Near-Infrared Tip-Tilt Sensor for Laser Guide Star Adaptive Optics

通过使用激光导星自适应光学（AO）系统，校正地球大气对天文图像的影响的目标已经取得了相当大的成功，该系统提供了分布在大型望远镜孔径上的湍流的定量测量。然而，激光系统本身无法探测到由大气引起的物体图像中的综移，如果进行这种校正，衍射极限点的包围能量可能会增加40%以上。这种“尖端/倾斜”校正只能通过使用一颗自然导星——望远镜视野中相当明亮的自然恒星——与激光投影系统配合使用来实现。由Peter Wizinowich博士和加州天文学研究协会的合作者为夏威夷莫纳克亚山上的凯克10米望远镜建造的近红外尖端/倾斜传感器将实现这一目标。通过在K（2.2微米波长）大气传输波段工作，计划中的系统将提供高带宽（高达1khz）的尖端/倾斜信息，使用2弧分直径区域内的一到三颗恒星，并在整个视野范围内进行校正。此外，焦点校正可以在比标准方案高得多的时间分辨率下使用。凯克望远镜可以说是世界上最先进、最可靠、最具科学生产力的大型望远镜AO系统。管理机构的科学家和技术人员是世界上最有能力的，山顶是一个杰出的观测点。公众可以通过各种方式获得高达30%的观测时间，因此，通过近红外尖端/倾斜校正系统等机制提高望远镜的成像能力，将使美国所有的天文学受益。这项工作的资金由美国国家科学基金会天文科学部通过其先进技术和仪器项目提供。

The goal of correcting the Earth's atmospheric effects on astronomical images has seen considerable success through the use of laser guide star adaptive optics (AO) systems that provide a quantitative measure of the turbulence distributed over the aperture of a large telescope. However, laser systems by themselves cannot detect the ensemble shift in an object's image that is induced by the atmosphere, and the encircled energy in a diffraction-limited spot could be increased by more than 40% if this correction were made. Such a "tip/tilt" correction is only available through the use of a natural guide star - a rather bright natural star included in the telescope field of view - in tandem with the laser projection system. The near-IR tip/tilt sensor being constructed by Dr. Peter Wizinowich and collaborators of the California Association for Research in Astronomy for the Keck 10-m telescope on Mauna Kea, Hawaii will accomplish this goal. By working in the K (2.2 micron wavelength) atmospheric transmission band, the planned system will provide high bandwidth (up to 1 kHz) tip/tilt information using one to three stars in a 2 arcminute diameter area, and enable corrections over that entire field of view. Additionally, focus corrections are available at a much higher time resolution than for standard schemes.The Keck telescopes are arguably the most advanced, reliable, and scientifically productive large-telescope AO systems available anywhere in the world. Scientists and technical staff at the managing institutions are among the most capable in the world, and the mountaintop is an outstanding observing site. Up to 30% of observing time is available to the general community through various means, so improvements in the imaging capabilities of the telescopes through mechanisms like near-IR tip/tilt correction systems benefit all of U.S. astronomy. Funding for this work is being provided by NSF's Division of Astronomical Sciences through its Advanced Technologies and Instrumentation program.