Thunderhead

“Can I ask how you did it?”

“I took the raw data from the shuttle feed this morning and burned an extra copy onto the disk. I’ve always got a handful of disks in my backpack; nobody would know the difference.” He waggled the disk and it flashed in the dim light, sending out a coruscation of color. “If you have the right clearance, stealing data isn’t difficult. It’s just that, if you get caught, the penalties are much stiffer. Much stiffer.” He grimaced.

“I realize that,” said Nora. “Thank you, Peter.”

He looked at her. “You knew I’d help, didn’t you? Even before you left the pizza parlor.”

Nora returned the glance. It was true; once he’d described the way he could access the data, she felt certain he’d agree. But she did not want to hurt his pride. “I hoped you would,” she replied. “But I wasn’t really sure until you called the next morning. And I can’t tell you how much I appreciate it.”

Nora realized Holroyd was blushing. He quickly turned his back and opened the refrigerator door. Inside, Nora could see two cans of alcohol-free beer, some V8 juice, and a large computer CPU. Looking more closely, she noticed the computer was co

“Too hot out here,” Holroyd said, sliding the disk into the computer housing and closing the refrigerator door. “Put your topo over there, okay?”

Nora began to unroll the map, then paused. “You realize this won’t be like crunching numbers all day long in an air-conditioned lab,” she said. “On a small dig like this, everybody does double or triple duty. You’d be coming along as an assistant, specializing in image sensing. Only they’re not called ‘assistants’ on archaeological digs. They’re called ‘diggers.’ For a reason.”

Holroyd blinked at her. “What are you trying to do? Talk me out of going?”

“I just want to make sure you know what you’re getting into.”

“You’ve seen the books I read. I know it won’t be a picnic. That’s part of the challenge, isn’t it?” He sat down at the wooden table and pulled the keyboard toward him. “I’m risking a possible prison sentence, bringing you this data. You think I’m afraid of a little digging?”

Nora smiled. “Point taken.” She pulled up a plastic chair. “Now how does this thing work, exactly?”

“Radar’s just another kind of light. We shine it down on Earth from the shuttle, and it bounces back changed. The Terrestrial Imager simply takes digital photographs of what bounces back, and then combines them.” Holroyd punched some keys. There was a brief pause, then a small window opened at the bottom of the screen, displaying scrolling messages as a complex program began to boot. Several other small windows flew open in corners of the screen, displaying various software tools. Then a large window appeared at the screen’s center. Holroyd moused the cursor through several menus. Finally, an image began rolling down the large central screen, line by line, painted in artificial reds.

“Is that it?” Nora stared at the screen in disappointment. This was the last thing she’d expected: confusing monochromatic patterns like no landscape she had ever seen.

“It’s just the begi

“And then we’ll be able to see the road?”

Holroyd gave her an amused look. “If only it were that simple. We’re going to have to beat the shit out of the data before we can see the road.” He pointed. “This red is L-Band radar. It has a wavelength of twenty-five centimeters and can penetrate five meters of dry sand. Next, I’ll add C-Band.”

A blue color scrolled down.

“This C-Band has a six-centimeter wavelength, and it can penetrate at most two meters. So what you see here is a little shallower.” More key taps. “And here goes X-Band. That’s three centimeters. Basically, it gives you the surface itself.”

A neon green color rolled down the screen.

“I don’t see how you can even begin to figure all this out,” said Nora, gazing at the distorted swaths of colors.

“Now I’m going to paint in the polarizations. The outgoing radar beam is polarized either horizontally or vertically. Sometimes you send down a beam horizontally polarized, and it bounces back vertically polarized. That usually happens when the beam encounters a lot of vertical tree trunks.”

Nora watched as another color was added to the screen. It was taking longer for the program to paint the image on the screen; obviously, the computational problem was becoming more complex.

“Looks like a de Kooning,” said Nora.

“A what?”

Nora waved her hand. “Never mind.”

Holroyd turned back to the screen. “What we’ve got is a composite image of the ground, from the surface to about fifteen feet deep. Now it’s a matter of canceling out some of the wavelengths and multiplying others. This is where the real artistry comes in.” Nora could hear a touch of pride in his voice.

He began typing again, more quickly this time. Nora watched as a new window opened on the screen, lines of computer code racing as routines were added and deleted. The remote desert vastness was suddenly covered by a thin web of tracks.

“My God!” Nora cried. “There they are! I had no idea the Anasazi—”

“Hold on a minute,” interrupted Holroyd. “Those are modern trails.”

“But this area isn’t supposed to have any roads.”

Holroyd shook his head. “Some of these are probably wild horse trails, deer trails, coyote trails, mountain lion trails, maybe even four-wheel-drive tracks. There was some prospecting for uranium in this area in the fifties. Most of these tracks you wouldn’t be able to see on the ground.”

Nora slumped back in her chair. “With all those trails, how can we ever find the Anasazi one?”

Holroyd gri

He continued to type. “No one knows why, but sometimes dramatic things happen if you multiply the values of two wavelengths together, or divide them by each other, or cube one and take the square root of another and subtract the cosine of your mother’s age.”

“Doesn’t sound very scientific,” said Nora.

Holroyd gri

He worked with steady determination. Every few minutes the image changed: sometimes dramatically, sometimes subtly. Once Nora asked a question, but Holroyd merely shook his head, brow furrowed. At times, all the roads vanished; Holroyd would curse, type a flurry of commands, and the roads returned.

Time crawled by, and Holroyd grew increasingly frustrated. The sweat stood out on his brow, and his hands flew across the keys, hitting them with greater force. Nora’s back began to ache, and she found herself shifting constantly in the cheap chair, trying to find a comfortable position.

At last, Holroyd sat back with a muttered curse. “I’ve tried all the methods, all the tricks. The data just won’t put out.”

“What do you mean?”

“Either I get a million roads and trails, or I get nothing.” He got up and went to the refrigerator. “Beer?”

“Sure.” Nora glanced at the clock. It was seven, but the apartment was still insufferably hot.

Holroyd sat down again, passing her the beer and propping a leg up on the computer table. A knobby ankle protruded from below the cuff, pale and hairless. “Is there anything unusual about the Anasazi roads? Something that might differentiate them from all these animal trails and modern stuff?”