Rosetta: The Complete Mission in Real-Time 3D
November 12, 2014
Experience the full Rosetta mission: follow the spacecraft's real ten-year journey across the Solar System to comet 67P/Churyumov-Gerasimenko, then Philae's landing on November 12, 2014, in a real-time 3D reconstruction.
It is March 2, 2004.
At Kourou, in French Guiana, an Ariane 5 is about to leave for a comet.
It carries Rosetta, a three-tonne European probe.
Its target: 67P/Churyumov-Gerasimenko, a comet four kilometres across.
The rendezvous will take place 400 million kilometres from Earth.
Far beyond the orbit of Mars, in the asteroid belt.
No probe has ever orbited a comet, nor landed on one.
Comets keep intact the matter that formed the Solar System.
Did they bring Earth its water, and the ingredients of life?
A mission of the European Space Agency, ESA: about 1.4 billion euros.
Liftoff. Two solid boosters and a Vulcain engine lift 750 tonnes.
Rosetta was to leave a year earlier, for another comet, Wirtanen.
The failure of another Ariane 5 flight grounded it. A new target was found.
At 66 kilometres up, the two spent solid boosters fall away.
The fairing opens at 106 kilometres: Rosetta sees space for the first time.
The main stage falls away. The upper stage carries Rosetta alone.
Usually, the last stage lights straight after separation.
Here it drifted nearly two hours, to fire at the right point of the orbit.
A quarter of an hour of thrust, and Rosetta escapes Earth, at 37,500 km/h.
Separation, 1,360 kilometres above Earth. Rosetta is alone.
Well, not quite: it carries Philae, clamped to its side.
Philae is a lander: once at the comet, Rosetta will release it to set down there.
Ahead of it, ten years of travel and 6.4 billion kilometres.
Rosetta unfolds its solar panels: 32 metres across.
They must power it farther from the Sun than any probe before it.
It is flown from ESA's mission control centre, in Darmstadt, Germany.
Free of Earth, Rosetta now circles the Sun, like a planet.
Six months after leaving, Rosetta is 76 million kilometres from Earth.
It is barely farther from the Sun than we are: its one-year loop brings it back.
No rocket can send it straight to the comet: it lacks the speed.
So it will come back and skim Earth, which will lend it some of its own speed.
Four slingshots in all: three times Earth, once Mars.
The point is not to pass 67P, but to fly alongside it, then orbit it.
In 1986, Europe's Giotto probe passed Halley's comet at 68 km per second.
On board, eleven science instruments. Philae carries ten more.
Its name comes from the Rosetta Stone, which unlocked the hieroglyphs.
Philae owes its own to a Nile island, whose obelisk helped read them.
Rosetta and Earth each go once around the Sun, to meet again at the same point.
4 March 2005. A year after leaving, Rosetta falls back towards Earth.
A year of flight has gained it nothing: it comes back at the speed it left with.
But Earth's gravity will bend its path and speed it up.
Not a drop of fuel: it is Earth that hands over a little of its speed.
At closest approach, 1,954 kilometres above the Pacific.
On the way past, Rosetta tests its instruments on Earth and the Moon.
Its speed relative to the Sun goes from 107,000 to 122,000 km/h: Earth has given it 15,000.
In exchange, Earth slows down: in a year, it falls behind by less than an atom.
Faster now, Rosetta swings farther from the Sun: its orbit crosses that of Mars.
February 2007. Rosetta dives towards Mars, its only flyby of another planet.
The riskiest flyby of the journey: it passes 250 kilometres above the ground.
On the night side, Rosetta enters the shadow of Mars: 25 minutes without sun.
Its batteries, never meant for so long an eclipse, have to hold.
At closest approach, at 36,000 km/h.
Mars sends Rosetta back towards Earth.
On the way past, Philae photographed Mars, with a Rosetta panel in the foreground.
Twice more, Earth lends it speed: in 2007, then in 2009.
Its new orbit carries it out to 790 million kilometres from the Sun.
So far out, its panels no longer suffice: Rosetta goes to sleep for 31 months.
20 January 2014: Rosetta wakes up, 9 million kilometres from 67P.
August 2014. After ten years on the road, 67P swells ahead of Rosetta.
Its nucleus has a shape nobody expected: two lobes, like a duck.
It is barely four kilometres across, and turns on itself in twelve hours.
The comet races along at 55,000 km/h. Rosetta now flies at the same speed.
6 August 2014, at 100 kilometres: for the first time, a probe escorts a comet.
In 1969, Klim Churyumov spots it on a photographic plate taken by Svetlana Gerasimenko.
It bears both their names. “67P” means the 67th periodic comet catalogued.
No orbit yet: Rosetta flies triangles in front of the comet, at 100 then 50 km.
On 10 September it enters orbit at 30 km, then steps down closer.
15 October 2014. Rosetta drops to less than 10 kilometres above the ground.
Its gravity is so weak that Rosetta circles it slower than walking pace.
Its camera picks out details twenty centimetres across.
A spot must be chosen for Philae: ground flat enough, lit, within radio reach.
In mid-September, ESA picks site J, on the small lobe.
But nobody knows whether this ground is hard as ice or soft as snow.
Heated by the Sun, the comet's ice turns into gas and dust.
As early as June, Rosetta measured it losing a glass of water every second.
Late October, Rosetta climbs back: Philae will be released 22 km from the nucleus's centre.
12 November 2014. Site J is now called Agilkia, a Nile island.
Philae: 100 kilos, three feet, ten instruments, and a battery for 60 hours.
Last night, its gas thruster refused to arm. It is released all the same.
Without it, nothing will press Philae down on contact. Its two harpoons remain.
A signal takes 28 minutes to reach Earth: it will all happen alone.
Release. Philae drifts away at 19 centimetres per second and unfolds its feet.
It has no engine to steer with: its fall was calculated in advance.
Philae is the work of a European consortium, led by Germany and France.
It is from here, moving away, that Philae photographed Rosetta.
Seven hours of falling, in gravity a hundred thousand times weaker than Earth's.
During the descent, its instruments already measure the dust and the gas.
Below it, the comet turns: it has to aim at ground that is moving.
Twenty minutes to contact. Philae arrives at walking pace, one metre per second.
Contact. For the first time, a spacecraft touches the surface of a comet.
The harpoons were meant to anchor it. Nothing holds it down: it bounces.
On Earth, they must wait: the signal takes 28 minutes to cross 510 million km.
5:03 pm in Darmstadt: its feet did touch the ground. The room applauds.
But the harpoons never fired, and its panels show it spinning: it has lifted off again.
It climbs back up nearly a kilometre, and flies for almost two hours.
Below it, the comet has turned: it will not land where it touched.
It comes down farther away, then makes another hop of a few minutes.
Philae stops at Abydos, against a cliff, one foot in the air.
That evening, its magnetometer confirms it: Philae touched the comet three times.
Rosetta drops below its horizon: no contact until the next morning.
Philae sends radio waves to Rosetta, straight through the comet's head.
How they pass reveals it: the inside is porous, three quarters empty space.
13 November. Its first photo arrives: a wall of rock, a few metres away.
Stuck in shadow, it sees the Sun for only an hour and a half a day.
Its panels recharge almost nothing: it is living on its battery alone.
The team changes plan: run all ten instruments while the power lasts.
Its hammer strikes the ground at full power. It goes in only a few millimetres.
Under twenty centimetres of dust, ice far harder than expected.
14 November. The drill goes down, but no one knows if it reaches the ground.
Philae is not anchored: in ground this hard, drilling could push it away.
One last manoeuvre: its body turns 35° to hold its panels up to the Sun.
15 November, just past midnight. The last data come in, then the battery gives out.
Philae falls asleep. All ten instruments have worked. No one knows where it is.
Rosetta photographs the area: five Philae-sized specks. None of them is it.
The radar link narrows the area to a strip 16 m by 160. Philae stays out of sight.
March 2015. The comet nears the Sun: Rosetta starts listening.
With Rosetta alongside, the comet falls towards the Sun and crosses the orbit of Mars.
13 June 2015, 10:28 pm in Darmstadt. A signal: Philae is alive.
85 seconds of data. It is -35 °C on board, with 24 watts to spare.
8,000 packets in its memory: it had been awake for days, unable to call.
Seven more contacts follow, too short and unstable to start a measurement.
One transmitter and one receiver seem dead, and the other transmitter cuts out.
Rosetta would like to move closer to hear it better, but the dust keeps it away.
9 July 2015: the last signal. After that, Philae falls silent for good.
30 July 2015: its results come out. Sixteen organic molecules, four never seen before.
13 August 2015. The comet passes closest to the Sun: 186 million kilometres.
Its ice does not melt: heated, it turns straight into gas.
But that ice is not at the surface: it lies under a crust of black dust.
The gas escapes through collapsed pits, some of them two hundred metres deep.
Each area wakes at its own sunrise, and goes out at its own sunset.
It loses three hundred kilos of water a second, a thousand times its 2014 rate.
Pushed by the Sun's light, the dust streams out behind it into a long tail.
Rosetta had to back off: in that dust, its star trackers lost the sky.
Past the Sun, the comet heads back into the cold, and its activity slowly fades.
January 2016. A last command: spin up its flywheel to shake off the dust.
The command goes out. No answer.
27 July 2016: to save power, Rosetta stops listening for Philae.
2 September 2016. In a photo taken from 2.7 km, Rosetta finally finds it.
On its side, wedged in a dark crack: that is why it could barely talk.
Twenty-two months of searching. Four weeks later, the mission ends.
September 2016: the comet is farther from the Sun than when Rosetta arrived.
Too far from the Sun for its panels, Rosetta will end its mission on the comet.
It descends slowly towards the ground, photographing everything to the last.
The water of 67P is different from that of Earth's oceans.
So Earth's water does not mostly come from comets like 67P.
Rosetta also detected glycine, an amino acid, and phosphorus.
Ingredients of life, kept intact since the birth of the Solar System.
On contact, Rosetta falls silent, twelve and a half years after leaving Kourou.
Rosetta and Philae stay on the comet, which carries them around the Sun.
Never before had a human-made craft landed on a comet. ESA's teams achieved this feat.