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  • Accurate Transformations Of Coordinates And Construction Of Observation Vector Of Lunar Satellite In The Wake Of IAU2000A Precession Nutation Model

    Paper number

    IAC-07-C1.4.01

    Author

    Prof. Manoranjan Sinha, Indian Institute of Technology, India

    Coauthor

    Mr. N.S. Gopinath, Indian Space Research Organisation (ISRO), ISAC, India

    Coauthor

    Mr. N. K. Malik, Indian Space Research Organisation (ISRO), India

    Year

    2007

    Abstract
    The IAU has introduced the International Celestial Reference System (ICRS), the Celestial Intermediate Pole (CIP) and the Celestial Ephemeris Origin (CEO) in order to be consistent with the improved accuracies currently achieved and expected in the future for transformation from ICRS to International Terrestrial Reference System (ITRS) and vice-versa. The astrometric definitions and methods remain similar to the earlier convention, i.e. the FK5 system, but the bases for the ICRS are different from that of FK5. Moreover, the ICRS has introduced a number of simplifications. The earlier reference system was fixed dynamically while the present reference system ICRS is fixed kinematically, i.e., the changes are from a dynamical to a kinematic defining motion.  Bright stars were used earlier as a reference source but in ICRS extragalactic reference sources have been added making it more precise. Moreover, a precessing equinox has been replaced by a more stable fiducial point. Thus the earlier reference system which was taken to be moving with time, the present one (ICRS) is independent of date. This paper describes the complete simulation and expressions for transformation from Geocentric Celestial Reference Frame (GCRF) to topocentric reference frame (fixed to ground station) via ITRF which entails CEO and CIP for getting different observations. The expressions used are for use in the new transformation between the GCRS and the ITRS which is recommended by IAU resolution B1.8 which recommends that, beginning on 1 January 2003, the IAU 1976 precession model and IAU 1980 theory of nutation be replaced by the precession-nutation model IAU2000A. A comprehensive simulation has been carried out in the GCRF based on IAU2000A precession-nutation model using the CEO concept in the context of lunar satellite. Also a simulation based on the Equinox concept has been carried out making a comparative study with the CEO based results confirming the validity and accuracy of the results which differ very slightly. The new model provides explicit separation between precession-nutation of the equator from Earth rotation is more simple, compact and direct than the classical one, achieving accuracies at the level of a few micro arc seconds with greatly reduced scope for accidental misuse.
    Abstract document

    IAC-07-C1.4.01.pdf

    Manuscript document

    IAC-07-C1.4.01.pdf (🔒 authorized access only).

    To get the manuscript, please contact IAF Secretariat.