kilometres a second then it’s only 30 × 86,400 × 15 = 39 million kilometres away now, a quarter of an AU, which makes it sixteen times brighter than it was at one AU. Herb, what’s the brightness of a one-kilometre asteroid at one AU?”
“Eighteen for a carbonaceous surface. Everybody knows that.”
Shafer was tapping at a pocket calculator. He said, “Inverse square brightness, forget phase angles. Yes, if Nemesis is a month from impact it could have magnitude fifteen. We should be able to pick it up now.”
Webb said, “Go for sixteen or seventeen visual and we cut the exposure times to seconds. We might even have a continuous scan. We could cover the sky in a week. It’s then down to bad luck, like coming at us out of the sun or approaching from the south.”
McNally’s slim fingers were agitatedly drumming on the table. “Can we inject some realism into this? If we’re a month from impact what am I supposed to do about it? Call up Superman? I need a year minimum, preferably two or three, to build some hardware.”
“But if Nemesis is a year from impact now, we’ll still only detect it in eleven months’ time, when it’s on the way in. A last-minute deflection is the only scenario you can work on.”
“Let me understand this,” Noordhof said. “If you guys are right, the chances are hundreds to one against our finding this thing in the next five days. Unless it’s so close that it’s maybe a month or two from impact. And even then maybe not if it’s coming at us out of the sun.”
There was a silent consensus around the table.
“Shit,” Noordhof added, looking worried. He turned to the Director of NASA. “McNally, you have to come up with a deflection strategy based on the month-from-impact scenario.”
“For Christ’s sake, that’s just off the wall.” The NASA director’s face was flushed.
Firmly: “You have no choice in the matter.” Noordhof was playing nervously with his unlit cigar. Webb had a momentary vision of Captain Queeg rolling little metal balls in his hand.
“Jim,” Shafer’s tone was conciliatory. “We’re the A team. Maybe you and I can come up with something.”
McNally shook his head angrily.
Leclerc asked, to break the tension, “What would happen if say somebody in Japan found an asteroid?”
“The whole astronomical community would know it within hours,” Sacheverell said. “Civilian discoveries go straight to the Minor Planet Center which has electronic distribution to all the major observatories. But look, forget Japan, Europe and Atens and crap like that. The action is at Lowell, Spacewatch and Hawaii”—Kowalski winced slightly, but said nothing—“and we’re linked in to these places here. We’ll see the exposures build up in real time.”
Webb said, “Detection isn’t enough. If we don’t follow it up, we lose it. We have to track it long enough to get a reliable orbit.”
Sacheverell said, “Follow-up means we come back to it every few hours, using the interval in between to search for other asteroids. An interval of a few hours gives you its drift against the stars enough to pick it up again the following night. To get a believable orbit, you need to track it for at least a week. To get decent precision, say to launch a probe at it, you have to update over months. There are follow-up telescopes in British Columbia, Oak Ridge Massachusetts and the Czech Republic. Also at Maui.”
Kowalski nodded. “We’re well placed for follow-up here. Our Grubb Parsons has a long focal length and its point spread function is small. On a good night we can do very high-precision astrometry.”
“The Grubb Parsons is vital,” Webb agreed. “Without it follow-up would double the load on the discovery telescopes.”
Leclerc, pen hovering over his Filofax, asked again: “Suppose you find an asteroid and follow it up. What then?”
Webb said, “Nearly every one we find will be harmless. We’re looking for a needle in a field of haystacks.
“Eighteen for a carbonaceous surface. Everybody knows that.”
Shafer was tapping at a pocket calculator. He said, “Inverse square brightness, forget phase angles. Yes, if Nemesis is a month from impact it could have magnitude fifteen. We should be able to pick it up now.”
Webb said, “Go for sixteen or seventeen visual and we cut the exposure times to seconds. We might even have a continuous scan. We could cover the sky in a week. It’s then down to bad luck, like coming at us out of the sun or approaching from the south.”
McNally’s slim fingers were agitatedly drumming on the table. “Can we inject some realism into this? If we’re a month from impact what am I supposed to do about it? Call up Superman? I need a year minimum, preferably two or three, to build some hardware.”
“But if Nemesis is a year from impact now, we’ll still only detect it in eleven months’ time, when it’s on the way in. A last-minute deflection is the only scenario you can work on.”
“Let me understand this,” Noordhof said. “If you guys are right, the chances are hundreds to one against our finding this thing in the next five days. Unless it’s so close that it’s maybe a month or two from impact. And even then maybe not if it’s coming at us out of the sun.”
There was a silent consensus around the table.
“Shit,” Noordhof added, looking worried. He turned to the Director of NASA. “McNally, you have to come up with a deflection strategy based on the month-from-impact scenario.”
“For Christ’s sake, that’s just off the wall.” The NASA director’s face was flushed.
Firmly: “You have no choice in the matter.” Noordhof was playing nervously with his unlit cigar. Webb had a momentary vision of Captain Queeg rolling little metal balls in his hand.
“Jim,” Shafer’s tone was conciliatory. “We’re the A team. Maybe you and I can come up with something.”
McNally shook his head angrily.
Leclerc asked, to break the tension, “What would happen if say somebody in Japan found an asteroid?”
“The whole astronomical community would know it within hours,” Sacheverell said. “Civilian discoveries go straight to the Minor Planet Center which has electronic distribution to all the major observatories. But look, forget Japan, Europe and Atens and crap like that. The action is at Lowell, Spacewatch and Hawaii”—Kowalski winced slightly, but said nothing—“and we’re linked in to these places here. We’ll see the exposures build up in real time.”
Webb said, “Detection isn’t enough. If we don’t follow it up, we lose it. We have to track it long enough to get a reliable orbit.”
Sacheverell said, “Follow-up means we come back to it every few hours, using the interval in between to search for other asteroids. An interval of a few hours gives you its drift against the stars enough to pick it up again the following night. To get a believable orbit, you need to track it for at least a week. To get decent precision, say to launch a probe at it, you have to update over months. There are follow-up telescopes in British Columbia, Oak Ridge Massachusetts and the Czech Republic. Also at Maui.”
Kowalski nodded. “We’re well placed for follow-up here. Our Grubb Parsons has a long focal length and its point spread function is small. On a good night we can do very high-precision astrometry.”
“The Grubb Parsons is vital,” Webb agreed. “Without it follow-up would double the load on the discovery telescopes.”
Leclerc, pen hovering over his Filofax, asked again: “Suppose you find an asteroid and follow it up. What then?”
Webb said, “Nearly every one we find will be harmless. We’re looking for a needle in a field of haystacks.
Similar Books
