Enhancing GBT metrology to support high resolution 3mm molecular imaging for the U.S. Community

绿色银行望远镜（GBT）是世界上最大的全可控望远镜，也是美国科学界的独特资产。 它的表面比一个足球场还大，必须非常精确地调整，以使入射的无线电波聚焦，因此表面设计有2000多个安装在精密电机上的独立面板。 电机可以移动面板，以补偿与完美形状的任何偏差。 虽然这在夜间效果很好，但在白天很难进行这种调整，因为阳光照射在盘子的不同部分会导致温度变化和目前无法测量的不可预测的失真。 这些失真限制了GBT在其最高工作频率下的使用，其中表面精度的公差是最严格的。 目前的项目将在GBT上安装一个激光测距测量系统，该系统将非常精确地测量任何表面变形，使GBT能够在白天和黑夜都精确聚焦。 这将使望远镜在其最高工作频率下的可用时间每年增加多达1,000小时，GBT的科学产出及其对美国科学界广泛调查的效用也相应增加。绿色银行观测站还通过其游客中心支持广泛的公共外展活动。 计划对绿色银行望远镜（GBT）计量系统进行改进，以便在白天能够在3毫米波段扩大操作。这项工作将使3毫米望远镜的可用时间增加两倍，并将分子丰富的内银河平面和银河中心的可用时间增加四倍。 商业计量领域的最新技术进步使得购买地面激光扫描仪（TLS）成为可能，当安装在GBT的主焦点附近时，可以在一到两分钟内扫描整个盘，产生约1000万个数据点，单个范围精度为几mm。对这些数据的最小二乘拟合提供了表面的估计，精度约为30微米rms，明显优于当前的“散焦全息”方法，并且远远超过所需的精度。测量表面将与理想表面进行比较，以向表面面板致动器发出命令，从而补偿热畸变。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The Green Bank Telescope (GBT) is the world's largest fully-steerable telescope and a unique asset for the US scientific community. Its surface, which is larger than a football field, must be adjusted very precisely to bring the incoming radio waves into focus, so the surface was designed with more than 2000 individual panels mounted on precise motors. The motors can move the panels to compensate for any deviations from the perfect shape. While this works quite well at night, it can be very difficult to make this adjustment during daylight hours, when sunlight falling on different parts of the dish causes temperature changes and unpredictable distortions that cannot currently be measured. These distortions limit use of the GBT at its highest operating frequencies, where tolerances on surface accuracy are the tightest. The current project will implement a laser ranging measurement system on the GBT that will measure any surface distortions very accurately, allowing the GBT to be focused precisely both day and night. This will increase the available usable time of the telescope at its highest operating frequencies by as much as 1,000 hours every year, with a corresponding increase in the scientific output of the GBT and its utility to the US scientific community for a broad range of investigations. The Green Bank Observatory also supports a wide range of public outreach activities through its visitor center. Enhancements to the Green Bank Telescope (GBT) metrology system are planned that will enable expanded operation in the 3mm wavelength band during daylight hours. This work will increase the usable telescope time at 3mm by as much as a factor of two, and increase available time on the molecule-rich inner Galactic plane and the Galactic center by up to a factor of four. Recent technological advances in commercial metrology make it possible to purchase a Terrestrial Laser Scanner (TLS) which, when mounted near the prime focus of the GBT, can scan the entire dish in one to two minutes, producing ~10 million data points with individual range accuracies of the order of a few mm. A least-squares fit to these data provides an estimate of the surface with accuracies ~30 microns rms, significantly better than the current method of "out-of-focus holography" and well in excess of the accuracy needed. The measured surface would be compared to the ideal surface to produce commands to the surface panel actuators to compensate for the thermal distortions.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.