Spiral to the Moon

ion engine
SMART ion engine.
Credit: ESA

SMART-1 captured its first close-range images of the Moon this January, during a sequence of test lunar observations from an altitude between 1000 and 5000 kilometers above the lunar surface.

SMART-1 entered its first orbit around the Moon on 15 November 2004. It has spent the two months following spiralling down to the Moon and testing its array of instruments.

The first four days after being captured by the lunar gravity were very critical. There had been the risk, being in an ‘unstable’ trajectory, of escaping the Moon’s orbit or crashing onto the surface. Because of this, the electric propulsion system (or ‘ion engine’) started a thrust to stabilize the capture.

The ion engine was switched on until 29 December, allowing SMART-1 to make ever-decreasing loops around the Moon. The engine was switched off between 29 December and 3 January 2005 to allow scientists to start observations. At this point, the AMIE camera took the close-up lunar images. The engine was switched off again to optimize fuel consumption on 12 January, and SMART-1 will spend until 9 February making a medium resolution survey of the Moon, taking advantage of the favorable illumination conditions.

ion engine
Mosaic of lunar images from SMART-1.
Credit: ESA

SMART-1 Project Scientist Bernard Foing said "A sequence of test lunar observations was done in January at distances between 1000 and 5000 kilometres altitude, when the electric propulsion was paused. We are conducting more survey test observations until the electric propulsion resumes from 9 February to spiral down further towards the Moon. SMART-1 will arrive on 28 February at the initial orbit with altitudes between 300 and 3000 kilometers to perform the first phase of nominal science observations for five months."

The first close-up image (lower right) shows an area at lunar latitude 75° North with impact craters of different sizes. At low illumination angles, the crater shadows allow scientists to derive the height of crater rims. "This image was the first proof that the AMIE camera is still working well in lunar orbit," says AMIE Principal Investigator Jean-Luc Josset of Space-X.

The composite images shown left were created to show larger-scale features. The first mosaic shows the complex impact crater Pythagoras and the strip of images (bottom) was produced from images taken consecutively along one orbit.

Starting with this mosaic, SMART-1 scientists expect to build up a global medium-resolution context map, where high-resolution images later observed from lower altitude can be integrated.

ion engine
Mosaic of lunar images from SMART-1. Moon image using AMIE’s clear filter
Credit: ESA

In April 2005 SMART-1 will begin the second phase of its mission, due to last at least six months and dedicated to the study of the Moon from a near polar orbit. For more than 40 years, the Moon has been visited by automated space probes and by nine manned expeditions, six of which landed on its surface. Nevertheless, much remains to be learnt about our closest neighbour, and SMART-1′s payload will conduct observations never performed before in such detail.

The Advanced/Moon Micro-Imaging Experiment (AMIE) miniaturized CCD camera will provide high-resolution and high-sensitivity imagery of the surface, even in poorly lit polar areas. The highly compact SIR infrared spectrometer will map lunar materials and look for water and carbon dioxide ice in permanently shadowed craters. The Demonstration Compact Imaging X-ray Spectrometer (D-CIXS) will provide the first global chemical map of the Moon and the X-ray Solar Monitor (XSM) will perform spectrometric observations of the Sun and provide calibration data to D-CIXS to compensate for solar variability.

The SPEDE experiment used to monitor Solar Electric Primary Propulsion interactions with the environment will also study how the solar wind affects the Moon.

The overall data collected by SMART-1 will provide new inputs for studies of the evolution of the Moon, its chemical composition and its geophysical processes, and also for comparative planetology in general.

Recent Lunar Timelines

- Japanese Hiten, Lunar Flyby and Orbiter
- Michael Rampino and Richard Strothers propose Earth could be periodically struck by comets dislodged from orbits when the solar system passes through galactic plane
- US Dept. Defense/NASA Clementine mission, Lunar Orbiter/Attempted Asteroid Flyby
- First commercial lunar mission, AsiaSat 3/HGS-1 , Lunar Flyby
- Lunar Prospector launches and enters lunar orbit
- Lunar Prospector tries to detect water on the Moon (polar impact)
- Lunar soil samples and computer models by Robin Canup and Erik Asphaug support impact origin of moon
- SMART 1, launched lunar orbiter and test solar-powered ion drive for deep space missions
- Japanese Lunar-A, Lunar Mapping Orbiter and Penetrator, to fire two bullets 3 meters into the lunar soil near Apollo 12 and 14 sites
- Japanese SELENE Lunar Orbiter and Lander, to probe the origin and evolution of the moon

Related Web Pages

Lunar Prospector
Impact origin of moon
Review of Theories of Moon-Forming Impact (Planetary Science Institute)