H. Hanada 1, S. Tsuruta 1, H. Araki 1, S. Kashima 1, K. Asari 1, S. Tazawa 1, H. Noda 1, K. Matsumoto 1, S. Sasaki 1, K. Funazaki 2, A. Satoh 2, H. Taniguchi 2, H. Kato 2, M. Kikuchi 2, Y. Itou 2, K. Chiba 2, K. Inaba 2, N. Gouda 3, T. Yano 3, Y. Yamada 4, Y. Niwa 3, H. Kunimori 5, N. Petrova 6, A. Gusev 6, J. Ping 7, T. Iwata 8 S. Utsunomiya 8, T. Kamiya 8 & K. Heki 9 Technical Development of a Small Digital Telescope for In-situ Lunar Orientation Measurements (ILOM) 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

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

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

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) Strategy of Development of a New PZT

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

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

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

Specification of the PZT Aperture0.1m Focal Length1m TypePZT DetectorCCD Pixel Size5μm×5μm (1″×1″) Number of pixels4,096×4,096 View1°× 1° Exposure Time40s Star MagnitudeM < 12 Accuracy 1/1,000 of pixel size (1mas)

Equipment for Centroid Experiment

Artificial Star Images in Centroid Experiment

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

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

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

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

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

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

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 degrees (or about 20 arc-seconds), which can be compensated by PZT to the positioning accuracy of 1 milli-arc- seconds.

 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.