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1) National Astronomical Observatory, RISE 2) Iwate University

Technical Development of a Small Digital Telescope for In-situ Lunar Orientation Measurements (ILOM) .

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1) National Astronomical Observatory, RISE 2) Iwate University

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  1. Technical Development of a Small Digital Telescope for In-situ Lunar Orientation Measurements (ILOM) H. Hanada1, S. Tsuruta1, H. Araki1, S. Kashima1, K. Asari1, S. Tazawa1, H. Noda1, K. Matsumoto1, S. Sasaki1, K. Funazaki2, A. Satoh2, H. Taniguchi2, H. Kato2, M. Kikuchi2, Y. Itou2, K. Chiba2, K. Inaba2, N. Gouda3, T. Yano3, Y. Yamada4, Y. Niwa3, H. Kunimori5, N. Petrova6, A. Gusev6, J. Ping7, T. Iwata8S. Utsunomiya8, T. Kamiya8 & K. Heki9 1) National Astronomical Observatory, RISE 2) Iwate University 3) National Astronomical Observatory, JASMINE 4) Kyoto University 5) National Institute of Information and Communications Technology 6) Kazan Federal University 7) Beijing Astronomical Observatory, CAS 8) Japan Aerospace Exploration Agency 9) Hokkaido University

  2. PZT used in the International Latitude Observatory of Mizusawa (ILOM) Another observation independent of LLR is necessary

  3. Photographic Zenith Tube (PZT) Lens Photographic plate CCD array Tube (1/2 of the focal length) Mercury Pool Tilts of the tube are nearly cancelled (after Heki)

  4. Strategy of Development of a New PZT • Bread Board Model (BBM) : • Improvement of an accuracy • Environmental test of key elements. • in cooperation with Iwate University • Experimental Model (EM) : • Development of a PZT for observations of the Deflection • of the Vertical (DOV) related to Earthquakes and • volcanic eruptions (0.1 arc-seconds). • in cooperation with Shanghai Astronomical Observatory • Proto-Flight Model (PFM) • Development of a PZT for observations of Lunar rotation on the Moon (1 milli-arc-second)

  5. How the lunar core is ? (liquid or not ?) Outer Core (liquid) Core (liquid ?) Inner Core (solid) Earth Moon

  6. Principle of ILOM Observations Telescope Motion of a star in the view Other objectives than lunar rotation Pilot of lunar telescope （Engineering）　 Establishment of a lunar coordinate system

  7. 0.1m Development of BBM (Cooperation with Iwate univ.) Objective Motor 0.5m Frame Tube Mercury Pool Tiltmeter Tripod After Iwate Univ.

  8. Specification of the PZT

  9. Equipment for Centroid Experiment

  10. Artificial Star Images in Centroid Experiment

  11. An Algorithm for Centroid Experiment where : Real position : Photon weighted means We estimate the parameter k as well as the real positions

  12. Centroid Experiment Relative distance between two stars by linear correction of the photon-weighted mean. (Yano et al., 2004) The accuracy is about 1/300 pixel. (1 pixel : 20μm×20μm)

  13. Cover Glass Optical System of the PZT Objective Plane-parallel plate CCD Prism CCD window Cover glass for Mercury pool Mercury surface

  14. Relation between Temperature Change and Shift of the Center of Star Image (Conventional Objectives) Incident Angle Degree Shift of Star Image (mas) Temperature (℃） Temperature change of larger than 0.5 degrees is not allowed.

  15. Relation between Temperature Change and Shift of the Center of Star Image (Objectives with a Diffractive Lens) Incident Angle Shift of Star Image (mas) Degree Temperature (℃）

  16. Distinguish between the Real Displacement and the Artificial Ones From Patterns of Distribution Displacement due to thermal expansion etc. Initial Star position on CCD Displacement due to lunar rotation

  17. Concluding Remarks • We developed a BBM of PZT for observation of the deflection of the vertical and the lunar rotation. • Using BBM, we are doing performance tests of the driving mechanism and the optical system. • We succeeded in determination of star position with the accuracy of about 1/300 pixel, which corresponds to about 6 milli-arc-seconds for the PZT with 1m focal length and CCD of 20μm×20μm. • The attitude control system can make the tube vertical within an error of 0.006 degrees (or about 20 arc-seconds), which can be compensated by PZT to the positioning accuracy of 1 milli-arc-seconds.

  18. By introducing a diffraction lens, we can loosen thermal condition by about ten times compared with the case not introducing it, and temperature change of about 5 degree centigrade is permissible to realize the precision of the 1 milli-arc-seconds. • As to the shifts of star images due to thermal distortion of the optical elements, they can be approximated with a simple model and can be corrected for with the accuracy higher than 1 milli-arc-seconds except for that with a horizontal gradient. • We adopt a shallow copper shale for mercury pool of the Experimental Model, and confirmed that the effect of vibration is on the level of 0.1 arc-seconds.

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