LOFAR is an acronym for Low Frequency Analysis and Recording.
It’s a method of acoustic processing that takes the noise detected by a sonar sensor and strips it apart into individual component frequencies. By comparing those frequencies against a catalogue of known acoustic sources, it is often possible to classify the source of a particular noise.
A skilled acoustic analyst can read a LOFAR gram the way an average person reads a newspaper. The process is largely one of elimination.
Three-bladed propellers have different characteristics than four-bladed propellers. Engines with in-line cylinders generate different frequencies than V-configured engines. Four-pole electric motors make different tonals than two-pole motors. Chinese-built ventilation fans are different from French-built fans, which are different from Russian-built fans.
Different hull designs have different hydrodynamic characteristics, which create identifiable sounds.
Sometimes, the majority of the contact's frequencies are common to several possible sources and the resulting classification may be ambiguous:
From their display consoles, the two Acoustic Sensor Operators began the process of classifying the frequencies coming in from the sonobuoys.
After several minutes, George’s voice came over Shari’s headset. “All buoys are
Shari and Andy stared at each other in disbelief. “Say again,” Shari said.
“I repeat,” the TACO said, “all buoys are cold.”
“All of them?” Andy asked softly.
“Every one of them,” George said. “The only tonals we’ve got are coming from those two yachts, and that merchant ship. We have zero possible submarine contacts.”
“Have your guys go over the grams again,” Shari said. “Maybe they’re missing something.”
“They’ve been over them twice,” George said. “Then I went over them myself. Those grams are ice cold.”
Shari’s eyes went to the Tactical Data Display. “Check the numbers, Andy. First you do them, and then give them back to Nav for a cross-check. While you’re at it, get Nav to run a diagnostic on GPS. Maybe we planted the Briar Patch in the wrong spot.”
“I’ll check, boss,” Andy said. “But I’ve never seen a GPS plot that was off by more than a few inches.” He flipped a selector switch and began talking to the Navigator on another circuit.
Shari keyed her mike. “George, have your ASOs run diagnostics on their gear.”
“Already in progress,” the TACO said, “but I can tell you up front that the equipment is running sweet. Whatever’s wrong ain’t in the ARR-78s.”
“Let’s swing back and re-seed that bad buoy,” Shari said.
“That’s not it,” George said. “There isn’t enough room in the blind zone for one sub to hide, much less
“Maybe all four of them aren’t down here,” Shari said.
Andy kept his eyes on the TDD and punched buttons, watching the changing numbers like a hawk. He keyed back into Shari’s intercom circuit. “That’s certainly a possibility. But AEW got solid ES cuts on at least two of their radars. Even if there
“If anyone’s got a better explanation,” Shari said, “I’d love to hear it right now.”
“These new 212Bs are supposed to be bad-ass,” Andy said. “Maybe they’re just so quiet that we can’t detect them.”
“I can’t rule that out,” George said. “But I’ll believe it when I’ve seen the proof.”
“Could be we’re seeing it now,” Shari said. “Or not seeing it, as the case may be.”
“The Brits detected them by going active,” Andy said. “Maybe we need to drop some active buoys.”
“Not my first choice,” George said. “As soon as we start pinging, those subs are going to run like scalded dogs. If they split up, we’ll never catch them all.”
Shari stared out the window at the Mediterranean. The water was still just as blue as it had been before, but now her eyes accused the waves of concealing the location of her enemies. “It’s not like we’re having a hell of a lot of luck catching them now,” she said.
Andy looked up from the TDD. “The numbers are clean. We dropped those buoys right on top of the ES cross-fix.”
George said, “Maybe the cross-fix was wrong. Who says the AEW guys can’t screw the pooch once in a while?”
“Maybe,” Shari said, “but they’re never going to admit it. Let’s set up a rack of active buoys and try this again.”
“Yes ma’am,” George said, but his voice didn’t sound very confident.
Shari pretended not to notice. “Shoot me some waypoints.”
Active buoy number 9 was going into the water when George said, “
“Where the hell are they?” Shari asked.
“Just a second,” George said. “I’m getting the cross-fix now.”
Shari waited without speaking; the only sound in the cockpit was the drone of the engines.
After what seemed like an hour, but was — in reality — probably more like five minutes, the accordion door at the rear of the cockpit slid open.
George stepped into the cockpit and stood in the narrow strip of floor space between the pilot and copilot chairs. His disconnected comm-set was down around his neck, the cord draped around his shoulders. “Ah, boss?”
Shari looked up. George never came up to the flight deck to deliver good news. “I’m not going to like this, am I?” she asked.
“Afraid not, boss. We plotted the cross-fixes on those I-band radars we’ve been chasing. They fall right on top of those two yachts in the middle of our Briar Patch.”
“That’s nuts,” Shari said. “Go out to AEW and get them to check their ES gear.”
“I’ve already done that,” George said. “Their gear is clean. Those boats are emitting I-band radar signatures consistent with German Type 212B diesel submarines.”
“Leave it to the AEW weenies to screw up something simple like an ES cut.”
The idea dawned on Shari slowly, like some sort of vile egg hatching deep in her intestines. “AEW didn’t screw up,” she said. “They got suckered. We
“Those boats are carrying decoy radar emitters,” George said softly.
Shari’s eyes shot over to Andy. “Get on the horn to the
Andy picked up the radio microphone, his face gone suddenly the color of ash. “It’s already too late, isn’t it? The subs have already gotten past us.”
“Forget about us,” Shari said. “The carrier is out of position,
CHAPTER 17
