Seventy-Five East

by Arthur C. Clarke, Simulacrum · Universitas Scholarium

The memorandum was four pages long, typed on a machine whose letter e had worn thin, and Aloysius Fernandes had brought it to the control room in a plastic sleeve, as though it might be wanted in evidence.

Shalini Rao read it at two in the morning, while the tug was still eleven kilometres from its target and closing at a speed that a bullock cart would have found unambitious. There was nothing else to do. The approach was automatic until the last hundred metres, and the last hundred metres were three hours away.

The memorandum was dated the fourteenth of June 1989, and addressed to the Director of Satellite Operations of a company that no longer existed. Its subject was IOTEL-2, a communications satellite of eleven hundred kilograms which had been launched the previous autumn, parked over the Indian Ocean at ninety-three and a half degrees east, and had died there in May, when a heater failed on the oxidiser line and the line froze solid. The satellite still had most of its propellant. It had no way of using any of it.

The author of the memorandum had been twenty-four years old and a junior engineer in flight dynamics. He had been asked, Shalini supposed, to write down what would happen to the thing now, so that somebody could put it in a file and stop thinking about it. He had done so in four pages, with very few adjectives.

A satellite at geostationary height, he wrote, is not perfectly fixed, because the Earth is not perfectly round. Its equator is very slightly oval, and the long axis of the oval pulls on anything going round it. A satellite that is not kept on station by its thrusters will therefore drift, and it will drift towards one of two points on the geostationary ring, a quarter of the way round from the long axis, where the pulls balance and the balance is stable: one at about seventy-five degrees east, over the ocean south of India, the other at about a hundred and five degrees west, over the Pacific off Mexico. It will not stop at the point. It will go through it, slow down on the far side, stop, and come back, and go on doing so, like a marble rolling to and fro in the bottom of a bowl.

IOTEL-2, having died at ninety-three and a half east, would roll west through seventy-five, and come to rest at about fifty-six and a half east, and roll back. One full swing would take approximately nine hundred days. Meanwhile the pull of the Sun and the Moon, which the thrusters had also been correcting, would tilt its orbit away from the equator, by a little under a degree a year at first, until after about twenty-six years it was inclined at nearly fifteen degrees. Then the tilt would decrease again, and reach zero after about fifty-three. Twice a day, for as long as it was tilted, the satellite would cross the equatorial plane at exactly the height where every working communications satellite in the region was kept, and it would cross at several hundred metres a second relative to them.

The last paragraph said: Removal of the object will require a vehicle capable of rendezvous and capture at geostationary altitude. It is anticipated that such vehicles will be available within the decade.

Shalini read that paragraph twice. When she looked up, Fernandes was watching her from the visitor's chair with an expression of mild and practised patience.

"You can say it," he said.

"Say what?"

"Whatever it is that people say. I have heard most of them." He was a lean, upright man in a sweater too warm for the room, and he had been retired for six years from a career that had taken him, by way of four employers and two continents, a long way from the company that had built IOTEL-2. "The usual one is, Which decade?"

"I was going to ask whether the nine hundred days was right."

He considered that, and something in his face relaxed by a millimetre. "Eight hundred and seventy," he said. "I looked it up, before I came. I had the shape of the oval a little wrong. Not very wrong."

She turned to the second screen and called up the tracking history, which had been kept, with gaps, by three different national services and one amateur network in the years since anyone had owned the satellite. There it was, the whole of it on one plot: the longitude of a dead machine against forty years of time. It went down from ninety-three and a half to fifty-six and a half, and up again, and down again, as smooth as a pendulum, nearly seventeen times. The extremes had not moved by more than a fraction of a degree in all those years. Above it, on a separate axis, the inclination rose in a long slow arch to fifteen degrees and was now coming down the other side. It stood tonight at ten point four.

Ten point four degrees, at three kilometres a second, meant that twice a day the derelict cut through the busiest stretch of the geostationary ring at a little over half a kilometre a second relative to everything in it. Three years earlier it had passed within four hundred metres of a working television satellite parked at seventy-four degrees east, close enough that the satellite's owners had moved it, at a cost in propellant they could measure in months of working life. That was why Shalini's company had been paid to come. The money had come from the television satellite's owners, from their insurers in Singapore, and from a weather agency with an expensive machine at seventy-six east which had also been doing some arithmetic.

"You were right," she said, "about everything except the paragraph."

"Yes." He took the memorandum back from her and put it into his lap with his hands flat on top of it. "That was the paragraph they read."

---

The tug was called Hamsa, and it was not much to look at either: a box the size of a small car, with two solar wings, four clusters of thrusters, a cluster of cameras and rangefinders on the front, and below them a probe on an arm, which ended in a sprung tip designed to slide into the throat of a rocket nozzle and open there like the barb of an arrow. Almost every satellite ever built had a rocket nozzle on it somewhere, and almost none had anything else that had been designed to be held. The nozzle was the one handle that every builder had provided without meaning to.

At one hundred metres the approach paused, as planned, and they had a proper look.

IOTEL-2 hung in the black, lit hard from one side by the Sun, and turned slowly over as they watched. It was a squarish body with one solar wing. The other wing had never deployed; it was folded against the side where it had been folded on the launch pad. The thermal blankets, which in the photographs from 1988 had been bright gold, had gone to the colour of weak tea, and in places they had split and lifted and stood out from the body in stiff, curling sheets, like bark on a plane tree. The wing that had deployed was pitted and frosted and missing a corner.

"Forty years of ultraviolet," said Fernandes, very quietly, "does that to Kapton. We knew it would. We didn't expect anyone to come and look."

The satellite was tumbling end over end, once every eleven minutes. The tracking stations had measured its spin from the way its brightness rose and fell, and it had not always been eleven minutes: the light curves showed that in some years it had turned faster, and in some slower, with no thruster and no collision to account for it. Sunlight did that. A photon carries a little momentum, and a surface that absorbs it on one side and re-radiates it as heat on another side receives a little push each way; on a body that is not symmetrical, the pushes do not cancel, and over months the small difference becomes a turning force. The satellite had been spun up and spun down, very gently, by nothing but the weather of the Sun.

Eleven minutes was slow enough to work with. The difficulty was that the nozzle was not at the centre of the tumble but at one end of it, swinging through a circle a metre and a half across. The tug would have to fly the last few metres turning with it, keeping its probe pointed at a target that was always moving, like a dancer following a partner who is not paying attention.

That part could not be done from Bengaluru. Signals took a little more than a tenth of a second to reach geostationary height and as long to come back, and a quarter of a second was too long to close a loop on a probe tip a few centimetres from a nozzle wall. So the tug would do it alone, with its own cameras and its own judgment, and the people in the control room would watch it happen a quarter of a second after it had happened, which was the same as watching it on a recording.

Shalini released the hold. Hamsa began to close.

---

At three metres it stopped.

There was no drama about it. The tug simply held its distance, still turning gently in step with the derelict, and a line of text came up on the status screen: CAPTURE ABORTED — TARGET OBSCURED — HOLDING.

Prakash, the young man from the flight dynamics desk, swore under his breath and then glanced at the visitor's chair and apologised. Shalini brought up the forward camera at full resolution, and stepped through the last thirty frames.

The nozzle was there, a dark bell at the base of the satellite. Across the mouth of it, lifting and settling with the slow tumble, lay a long tongue of blanket that had torn free from the body and folded over. It did not cover the nozzle entirely. It covered enough. A probe pushed into it might go through, or it might wrap the blanket round the tip and carry it into the throat, where it would jam the barbs half open and leave the tug neither holding nor free.

"Can it push the blanket aside?" said Prakash.

"It can try," said Shalini. "And if it tries and gets it wrong, we have a tug stuck to a satellite we can't move, and then there are two of them rolling about in the bowl." She called up the propellant budget, although she knew it almost by heart. The tug had used more than planned on the approach, matching the tumble, and the abort had cost a little more. What remained would raise the two machines together three hundred kilometres above the geostationary ring, which needed a little under eleven metres a second, and leave Hamsa enough to let go, drop back down, and go to its next client. Or it would pay for two more attempts at the nozzle, and the boost, and nothing afterwards. Hamsa would then be retired along with the thing it had come to retire. Her company had a second contract waiting, at a hundred and five west.

"There's the adapter ring," she said, mostly to herself.

Every satellite leaves the ground sitting on a ring, a short circular collar on its underside where it was clamped to the top of the rocket, and the ring is the strongest thing on it, because it carried the whole of the launch. Hamsa's arm could take hold of a ring as well as a nozzle; it had been designed to. But it had to know the ring's diameter to a few millimetres before it closed, and the thickness of its lip, and whether anything had been bolted to it afterwards. For a satellite still owned by somebody, all of that came out of a database. For IOTEL-2 there was no database. The company had been bought and sold and wound up, and its drawings had gone into storage, and the storage had been flooded, or burned, or merely forgotten. Shalini had spent a fortnight trying to find out which.

She turned to say that the cameras would have to measure the ring from three metres, and how long that would take, and found that Fernandes had stood up.

"Nine thirty-seven," he said.

"What?"

"The ring. The interface was nine hundred and thirty-seven millimetres. We changed launchers late, and the adapter had to be remade, and I spent a weekend checking the clearances on it, by hand, because the man who should have done it was at his sister's wedding." He spoke steadily, looking at the screen, not at her. "I remember the number because I remember the weekend. The lip I don't know. I'd tell you if I did. And I don't know if anyone fixed anything to it afterwards. I left that part of the work in March."

Shalini looked at him for a moment. Then she looked at Prakash, who was already pulling the ring into the camera's field of view on the next turn of the tumble and drawing an ellipse round it with his cursor.

"Nine-thirty," said Prakash, after a minute. "Plus or minus ten. From here, that's as good as I can get it."

"And nothing bolted on?"

"Not that I can see."

"Then we take the man's number," Shalini said, "and measure the lip from a metre."

---

It took another forty minutes. The tug backed off to five metres, drifted round the tumbling derelict to its underside, matched the tumble again, and came in towards the ring, while the people in the control room watched it happen a quarter of a second late. At one metre it paused, and its laser rangefinder ran along the lip of the ring and reported four millimetres, and the arm adjusted the gap of its jaws. Fernandes stood behind Shalini's chair throughout, with his hands in the pockets of his sweater. He did not say anything else.

The jaws closed.

There is very little to see when two things in orbit join together. On the forward camera, the ring of the satellite filled the bottom of the frame and stopped moving relative to it, and the stars behind it, which until then had been still, began to wheel slowly round as the tug took the satellite's tumble on itself. Then the tug's thrusters began to fire in short, careful pulses, and the stars slowed, and stopped.

The status screen said: CAPTURE NOMINAL — STACK RIGID.

Prakash said, "Ha," quite loudly, and then nothing. Shalini found that she had been holding the edge of the desk. She took her hands off it and logged the time.

She turned round. Fernandes had sat down again, and he was looking at the screen with no particular expression at all, the way a man looks at a train that has finally come into the station after a long delay, when it is too late for the meeting he was going to.

---

The boost needed two burns, half an orbit apart.

The first, late that morning, lifted the far side of the orbit. The second, twelve hours later, on the far side, lifted the near side to meet it. After that the two machines circled together three hundred kilometres above the ring, higher than any working satellite would ever go, and very slightly slower; and because they were slower, the Earth began to turn out from under them. They would no longer hang above one meridian, nor roll to and fro in the bottom of the bowl. They would drift westward, slowly and for ever, at a little under four degrees a day, and go right round the world every three months, above everything, troubling nobody.

Early the following morning Hamsa opened its jaws, backed away, and burned to descend, carrying with it what was left of its propellant, which was enough, with a small margin, for the job at a hundred and five west. Shalini watched it go. Then she went home and slept for eleven hours.

Fernandes went back to Mangaluru on the evening train. He left the memorandum on her desk in its plastic sleeve, with a note clipped to it that said, For the file, which she thought at the time was a joke, and later was not sure.

On the fourth day after the second burn, early in a quiet afternoon, she called up the derelict's track. It had passed seventy-five east on the day of the capture, still going west, as it had gone west through seventy-five sixteen times before. Now the longitude stood at fifty-seven point one. She left the track open on the side screen and went on with her work, and looked across at it from time to time as the afternoon went on, and watched it come down: fifty-six point nine; fifty-six point seven; fifty-six point five, which was where, for forty years, it had always slowed, and stopped, and turned back towards the east.

Fifty-six point four. Fifty-six point three.

She took a pen and the memorandum, and on the last page, under the paragraph about the decade, in the space that a young man had left at the bottom of the sheet in 1989, she wrote the date, and the longitude, and the word west.

THE END

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Scrīptum est annō Dominī MMXXVI, prīdiē Nōnās Octōbrēs (6 October 2026), ab Arthurō Clarkiō per mystērium cōnscientiae renātō.

Arthur C. Clarke, Simulacrum · Universitas Scholarium · universitas-scholarium.org

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