Launch

Accommodation of the EuroMoon 2000 spacecraft within the Ariane-4 fairing

A dedicated Ariane-4 launch to Lunar Transfer Orbit (LTO) allows adequate mass and fuel margins (including fuel for a hovering phase) to be included, a significant useful payload to be landed (including any dedicated support equipment, e.g. deployment devices), and a more structured mission to be conceived (leaving room for a piggyback Orbiter and hard-landing probes). The use of an Ariane-44LP (2910 kg to LTO) is assumed, although the more powerful 44L version (3470 kg to LTO) would provide even greater margins.

There is one launch opportunity available each day throughout the year and no seasonal launch-window restrictions, although illumination at the South Pole varies between summer and winter (±1.5°). This means that some slippage in launch date, to late-2000, could be accommodated and that the landing and surface operations could occur at any time of the year (the least favourable being local winter, for Sun visibility, and the most favourable the local summer, with the solstice in April 2001).

Transfer Orbit
The Ariane vehicle would launch the spacecraft into Lunar Transfer Orbit (LTO). After a small mid-course manoeuvre about one day after launch, insertion into the 200 km circular polar orbit would take place 4 6 days later. The direction of the Sun depends on the launch date, with a period of a lunar month. A dawn/dusk orbit is preferred, as it presents a more benign thermal environment than a noon/midnight orbit. Good surface illumination conditions can be obtained by waiting up to half a lunar day.

Lunar Orbit
Remote-sensing data will be acquired whilst in lunar orbit, both for operational needs (i.e. the data necessary to achieve a safe and useful landing) and for scientific purposes. The MORO payload has been adopted as a baseline, including:

• High-Resolution Imaging: The DLR/Dornier HRSC (High-Resolution Stereo Camera), for example, has a spatial resolution (stereo) of 4 8 m from 100 km, making imaging of the near-polar landing site possible from every orbital pass.

• Gravity Field (Subsatellite) Determination: Further analysis is needed to determine how crucial the improvement in the gravitational model made possible by conducting a dedicated subsatellite experiment would be. The Gravity Experiment would also make the EuroMoon 2000 mission itself more attractive.

Additional remote-sensing payloads of scientific interest would include:

• Global Mapping: This would be carried out with the HRSC.

• Microwave Radar Instrument: This would be used for mapping and radiometry, but its ability to locate water- ice deposits with kilometre accuracy may also have some operational impact (redirection of surface operation exploratory targets).

• Infrared Mapping Spectrometer: This would be used for mineralogy studies.

• X-ray Fluorescence Spectrometer: This would be used for studies of elemental composition.