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This was followed in 1998 by the " Lunar Prospector " mission , whose instruments indicated the presence of excess hydrogen at the lunar poles , which is likely to have been caused by the presence of water ice in the upper few meters of the regolith within permanently shadowed craters .
 instrument: Lunar Prospector
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: media, plant, vehicle, astronomical object, time, disease, animal, location, person, organization, mythical figure, food, biology, geographical phenomenon, instrument, event 
Text: {0} 
Answer:
 instrument: Lunar Prospector