/ 16 November 2004

High-tech European probe reaches moon

Europe’s first mission to the moon, the unmanned exploratory probe Smart-1, has been safely placed in lunar orbit after a voyage of more than 13 months, the European Space Agency (ESA) announced on Tuesday.

Smart-1, a tiny test-bed of revolutionary technology, was successfully captured by the moon’s gravity on Monday, ESA’s director of science, David Southwood, said in a teleconference from mission control in Darmstadt, western Germany.

“Our small genius is … at the moon,” a delighted Southwood declared.

The probe achieved lunar orbit at 5.53pm GMT on Monday, and on Tuesday was looping the moon at a height of 5 000km to 6 000km, Smart-1 project manager Giuseppe Racca said.

Smart-1 will gently spiral closer to the lunar surface, eventually stabilising in an egg-shaped polar orbit that will vary from 300km at the south pole to 3 000km at the north pole.

The 370kg probe has been using a slow but revolutionary form of propulsion, taking it in ever-widening circles around the Earth and using terrestrial gravity as a slingshot to get to the moon.

It is powered by an ion engine, which converts solar power into electricity that then charges atoms of the heavy gas xenon.

These charged atoms, known as ions, are then disgorged from the back of the probe to give it thrust.

Slow but efficient

The motor is initially slow — launched on September 27 2003, Smart-1 has taken more than 13 months to make a trip achieved in three days by the chemical rockets of the Apollo era — but speed gradually builds up in the frictionless environment of space.

Smart-1‘s motor has also been highly efficient. Since September, it had operated for more than 3 300 hours to cover 78-million kilometres and sipped just 52kg of its 80kg of xenon fuel.

By comparison, space rockets typically have tonnes of fuel.

“The performance [of the motor] has been better than we expected,” said Giorgio Saccoccia, head of ESA propulsion division, who added it will be ideal for long-range missions to Mercury — for which a European mission is planned in 2006 — as well as the Sun and the outer planets.

“We would certainly want to have it onboard in the future.”

It is only the second time that ion propulsion has been used as a space mission’s primary propulsion system. The first was Nasa’s Deep Space 1 probe, launched in October 1998.

Six months of scans

After achieving its final orbit on January 13 next year, Smart-1 will start a six-month scan of the moon, using a big payload of sensors that are also a test bench of miniaturisation.

One of the spacecraft’s tasks is to check out hopes that deep craters near the moon’s poles may harbour water ice, a discovery that would be a huge boost for setting up a human settlement.

It will also explore theories regarding the origin of the Moon.

The prevailing notion is that the moon was born from the Earth — a mass of terrestrial mantle that was smashed away when Earth was hit by a Mars-sized object in the infancy of the solar system.

This mass of rock and debris then recondensed to become Earth’s satellite, according to this theory.

“With our X-ray eyes, we want to trace the moon’s beginnings,” said Bernard Foing, Smart-1 project scientist.

Much is already known about the moon, thanks to robot craft and the manned United States missions of the early Sixties and Seventies, but scientists say there are also many unknowns.

Smart-1 is the first in a flotilla of unmanned probes to Earth’s companion. Missions have been planned in the coming years by China, India, Japan and the US.

“These are great times for space exploration,” said Southwood. “It’s great to have Europe up there, playing a front-rank role.” — AFP