[Spice_discussion] Ask for help about IAU_MOON

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Hi, Pro.Bachman
   I'a Chinese student, and nowadays I'm doing some calculation using SPICE to simulate position determination on the lunar surface.
   I've read through the SPICE tutorials and found there are three types of body-fixed system for the moon, which are MOON_PA, MOON_ME, and the IAU_MOON. According to the tutorials, IAU_MOON is said to be a bad choice for navigation on the lunar surface.
   I've found the definition for MOON_PA and MOON_ME in the paper "Report of the IAU/IAG Working Group on cartographic coordinates and rotational elements:2006" written by Seidelmann,which is in the section "3.Coordinate system for the moon". But I failed to find the definition for IAU_MOON.
   I would very like to appreciate you if you can help me with the following question:
   Is IAU_MOON definited as the planets orientation model which is described in "2.Definition of rotational elements for planets and satellites" of the paper abover?
   Why does IAU_MOON has a lower accuracy than MOON_PA and MOON_ME?

   Thank you very much!
   Hope to hear from you soon!

Sincerely, Hao Wanhong
Shanghai Astronomical Observatory, Chinese Academy of Sciences
wanhong.hao at gmail.com
2009-12-11