It takes just seven pixels to ratchet up the tension. Together, the seven create a small, elongated knot on a computer screen in the European Space Operations Centre, Darmstadt, Germany. This is the European Space Agency's equivalent of NASA's Houston Mission Control.
Situated in a faceless business park near the city's train station, it isn't glamorous from the outside. Only the row of European flags hints that something special goes on within.
The seven pixels that have excited people are from the enigmatic asteroid Lutetia, a hunk of space rock about the size of Majorca.
Until this Friday afternoon on 9 July, it had been just a single point of light in the spacecraft's navigation camera, indistinguishable from the distant stars. Now it is clearly getting bigger. In 24 hours time, the Rosetta spacecraft will race past Lutetia and attempt to send back the first close-up images.
The control room is a cross between the Starship Enterprise and a goldfish bowl. Banks of computer screens line the desks, a horseshoe shape around a central island of more screens. From the ceiling hang large digital clocks, one showing "universal time" – GMT to you and me – another showing the countdown to "closest approach", when a mere 3,000 kilometres will separate spacecraft from asteroid. The wall onto the corridor is glass so that passers-by can watch. Although everything appears calm, there is an undercurrent. People are sipping drinks just a little too quickly, nodding in vigorous agreement, as if anxious to disengage and return to their own responsibilities.
The only person who appears genuinely laid back is the one who should be feeling the pressure the most: Rita Schulz. A motorbike enthusiast in her free time, in here it is her job to ensure that science flows from the mission. Schulz is the first female project scientist at ESA and believes the agency would be "more healthy" if there were more women scientists.
She took over from Gerhard Schwehm. Avuncular with a wide smile, Schwehm is revered within the agency. He helped shepherd ESA's Giotto spacecraft to Halley's comet in 1986, when even the mighty NASA failed in this feat of celestial navigation. The success made ESA a world player in space exploration. On the day Giotto launched, some 25 years ago, Schwehm and his colleagues began planning Rosetta. Now edging towards retirement, he is the mission manager.
I hear Schulz's infectious laugh before I see her. Perched on the end of a desk with her laptop, she certainly doesn't seem like someone approaching a professional watershed. Dressed in multiple sleeveless T-shirts and sandals, she looks like she's on holiday. "Tomorrow I'll be nervous," she says, as if she can turn her emotions on and off at will.
Across the corridor, a cleaner is vacuuming the hall where Schulz will present either triumphant results or excuses for failure at a press conference scheduled for 23:00 the following night. A 15-foot-wide scale model of the Rosetta spacecraft, its solar panels extended like eagle wings, hangs above the dais.
Saturday night will be science on the fly – literally and metaphorically. When Rosetta launched in 2004 they had no objectives apart from a rendezvous with a distant comet in 2014. There was nothing of significance to visit in between because a delay in their launch date had robbed them of their intended targets. Only when the mission was safely in space, did the flight team look for things to do along the way.
To justify the $1bn (£650,000) European mission, it was always intended to fly past an asteroid or two en route. Having passed by a disappointing minnow, asteroid Steins in 2008, the flight team manoeuvred Rosetta towards Lutetia, one of the biggest mysteries in the asteroid belt. The asteroid hides its composition from us. It is expected to be a giant rock left over from the formation of the Earth and the other planets. But recently there has been a hint from ground-based telescopes that it could be a fragment of a shattered planet, a small world that was trying to grow alongside Earth but was blasted back into smithereens – our lost neighbour in space. If so, it will be made of metal rather than rock. And discovering more about asteroids is becoming increasingly important, and we could be seeing a lot more of them in coming years. Both NASA and ESA now believe sending astronauts to the Moon and Mars is too expensive. So they are fixing their sights on launching humans to nearby asteroids instead, which are easier to land on. Rosetta's 3,000-kilometre Lutetia encounter provides vital 'ground truth'.
As well as being scientifically invaluable, asteroids are probably the most accessible sources of minerals and precious metals beyond Earth – making them financially attractive too.
By Saturday morning the main camera has returned its first picture. Taken from a distance of 2 million kilometres, it clearly shows an irregular body: wedge-shaped, with two darker regions on its bulk. At the top there is a distinct curve that could be the lip of a crater. "This look promising," says Schwehm, grinning widely, "We can already make some guesses about Lutetia."
The flight team remains anxious. In the run-up to the Steins flyby, the camera malfunctioned, leaving them seven hours to diagnose and fix the problem. Eventually discovering that the camera was overheating, they compensated and the flyby was a success. They know how to avoid a reoccurrence, but they are tense.
"We're about to do the flip," says one of the controllers at lunchtime. The "flip" is a gradual roll of the spacecraft to prepare it for the flyby. I follow him to the screen, where there is a mosaic of four graphs. After a few seconds, the horizontal green lines begin to snake. He beams at me like a proud father. This is the flip. I hide my disappointment. Then it hits me. "You can picture the spacecraft from this, can't you?"
In reply, he holds up a clenched fist and extends little finger and thumb as if imitating a telephone. His fingers are the solar panels though, and his fist the bulk of the 3x2x2-metre spacecraft.
"It's doing this," he says watching the graphs and gently rolling his fist. The flip itself might not have been spectacular, but his mental connection to Rosetta was astonishing.
Schulz is dressed in a business suit today. She still looks calm, I venture.
"Not today," she says, nervously laughing, "Not today."
At 16:45, the flight team transfers control to the spacecraft's on-board computers. Now Rosetta is its own master, tracking the asteroid with its software and turning to keep Lutetia centred in its camera.
It means a nerve-wracking temporary loss of contact with the spacecraft at closest approach because, as Rosetta tracks, the main antenna will drift away from Earth. The data will be recorded for transmission. When the 40-minute blackout arrives, it becomes a vigil.
Just as Andrea Accomazzo, the spacecraft operations manager, is cautioning that it might take longer to re-acquire the signal, a heart- stopping alarm sounds. The flight team strain forwards in their seats. Rosetta is back online and the downloading begins.
The 10-strong camera team crowd their laptops, eager for the images. There are no American whoops or high-fives, just wide smiles of achievement passing among the team members as they study the black-and-white shots. The highly contoured surface is covered in craters of all sizes, indicating that Lutetia has suffered a remarkably violent past. One crater sprawls across half the length of the asteroid. Boulders litter the surface and there is an apparent landslide in the bottom of another crater.
On one image, the camera has captured not just the asteroid but Saturn in the background, its rings clearly visible.
Schulz and Schwehm watch as the team hurriedly prepare the images for presentation. Then they rush over to the waiting press, eager to show off the triumph. Amid multiple bouts of spontaneous applause, the question is raised: is asteroid Lutetia a rocky leftover or a shattered fragment?
Schulz explains that the necessary data is still onboard the spacecraft, to be downloaded during the next fortnight. Tonight is all about the images, but she says, "We've given ourselves a deadline of September to understand this asteroid." Although remarkably calm, I suspect she is quietly revelling in the moment of her first major scientific achievement as project scientist. Now she has cachet.
As for Rosetta, it will hunker down and hibernate for a few years until it reaches its main target: the icy comet Churyumov-Gerasimenko. Back at the beginning of the solar system, 4.5bn years ago, such objects could have delivered the water to Earth's oceans and the chemicals that became life on our world.
Rosetta will rendezvous with the comet and deploy a lander to its surface to perform in situ measurements of the ice and its chemical cargo. Whereas Saturday's flyby was about unlocking the formation of the Earth, in 2014 Rosetta will be looking for clues to the very origin of life.
'The Big Questions: The Universe' is published by Quercus (£12.99). To order a copy for the special price of £11.69 (free P&P) call Independent Books Direct on 08430 600 030, or visit www.independentbooksdirect.co.uk
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