Development of a digital zenith telescope for advanced astrometry

Like other optical astrometric techniques, the Photographic Zenith Tube (PZT) has played a key role in the past observations of the Earth rotation, and it also has a potential to be applied to several other observations by taking advantage of automatic observations with self compensation of tilt of the tube. We here propose In-situ Lunar Orientation Measurement (ILOM) to study lunar rotational dynamics by direct observations of the lunar rotation from the lunar surface by using a small telescope like PZT with an accuracy of 1 milli-seconds of arc (1 mas) in the post-SELENE mission. Our second application is to obtain local gravity field on the Earth by combining deflection of the vertical measured by PZT and the position measured by Global Positioning System (GPS) or Global Navigation Satellite System (GNSS). The accuracy required for this purpose is not as strict as ILOM. We have already developed a Bread Board Model (BBM) of the telescope for ILOM and made some experiments in order to know the performance of the driving mechanism under a similar condition to the lunar environment showing high vacuum, large temperature change and dusty condition. We have also shown that it is possible to correct the effects of uniform temperature change upon the optical system by using a simple model with an accuracy of better than 1 mas. This model has the potential to attain the accuracy of 1 mas, based on the results of the experiments and the simulations. © 2012 Science China Press and Springer-Verlag Berlin Heidelberg

Development of a small telescope like PZT and effects of vibrations of mercury surface and ground noise

© 2017, Pleiades Publishing, Ltd. A PZT type telescope for observations of gravity gradient and lunar rotation was developed, and a Bread Board Model (BBM) for ground experiments was completed. Some developments were made for the BBM such as a tripod with attitude control system, a stable mercury pool and a method for collecting the effects of vibrations. Laboratory experiments and field observations were performed from August to September of 2014, in order to check the entire system of the telescope and the software, and the results were compared to the centroid experiments which pursue the best accuracy of determination of the center of star images with a simple optical system. It was also investigated how the vibrations of mercury surface affect the centroid position on Charge Coupled Device (CCD). The results of the experiments showed that the effects of vibrations are almost common to stars in the same view, and they can be corrected by removing mean variation of the stars; and that the vibration of mercury surface can cause errors in centroid as large as 0.2 arcsec; and that there is a strong correlation between the Standard Deviation (SD) of variation of the centroid position and signal to noise ratio (SNR) of star images. It is likely that the accuracy of one (1) milli arcsecond is possible if SNR is high enough and the effects of vibrations are corrected

Development of a digital zenith telescope for advanced astrometry

Like other optical astrometric techniques, the Photographic Zenith Tube (PZT) has played a key role in the past observations of the Earth rotation, and it also has a potential to be applied to several other observations by taking advantage of automatic observations with self compensation of tilt of the tube. We here propose In-situ Lunar Orientation Measurement (ILOM) to study lunar rotational dynamics by direct observations of the lunar rotation from the lunar surface by using a small telescope like PZT with an accuracy of 1 milli-seconds of arc (1 mas) in the post-SELENE mission. Our second application is to obtain local gravity field on the Earth by combining deflection of the vertical measured by PZT and the position measured by Global Positioning System (GPS) or Global Navigation Satellite System (GNSS). The accuracy required for this purpose is not as strict as ILOM. We have already developed a Bread Board Model (BBM) of the telescope for ILOM and made some experiments in order to know the performance of the driving mechanism under a similar condition to the lunar environment showing high vacuum, large temperature change and dusty condition. We have also shown that it is possible to correct the effects of uniform temperature change upon the optical system by using a simple model with an accuracy of better than 1 mas. This model has the potential to attain the accuracy of 1 mas, based on the results of the experiments and the simulations. © 2012 Science China Press and Springer-Verlag Berlin Heidelberg

Development of a small telescope like PZT and effects of vibrations of mercury surface and ground noise

© 2017, Pleiades Publishing, Ltd. A PZT type telescope for observations of gravity gradient and lunar rotation was developed, and a Bread Board Model (BBM) for ground experiments was completed. Some developments were made for the BBM such as a tripod with attitude control system, a stable mercury pool and a method for collecting the effects of vibrations. Laboratory experiments and field observations were performed from August to September of 2014, in order to check the entire system of the telescope and the software, and the results were compared to the centroid experiments which pursue the best accuracy of determination of the center of star images with a simple optical system. It was also investigated how the vibrations of mercury surface affect the centroid position on Charge Coupled Device (CCD). The results of the experiments showed that the effects of vibrations are almost common to stars in the same view, and they can be corrected by removing mean variation of the stars; and that the vibration of mercury surface can cause errors in centroid as large as 0.2 arcsec; and that there is a strong correlation between the Standard Deviation (SD) of variation of the centroid position and signal to noise ratio (SNR) of star images. It is likely that the accuracy of one (1) milli arcsecond is possible if SNR is high enough and the effects of vibrations are corrected