Transcript 月面環境評価 - Solar System

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. Iwata8 S.
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
PZT used in the International
Latitude Observatory of
Mizusawa (ILOM)
Another observation
independent of LLR is
necessary
Photographic Zenith Tube (PZT)
Lens
Tube (1/2 of the focal length)
Photographic
plate
CCD array
Mercury Pool
Tilts of the tube are nearly cancelled
(after Heki)
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)
How the lunar core is ? (liquid or not ?)
Outer Core (liquid)
Inner Core (solid)
Earth
Core (liquid ?)
Moon
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
0.1m
Development of BBM
Objective
(Cooperation with Iwate univ.)
Motor
0.5m
Frame
Tube
Mercury Pool
Tiltmeter
Tripod
After Iwate Univ.
Specification of the PZT
Aperture
Focal Length
Type
0.1m
1m
PZT
Detector
Pixel Size
Number of pixels
View
CCD
Exposure Time
Star Magnitude
Accuracy
5μm×5μm (1″×1″)
4,096×4,096
1°× 1°
40s
M < 12
1/1,000 of pixel size (1mas)
Equipment for Centroid
Experiment
Artificial Star Images in Centroid Experiment
An Algorithm for Centroid Experiment
where
: Real position
: Photon weighted means
We estimate the parameter k as well as the
real positions
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)
Optical System
of the PZT
Cover Glass
Objective
Plane-parallel plate
Prism
Cover glass for Mercury pool
Mercury surface
CCD
CCD window
Relation between Temperature Change and Shift
of the Center of Star Image
Shift of Star Image (mas)
(Conventional Objectives)
Incident Angle
Degree
Temperature (℃）
Temperature change of larger than 0.5 degrees is not allowed.
Relation between Temperature Change and Shift
of the Center of Star Image
Shift of Star Image (mas)
(Objectives with a Diffractive Lens)
Incident Angle
Degree
Temperature (℃）
Distinguish between the Real Displacement and the Artificial Ones
From Patterns of Distribution
Initial Star position on CCD
Displacement due to thermal
expansion etc.
Displacement due to lunar rotation
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-arcseconds 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-arcseconds.
 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-arcseconds 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.