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arXiv 1007.1765astro-ph.IM
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VLTI的GRAVITY干涉仪的条纹检测Laser计量

The Fringe Detection Laser Metrology for the GRAVITY Interferometer at the VLTI

H. Bartko, S. Gillessen, S. Rabien, M. Thiel, A. Gräter, M. Haug, S. Kellner, F. Eisenhauer, S. Lacour, C. Straubmeier, J. -P. Berger, L. Jocou, W. Chibani, S. … 展开作者

H. Bartko, S. Gillessen, S. Rabien, M. Thiel, A. Gräter, M. Haug, S. Kellner, F. Eisenhauer, S. Lacour, C. Straubmeier, J. -P. Berger, L. Jocou, W. Chibani, S. Lüst, D. Moch, O. Pfuhl, W. Fabian, C. Araujo-Hauck, K. Perraut, W. Brandner, G. Perrin, A. Amorim

摘要:

对大基线上恒星光程长度差的干涉测量可以提供极其精确的天体测量数据。干涉仪GRAVITY将同时测量欧洲南方天文台(ESO)甚大望远镜干涉仪(VLTI)视场中的两个物体,并在仅5分钟内确定其角距,精度为10微弧秒。为了以如此高的精度进行天体测量,通过VLTI和仪器的差分路径长度必须通过激光计量测量(并跟踪,因为地球的旋转将永久地改变它)到甚至更高的精度水平(对应于3分钟内的1 nm)。通常,外差差分路径技术用于纳米精度测量,但这些方法很难跟踪整个光束尺寸,并遵循光路到望远镜的主镜。在这里,我们提出了一个差分路径计量系统的初步设计,开发的重力项目。它测量整个瞳孔尺寸上的仪器差分路径,直到入射瞳孔位置。通过检测望远镜副镜上以及主镜反射后的激光条纹图案来测量微分相位。基于我们提出的设计,我们评估的相位测量精度的基础上可能的统计和系统误差的充分预算。我们表明,这种计量设计满足重力的高精度要求。

英文摘要:

Interferometric measurements of optical path length differences of stars over large baselines can deliver extremely accurate astrometric data. The interferometer GRAVITY will simultaneously measure two objects in the field of view of the Very Large Telescope Interferometer (VLTI) of the European Southern Observatory (ESO) and determine their angular separation to a precision of 10 micro arcseconds in only 5 minutes. To perform the astrometric measurement with such a high accuracy, the differential path length through the VLTI and the instrument has to be measured (and tracked since Earth's rotation will permanently change it) by a laser metrology to an even higher level of accuracy (corresponding to 1 nm in 3 minutes). Usually, heterodyne differential path techniques are used for nanometer precision measurements, but with these methods it is difficult to track the full beam size and to follow the light path up to the primary mirror of the telescope. Here, we present the preliminary design of a differential path metrology system, developed within the GRAVITY project. It measures the instrumental differential path over the full pupil size and up to the entrance pupil location. The differential phase is measured by detecting the laser fringe pattern both on the telescopes' secondary mirrors as well as after reflection at the primary mirror. Based on our proposed design we evaluate the phase measurement accuracy based on a full budget of possible statistical and systematic errors. We show that this metrology design fulfills the high precision requirement of GRAVITY.

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