Rendezvous With Rama - Arthur C. Clarke Page 0,1

catalogued as 31/439, according to the year and the order of its discovery, was detected while it was still outside the orbit of Jupiter. There was nothing unusual about its location; many asteroids went beyond Saturn before turning once more toward their distant master, the Sun. And Thule II, most far-ranging of all, traveled so close to Uranus that it might well be a lost moon of that planet.

But a first radar contact at such a distance was unprecedented; clearly, 31/439 must be of exceptional size. From the strength of the echo, the computers deduced a diameter of at least forty kilometers. Such a giant had not been discovered for a hundred years. That it had been overlooked for so long seemed incredible.

Then the orbit was calculated, and the mystery was resolved—to be replaced by a greater one. 31/439 was not traveling on a normal asteroidal path, along an ellipse which it retraced with clockwork precision every few years. It was a lonely wanderer among the stars, making its first and last visit to the solar system—for it was moving so swiftly that the gravitational field of the Sun could never capture it. It would flash inward past the orbits of Jupiter, Mars, Earth, Venus, and Mercury, gaining speed as it did so, until it rounded the Sun and headed out once again into the unknown.

It was at this point that the computers started flashing their “We have something interesting” sign, and, for the first time, 31/439 came to the attention of human beings. There was a brief flurry of excitement at SPACEGUARD headquarters, and the interstellar vagabond was quickly dignified by a name instead of a mere number. Long ago, the astronomers had exhausted Greek and Roman mythology; now they were working through the Hindu pantheon. And so 31/439 was christened Rama.

For a few days, the news media made a fuss over the visitor, but they were badly handicapped by the sparsity of information. Only two facts were known about Rama: its unusual orbit and its approximate size. Even this last was merely an educated guess, based upon the strength of the radar echo. Through the telescope, Rama still appeared as a faint, fifteenth-magnitude star—much too small to show a visible disc. But as it plunged in toward the heart of the solar system, it would grow brighter and larger month by month; before it vanished forever, the orbiting observatories would be able to gather more precise information about its shape and size. There was plenty of time, and perhaps during the next few years some spaceship on its ordinary business might be routed close enough to get good photographs. An actual rendezvous was most unlikely; the energy cost would be far too great to permit physical contact with an object cutting across the orbits of the planets at more than a hundred thousand kilometers an hour.

So the world soon forgot about Rama. But the astronomers did not. Their excitement grew with the passing months as the new asteroid presented them with more and more puzzles.

First of all, there was the problem of Rama’s light curve. It didn’t have one.

All known asteroids, without exception, showed a slow variation in their brilliance, waxing and waning in a period of a few hours. It had been recognized for more than two centuries that this was an inevitable result of their spin and their irregular shape. As they toppled end over end along their orbits, the reflecting surfaces they presented to the sun were continually changing, and their brightness varied accordingly.

Rama showed no such changes. Either it was not spinning at all or it was perfectly symmetrical. Both explanations seemed unlikely.

There the matter rested for several months, because none of the big orbiting telescopes could be spared from their regular job of peering into the remote depths of the universe. Space astronomy was an expensive hobby, and time on a large instrument could easily cost a thousand dollars a minute. Dr. William Stenton would never have been able to grab the Farside two-hundred-meter reflector for a full quarter of an hour if a more important program had not been temporarily derailed by the failure of a fifty-cent capacitor. One astronomer’s bad luck was his good fortune.

Stenton did not know what he had caught until the next day, when he was able to get computer time to process his results. Even when they were finally flashed on his display screen, it took him several minutes to understand what they meant.

The sunlight reflected from