Mission Instruments

The mission profile for all the three states involved launching of a satellite which would enter into a lunar orbit and position itself approximately around 100 km/200 km over the Moon’s surface. The sensors onboard of these satellites took various observations. The attempt was to analyse the composition of materials on and below the surface of the Moon. Idea was to know the physical properties of the Moon. Scientists wanted to know more about the terrain characteristics from the point of view of selecting future landing area for unmanned and manned missions. All this information was gathered without landing on the Moon, and the satellites were essentially used as remote sensing systems.

Japan’s Kaguya-1 mission had groupings of sensors meant for elemental distribu­tion, mineral distribution, surface and subsurface structure feature analyses, gaining environment knowledge and understanding gravitational field distribution.[239] China’s Chang’e-1 mission instruments could be roughly divided into mission groupings

like mineral distribution, Moon topography assessment and solar wind understand­ing, while India’s Chandrayaan-1 mission sensors were tasked to undertake terrain and mineralogy mapping of the Moon’s surface, look for availability of water on the Moon and understand more about lunar gravity. In a broader sense, there was much commonality in the missions of all the three states.

In the case of Kaguya-1 mission, the overall mission configuration was somewhat different from others. This Japanese mission constitutes not only of the orbiter but also two 50-kg small satellites (relay satellite and VRAD satellite: The relay satellite is known as Okina[240] and the other is Ouna) which were released by the main orbiter after it had reached lunar orbit. Relay satellite plays a role towards understanding the gravity field. Knowledge of gravity filed is essential to study the evolution of Moon. Here, four-way Doppler measurements of main orbiter by using relay satellite for far-side gravity field are taken.[241] [242] The other VRAD satellite (VLBI RADio source) contributes towards measurements transmission of radio waves which in turn contribute to the accuracy of the gravity field, especially on the lunar limb areas. The ground stations involved towards monitoring and processing the data received from the satellite include National Astronomical Observatory of Japan (NAOJ) and few others.11

The missions were also tasked to photograph the Earth form their position. It is expected that these missions would gather unknown information in regard to ionosphere and aurora.