To capture the images, SMART-1 mission planners had to make sure that when the spacecraft aimed its camera at a particular lunar feature, there would be enough sunlight to illuminate the target.

That is no easy task when the spacecraft's five-hour orbit carried it around the Moon from mid-day to midnight in just a couple of hours. Not only that, but the SMART-1 team also had to ensure that the spacecraft surveyed as much of the Moon as possible during the mission.

"To decipher the formation and evolution of the Moon, and the processes that shape its landscapes, we needed both global coverage and dedicated observations of specific targets," said mission scientist Bernard Foing.

To accomplish this, planners used a number of innovative observing modes - four styles in all: nadir observations, targeted observations, moon-spot pointing and push-broom observations.

During SMART-1's first six months - the nominal mission - the emphasis was placed on surveying. Previously, the best digital Moon maps were produced by NASA's Clementine mission, which revealed color details as small as 200 meters (650 feet) across. At its best, SMART-1 maps reveal features only 40 meters (130 feet) across.

"SMART-1 has produced images for some very detailed maps of the Moon," said David Frew, SMART-1's science operations manager at ESA's European Space Research and Technology Center in The Netherlands.

To achieve the survey, the spacecraft simply pointed its cameras straight down and continuously recorded what passed beneath. Known as nadir observations, they were not as simple as they sound because of the Sun's heat on the spacecraft.

To keep SMART-1 cool, the spacecraft has a number of radiators on its side panels, which also hold star trackers. The tiny cameras watch the stars, so SMART-1's orientation and movement can be computed.

When sunlight falls onto these sides, however, the radiators cannot dissipate the excess heat efficiently and so the star trackers could stop working if direct sunlight heated them beyond a certain point. So the spacecraft has to twist during its orbit to keep the sunlight off the side panels.

This twisting motion turned the cameras and required the science team had to calculate image times carefully to ensure that the camera recorded every part of the lunar surface.

During the survey mode, the other science instruments were also recording data. For example, the X-ray instrument, D-CIXS collected nearly 10 full maps of the lunar surface.

The data will be combined into a single definitive map of the Moon's surface composition. It should help determine whether the Moon formed from the debris of a gigantic collision between the Earth and another planet-sized body during the early history of the solar system.

Toward the end of the six-month nominal mission, the team began to experiment with targeted observations. This involved tilting the spacecraft so it captured a lunar feature, even though the spacecraft did not pass directly over the top of it.

This was useful for making the most of the infrared spectrometer, SIR, because it has a small field of view just less than one kilometer across. It allowed SIR to measure mineralogical changes across the central peaks of lunar craters.

The targeted observations became increasingly important throughout the extended mission. The survey mode continued when no special targets where available.

During the northern winter phase of the extended mission, SMART-1's orbit carried it toward the dawn-dusk line, so targets directly below the spacecraft were poorly lit.

This meant tilting SMART-1 toward the sunlit lunar regions. "The illumination drives the way we observe with SMART-1," Frew said.

Targets were selected from requests made by the instrument science teams. Frew and SMART-1 science operations colleagues used computer simulations of SMART-1's orbit to determine whether the requested observations would be possible. Once they had identified a suitable opportunity to gather the data, the instructions were programmed into SMART-1.

Two types of targeted observation were possible. The simplest were when SMART-1 tilted slightly, so that the instruments would track over the feature.

Second were the moon-spot pointings. These were used to keep looking at a specific feature as SMART-1 flew past it. For the moon-spot pointings, SMART-1 had to turn to keep the target in sight.

Such observations enable scientists to understand the topography and surface roughness of lunar features, because they see them from different angles.

The science operations team also used push-broom observations. This technique allowed color images of the Moon to be made.

SMART-1's camera, AMIE, had been constructed so its light-collecting detector was split into four regions. One was clear and the other three had filters to cut out all but certain wavelengths of red and infrared light.

In the push-broom mode, the camera would take a continuous series of images with a carefully selected exposure time so the motion of the spacecraft resulted in the surface features falling into each filter one after the other.

This required keeping the camera pointed exactly in the direction of the spacecraft's orbit. Unless the team was careful, sunlight would hit the side panels containing the radiators and star trackers.

The team identified a number of times when, although sunlight would strike the panels, the heating remained within tolerable limits.

"The push-broom observations were entirely successful," said Miguel Almeida, a science operations engineer at ESTEC. Now scientists will be able to create contextual maps of surface minerals and, for instance, search for glassy areas on the lunar surface, betraying meteorite strikes that have melted small areas.

Scientist are now preparing for the final phase of the mission, a series of increasingly low altitude orbits that will provide the closest looks of the entire mission. Scientists want to study the lunar south pole in particular to see if there are any possible landing sites for future missions.

"When you get close, areas that look smooth are actually very rough," Almeida said.

"SMART-1 will help to pinpoint interesting and safe terrains for future exploration," Foing said. "We are using our data and operational experience to contribute to the next generation of international lunar orbiters and landers."

Eventually, the decreasing orbit will run SMART-1 into the Moon, ending the mission in a small impact that will leave behind just a small crater a few meters wide.

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