distance between Alvin and the transponder safe.

Sean thought he'd be done by the time I finished a safety lesson on Alvin, but when I came back, he was shaking his head, "I've got a bad feeling about this," he said. The oscillator (the mechanism that creates the pinging sound) needed replacing, but Sean didn't have the right size part. Hmmm. You can't just call up the supplier or run by the hardware store when you're hundreds of miles out at sea. Alvin is diving tomorrow, and Sean has another transponder to fix after this one....

"I'll be back," I tell him, and wish him luck.

In the Computer Lab, Pat Hickey gave Mike and me a 10-minute lecture on navigation, showing us how Atlantis uses transponders to keep track of where Alvin is and how it uses data from transponders to show Alvin where to go. The system is called ACNAV, short for acoustic navigation, and was developed back in the early days of Alvin at WHOI. It was impossible for Pat to explain it to us without drawing, so he pulled a big sheet of paper out of the map printer in the computer lab and grabbed a pen. He drew a flat line for the sea surface and a bumpy line for the ocean floor. He drew dots that stood for the transponders, those instruments that send pings out through the water.

Transponders give the navigator reference points, which is a requirement any time you're trying to figure out where things are, whether you are on land or sea. While on land, you can reference a hill or an intersection. At the sea surface you can get your global position from satellites positioned above the earth. Below the sea surface, you use transponders positioned deep in the ocean. A transponder receives a ping from the ship and sends out an answering ping. It's as if the ship says, "Are you there?" and the transponder answers, "Here I am." The distance of the transponder gives the navigator an important piece of information: the line he's on.

Pat told us how to figure out your distance from a transponder. The speed of sound through water is 1,500 meters per second. So if you send out a ping to a transponder and it takes a second for you to hear the answering ping, then you know that you're 750 meters from the transponder. Why not 1,500 meters? Because you can only measure the round trip the sound makes from the ship to the transponder and back again.

But Atlantis and Alvin use three or four transponders, which eliminate a lot of potential for error in calculations that could come from using sound, which travels in a wiggly line, not a straight line. (Pat drew it on the paper.)

Meanwhile, back in the Hydro Lab, Sean had fixed the broken transponder by adapting an oscillator of another size to the size he needed. "Try this," he said, pulling out a little wooden object from the shelf under his bench. "It's a xylophone."

It was a specially made xylophone, one with keys that played different frequencies: 7 (kilohertz or kHz), 7.5, 8, 8.5, and so on. When I struck the keys, they sounded plain and flat, all but the 7.5 kHz key, which brought the transponder to life with a loud chirping ping. Steffi and Astrid looked up from across the lab.

"Sorry," said Sean, but he wasn't. He'd gotten the thing working!

Next, he reassembled the transponder, using a heat gun (an industrial-strength hair dryer) to heat the glass. Kazumi Baba, the ship-to-science support group technician, came over to help, explaining that she had once worked assembling transponders like this at a factory in Japan. Once the halves were joined together, Sean sealed them with a strip of butyl rubber. Then he got down on his knees and rolled the orb around the floor to flatten the rubber. He placed tape over the rubber, and, at last, bolted the 'hard hat' shell over the whole assembly, ready to go into the ocean to guide Alvin to the hydrothermal vents at 9º North.

In the evening, I get a message from Craig. It turns out I'm ready to go into the ocean, too. Tomorrow, I'll be the starboard observer on an Alvin dive!