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ESA’s SMART-1 Delivered New Image of lunar South-Polar Region

Newly-released images of the lunar south-polar region obtained by ESA’s SMART-1 are proving to be wonderful tools to zero-in on suitable study sites for potential future lunar exploration missions.

SMART-1’s Advanced Moon Imaging Experiment (AMIE) has collected many images of the lunar south-polar region, with unprecedented spatial resolution. The images, obtained over a full year of changing seasons were used to study the different levels of solar illumination on the Moon’s surface.

The orientation of the lunar rotation axis is such that the Sun just about grazes the lunar poles, leaving some regions permanently shadowed.

Shackleton crater is located in the inner ring of the south pole Aitken basin, the largest known impact basin in the solar system. It has a diameter of 2600 km.

The south pole is located on the rim of Shackleton crater. SMART-1 took images around the crater, which is a strong contender for a future robotic and human exploration site and for a permanent human base.

The polar mosaics show geological features of interest within reach from the south pole. Monitoring of the illumination of selected polar sites has allowed scientists to confirm that a ridge located 10 km from the Shackleton rim is prominently illuminated, and could be a strong contender for a potential future lunar outpost.

The large number of impact craters in the area indicates that the terrain is ancient. An example is crater Amundsen, 105 km in diameter, lying 100 km from the pole. It shows central peaks and asymmetric terraces that deserve geological and geochemistry studies.

The Lunar Prospector mission had previously indicated evidence of enhanced hydrogen in the permanent shadowed floors of polar craters, possible sign of water ice – a relevant element when choosing a human outpost.

As to whether or not ice could still be trapped under the floor of polar craters, the former SMART-1 Project Scientist Bernard Foing said, “To understand whether or not water is possibly present at the south pole, we have to take into account the following factors: how volatile elements were delivered to the lunar surface by comets or water-rich asteroids, whether they were destroyed or persisted under a dust cover and for how long they were able to accumulate.”

“The polar regions are still lunar incognita, and it is critical to explore them and study their geological history,” he added.

Using SMART-1 images, SMART-1 AMIE investigators and US collaborators have also counted small impact craters on Shackleton ejecta blanket to estimate the age of the crater. They have found that the number of craters is twice that of Apollo 15 landing site, which would make the Shackleton crater between 3.9 to 4.3 thousand million years old.

“Previous investigators believed Shackleton to be much younger, but that could be due to grazing illumination at the poles, which enhances the topography, mimicking a younger crater.”

So, in view of SMART-1 observations, the south polar site looks even more interesting with the confirmation of prominently-lit sites, and the indication of old craters where ice could have had more time to accumulate in permanently-shadowed areas.

“The SMART-1 south polar maps indicate very exciting targets for science and future exploration, within travel reach from a rover or humans at the south pole”, says Jean-Luc Josset, Principal Investigator for the AMIE.

About SMART-1
Smart1 was a Swedish-designed European Space Agency satellite that orbited around the Moon. It was launched on 27 September 2003 at 23:14 UTC from the Guiana Space Centre in Kourou, French Guiana. "SMART" stands for Small Missions for Advanced Research in Technology. On September 3, 2006 (05:42 UTC), SMART-1 was deliberately crashed into the Moon's surface, ending its mission.

SMART-1 was about one metre (approximately 3 feet) across, and lightweight in comparison to other probes. Its launch mass was 367 kg or 809 pounds, of which 287 kg (633 lb) was non-propellant.

It was propelled by a solar-powered Hall effect thruster (Snecma PPS-1350-G) using xenon propellant, of which there was 82 kg (50 litres by volume at a pressure of 150 bar) at launch. The thrusters used an electrostatic field to ionize the xenon and accelerate the ions to a high speed. This ion engine setup achieved a specific impulse of 16.1 kN·s/kg (1,640 seconds), more than three times the maximum for chemical rockets. Therefore 1 kg of propellant (1/350 to 1/300 of the total mass of the spacecraft) produced a delta-v of about 45 m/s. The thruster had a weight of 29 kg with a peak power consumption of 1,200 watts.

The solar arrays made 1,190 W available for powering the thruster, giving a nominal thrust of 68 mN, hence an acceleration of 0.2 mm/s² or 0.7 m/s per hour (i.e., just under 0.00002 g of acceleration). As for all ion-engine powered craft, orbital maneuvers were not carried out in short bursts but very gradually. The particular trajectory taken by SMART-1 to the Moon required thrusting for about one third to one half of every orbit. When spiralling away from the Earth thrusting was done on the perigee part of the orbit. The total delta-v expected over the thrusting lifetime of 5,000 hours is about 4 km/s, corresponding to a total impulse of 1.5 MN·s.

As part of the European Space Agency's strategy to build very inexpensive and relatively small spaceships, the total cost of SMART-1 was a relatively small 110 million euros (about 126 million U.S. dollars).

SMART-1 was designed and developed by the Swedish Space Corporation on behalf of ESA. Assembly of the spacecraft was carried out by Saab Space in Linköping. Tests of the spacecraft were directed by Swedish Space Corporation and executed by Saab Space.

The project manager at ESA was Giuseppe Racca and the project mananger at the Swedish Space Corporation was Peter Rathsman.

As a part of Small Missions for Advanced Research in Technology, SMART-1 tested new spacecraft technologies. The primary objective of SMART-1 was to test the solar-powered ion thruster. A secondary objective was to gather more information about the Moon, such as how it was created. SMART-1 mapped the lunar surface by way of X-ray and infrared imaging, taking images from several different angles so that the Moon's surface can be mapped in three dimensions. It also determined the Moon's chemical composition using X-ray spectroscopy. A specific goal was to use infrared light to search for frozen water at the Moon's south pole, where some areas of the surface are never exposed to direct sunlight. SMART-1 also mapped the Moon's Peaks of Eternal Light (PELs), mountaintops which are permanently bathed in sunlight and surrounded by craters shaded in eternal darkness. SMART-1 also tested the use of miniaturized scientific instruments, which are considered more efficient.

SMART-1 ended its mission by being deliberately crashed onto the Moon's surface at 34.24° S 46.12° W. Scientists hope that the impact will have kicked up a large enough quantity of fresh lunar "soil" so that they may study its composition.

About European Space Agency
The European Space Agency (ESA), established in 1974, is an intergovernmental organisation dedicated to the exploration of space, currently with 17 member states. Headquartered in Paris, ESA has a staff of about 1,900 with an annual budget of about €2.9 billion in 2007.

ESA's main spaceport is Guiana Space Centre in Kourou, French Guiana (French terretory). It is close to the equator, hence commercially important orbits are easier to access.[citation needed] ESA became the market leader in commercial space launches in the 1990s. In recent years, ESA has also established itself as a major player in space exploration.[citation needed]

ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, and the European Astronauts Centre (EAC), that trains astronauts for future missions is situated in Cologne, Germany.

ESA has ambitious space plans that may be divided into three large categories. First, ESA will maintain its scientific and research projects (e.g. tests and developments of new propulsion systems), try to find ways to reduce costs for their rocket fleet while enhancing their capacities, honour its commitments regarding the ISS and engage in further space exploration like the Venus Express mission that was launched in late 2005. The second category has many parallels to NASA's plans and consists of astronomy-space missions such as the Planck Surveyor studying the cosmic microwave background (2008), the Herschel space observatory (2008), and the Darwin interferometer.

While the projects described above are more or less similar in their structure and aim as NASA's and other space agencies' plans, the ESA's Mars project is different. The Aurora Programme lays out a time table for future missions to Mars, however in contrast to NASA's plans there is no emphasis on manned or unmanned lunar missions, it rather includes several flagship missions designed to develop and test technology needed for a manned European Mars mission currently planned for 2030. Among these flagship missions is ExoMars, a mission involving a Mars rover. Until 2005 ExoMars was planned to be a joint mission between NASA and ESA, however obstacles such as American technology law that prohibits sharing of classified space technology information led to ESA deciding to go for it alone. The mission is currently planned to launch in 2013. An even more ambitious Mars project is the Mars Sample Return Mission, that is planned as a follow-up mission to ExoMars. It will involve the first time a probe will return of samples from another planet, making it necessary to construct an ascent module that is capable of starting into Mars orbit and dock with the original probe.

Among the actions for returning the investment to society, they have developed the SCOS 2000 satellite control centre, and they allow the use of it free of charge to any European firm.

To increase the human value of the participating countries, ESA also develops collaborative training programs for students, young graduates and Post Doctorals. Some countries have their own bilateral agreements with ESA like the Portuguese trainees or the Spanish Trainees programs. The return of the trainees to their respective country aims to stimulate their national space industry.

In figure 1, Lunar south pole mosaic

In figure 2, Lunar south pole mosaic - annotated