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Planetary News: SMART-1 (2004)

SMART-1 Reaches the Moon

By Emily Lakdawalla
16 November 2004
SMART-1
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Little SMART-1 fires its engine to achieve capture into lunar orbit Credit: ESA

The European Space Agency's plucky SMART-1 spacecraft has finally achieved lunar orbit. "This is something that every European should be extremely proud of," stated David Southwood, ESA's Director of Science. "Little SMART-1 has had quite a battle." The spacecraft, which was intended to demonstrate miniaturized technologies and solar electric propulsion, traveled nearly 90 million kilometers (50 million miles) over thirteen months in her journey from the Earth to the Moon.

The journey of SMART-1 took her on an ever-widening spiral around the Earth as she used the tiny thrust of her solar electric engine to push her orbit higher and higher. By her 331st orbit, on November 11, she had reached a position in the Earth-Moon system that was just balanced between the gravitational fields of the two bodies. This position, termed a "weak stability boundary," is a no-man's land where the motions of the spacecraft are very difficult to predict. Octavio Camino, SMART-1's Mission Control Manager, was full of praise for the ESA avionics team who were able to guide SMART-1 across this region and down into lunar orbit.

"This has been very demanding in terms of navigation. This mission is really an achievement for flight dynamics and mission analysis," Camino said. "It has been an achievement for the flight dynamics capability of ESA. We have developed new algorithms and new tools that we can use in the future. We have achieved the target of getting to the Moon. ESA is now ready to take on future missions."

The reason that SMART-1's journey has taken so long is that her solar electric engine, unlike traditional chemical engines, is not capable of high-powered thrust. Over 3648 total hours of operation, SMART-1's engine has imparted about 2700 meters per second (6100 miles per hour) to the spacecraft. (By comparison, chemical engines can change the velocity of spacecraft by several hundred meters per second in operation times measured in minutes.) But SMART-1 has accomplished that change in speed with remarkable efficiency. To get to the Moon she expended only about 60 kilograms (130 pounds) of xenon propellant. "That is about 2 million kilometers per liter [5 million miles per gallon]," remarked Giorgio Saccocia, Head of the Propulsion Division at ESA's European Space Technology Centre. "I would like that fuel efficiency for my car!"

As a technology demonstration mission, SMART-1 is now a complete success for ESA. And with the first lunar orbit underway, the mission's scientists are ready to deploy their suite of miniaturized instruments. Bernard Foing, SMART-1's project scientist, spoke like a proud father about his spacecraft. "Our baby, SMART-1, is very special," he said. "It is equipped with three eyes: one in the visible, one infrared spectrometer, and one x-ray spectrometer. It has also three noses. Two of them are quite long. Through them we can smell the particles in the environment...."

While in the "weak stability boundary" region, Foing reported, SMART-1 achieved another milestone: the first imaging of the lunar North Pole, and parts of the far side, by a European spacecraft. Europe is the fourth space agency to achieve farside imaging (after the Soviet Union, the United States, and Japan), and the second to see the North Pole. But "we are getting there," he said. "Europe is getting there to planetary exploration."

The north pole of the Moon as seen by SMART-1
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The north pole of the Moon as seen by SMART-1
Captured from a distance of 60,000 kilometers on November 12, 2004, this photo represents the first glimpse of the lunar farside by a European spacecraft. As seen from Earth, the Moon was just about at new phase, but SMART-1 peeked over the North Pole to glimpse the lunar farside. Credit: ESA / Space-X, Space Exploration Institute

In fact, that is the real significance of SMART-1's lunar orbit insertion: this event, along with the successful arrival of Mars Express last summer, represent Europe's arrival into the select club of spaceborne planetary explorers. "Everybody is going to the Moon," Southwood said, acknowledging the plans of a host of nations to visit the Moon in the coming years. "But the Moon is only a step to the rest of our solar system. We're already, every day, at Mars. We are on our way to two asteroids and a comet, with the Rosetta mission, and a year from now we'll be on our way to Venus. A few years after that, using the technologies we have proved here with SMART-1, we'll be on our way to Mercury. Of course the other big event to come is early next year, we will land on a moon of Saturn, Titan. So these are great times for solar system exploration, and it's great to have Europe up there, playing a front ranked role."

What Europe accomplishes next, Southwood said, is a matter of the political will of its citizens. "The big question for Europeans, is ‘what is our role in space exploration?'" he asked. "Are we going to send humans in the future? Today, with our first ‘small genius' arriving at the moon, these questions should go through our minds. This is the beginning of something, but what exactly is it? We've given you the access to the solar system: what are we going to do? Are we going to explore it?" The Planetary Society, for one, hopes that Europe will take up Southwood's challenge.