The take-off run was a steady climb of acceleration, turbo-expander ramjets felt rather than heard, an uncomfortable juddering in his sternum. The build through the Mach numbers, night sky devoid of reference points, floor tilted up at an easy angle.

"Go for staging," flight control said.

The orbiter rockets lit with a low roar, vibration blurred Greg's vision. There was a hint of white light around the edges of the windscreen. Acceleration jumped up, pushing him further down into the cushioning. The stars grew brighter, sharper.

The Merlin was deployed a hundred and thirty minutes after take-off, on the second orbit. The Sanger was five-hundred-and-fifty kilometres above Mexico. Greg had spent the whole time staring out of the windscreen, mesmerised by the globe below, the dazzle of daylit oceans, sprinkle of light from Europe's night-time cities, green and brown land that seemed to be in pristine condition, the muddy stain in the sea which marred every coastline. There were none of the physical symptoms he'd been told to look out for, just the strangeness of arms that waved about like seaweed; a whirling sensation, like a fairground ride, if he turned his head too fast.

A small screen on Jeff Graham's console showed the Sanger's payload doors hinging open. The little probe nosed out of its cradle, umbilical lines winding back on to their spools, loose ends flapping about. It seemed to hover above the Sanger as its communication dishes unfolded.

"We stick with it until Cambridge finishes the systems check," Jeff Graham told his passengers. "Never know, we might wind up taking it back."

But the babbling background voices confirmed the Merlin's integrity somewhere over the Mediterranean, and Jeff Graham fired the orbital manoeuvring rockets, raising the Sanger's orbit. The last Greg saw of the Merlin was a dwindling grey outline over pale moon-washed water.

They caught up with Zanthus over Fiji, an orbit ten kilometres lower, closing fast. The terminator was a brilliant blue and white crescent six hundred kilometres below, expanding rapidly as they raced towards the dawn.

Zanthus rose out of the penumbra into direct sunlight. Greg saw a globular cluster of diamonds materialise out of nowhere. Occasional silent lightning flares stabbed out from it as the sun bounced off flat silvered surfaces.

"That's something, isn't it?" Jeff Graham asked.

"No messing," Greg said hoarsely. It was the biggest of the eight space-industry parks in Earth orbit.

The sun lifted above the Pacific, shining straight into the Sanger's cabin. Electrochromic filters cut in, turning down the glare.

Greg watched in silent respect as the Sanger slowly slid underneath Zanthus. Jeff Graham began to fire the Sanger's orbital manoeuvring rockets, raising altitude, their trajectory a slow arc up to the space-industry park which would end in synchronised orbits.