As the large wooden doors swung shut, Admiral Suluvana pulled a cell phone out of his pocket and punched in a well-remembered number. The call was answered on the second ring.
“Mustaf, the submarines are on their way. They will deal with the Americans,” Suluvana said.
Mustaf al Shatar answered, “That is good, but we need a back-up plan. I’ve put something in motion in Pearl Harbor, just in case your submarines fail. We will hit this Hunter where it hurts. We will take his family, then see what he does. My people will not fail.”
27 May 2000, 0243LT (1243Z)
Warran Jacobs reached for the black JA handset. He pushed the button, energizing a buzzer in Hunter's stateroom. “Captain, Officer of the Deck. Sonar reports a narrow-band frequency on the thin line towed array. Ambiguous bearings are three-four-one and zero-one-nine. Designated sierra two-one and sierra two-two. Frequency equates to a reactor coolant pump line from CHICAGO. I have stationed the section tracking party and have a line of bearings. Coming left to two-seven-zero to resolve bearing ambiguity.”
Jacobs leaned over the navigation plot, reading the information that his watch team was busy updating. The quartermaster was feverishly plotted each new bearing line as it was called out of sonar. The fire control technician analyzed the same information on the attack computer. The control room hummed with activity.
When sonar detected a contact on the towed array, the relative bearing of the noise signal could be from either side of the array. There was no way to immediately tell which side the contact was on. Therefore, there were always two different possible locations for the contact. The only way to resolve the ambiguity was to maneuver the ship and see where the contact showed back up. The problem was the array acted like a whip behind the sub. During, and for several minutes after a turn, the array was bent, so any signals were meaningless. Frequently, when the array was finally straight again, the signal would be gone. The search had to begin all over again.
Seated at his desk, Hunter digested the report. This would be a good test for the crew, a rare chance to use their skills against another boat.
“Very well, Officer of the Deck. Station the fire control tracking party. Be on the alert for any other contacts in the area. I will be right out,” he answered.
As Hunter walked the few steps into the control room, he could hear the muffled bustle of the crew scurrying to their battle stations.
“Steady on course two-seven-zero. Sonar, report when array is stable,” Bill Fagan, the fire control coordinator, muttered into his headset while directing the fire control tracking party.
Hunter saw the fire control party had been manned in just under two minutes and was attacking the problem.
Seaman Martinez brushed by, rubbing sleep out of his eyes, hurrying over to the ballast control panel, donning a sound powered phone headset to be the control room phone talker. The control room was calm and quiet despite the crowd of people trying to do their jobs.
Not bad, they are getting 'with the program', Hunter thought as he stepped up on to the periscope stand.
“Coordinator, sonar, array will be stable in five minutes,” the sonar supervisor answered Fagan.
Fagan turned toward Hunter and quietly murmured, “Captain, sonar reports five minutes to array stable. The contacts are sierra two-one last bearing three-four-four and sierra two-two last bearing zero-one-six. Frequency equates to CHICAGO’s reactor coolant pump line. No other contacts. No contacts in previously baffled area.”
Hunter responded “Very well, Coordinator. Any sign that CHICAGO has contact on us?”
“No indication, the frequency was stable right up until we turned. We should know for sure as soon as the array is stable,” the XO answered.
The sonar supervisor reported, “Coordinator, sonar, the array is stable, integrating.”
The array had settled out straight behind the sub again. The system began gathering data on the new course. It automatically integrated all the signals it received over a period of time so that it could maximize sensitivity and separate real contacts from random background noise. The system was so sensitive it would detect signal levels much weaker than the surrounding sea noise and several orders of magnitude below what the best sonar man could hear.
“Coordinator, sonar, regain of sierra two-one. Best bearing three-five-zero. Resolved ambiguity to the Northwest . Attempting to go into ATF on sierra two-one. No other contacts.”
Fagan murmured into the phone, “Sonar, Coordinator, aye,” and then announced to the fire control party, “Ambiguity has been resolved to sierra two-one bearing three-five-zero. Drop sierra two-two. Going into ATF on sierra two-one.”
ATF, the automatic target follower, allowed an electronic tracker to follow the contact automatically as it moved through the bearings. It gave the party a continuous update of the bearing to the contact. To do this, it needed a strong, stable signal.
They gathered and analyzed target data for several minutes to determine the general motion of CHICAGO relative to them. The process of determining the range, course and speed of a submarine using only passive sonar was a tedious, iterative one. Bearing to the CHICAGO and the received frequency were the only real information. Everything else was inferred. Gather bearing and frequency information for five or ten minutes on one course and then change course. Analyze many different possible solutions. Repeat the process until only one solution remained. Hopefully the correct one.
Through all the maneuvering and data gathering, the sub had to be kept at a range where the hunted would not counter-detect the hunter. Preferably, this was at the very edge of the detection range for the hunter's sonar and far back in the target's baffles; that cone behind his screw
