An External Calibrator for HI Observatories

现代天文学的一个令人兴奋和科学上重要的前沿是推动理解再电离时代（EoR），在遥远的过去，第一批恒星开始影响星系之间的物质。 这个时代也被称为“宇宙黎明”，并已被确定为可能充满新的发现和在不久的将来要理解的关键问题之一。 考虑到这一点，一些创新的仪器正在开发中，包括新的射电天文学阵列，如默奇森宽场阵列（MWA）和探测再电离时代的精密阵列（PAPER）。 从这些仪器中精确提取所需信息需要采取不寻常的仪器校准措施，本提案通过建立ECHO解决了这一需求，一架直升机无人机携带测试发射机飞越望远镜阵列，并以非常高的精度调查其实际空间响应模式。从新一代望远镜阵列测量的数据中提取天体物理过程信息的一个关键障碍是精确地去除由于与所寻求的EoR排放无关的外来源而产生的前景排放。 前景发射问题关键取决于对阵列中每个望远镜的建成主光束的准确了解。 目前的技术，如光束建模，在20%的水平是不确定的;本项目打算将MWA和PAPER的限制降低到1%。 ECHO项目将招募和培训对电子学和野外实验感兴趣的本科生，并将在设计、建造和测试的许多阶段中发挥学生的强大参与作用。该项目的资金由NSF天文科学部通过其先进技术和仪器计划提供。

An exciting and scientifically important frontier of modern astronomy is the push to understand the Epoch of Reionization (EoR), a time in the distant past when the first stars began to influence the material between galaxies. This era is also referred to as "Cosmic Dawn", and has been identified as potentially rife with new discoveries and one of the key problems to be understood in the near future. With that in mind, some innovative instrumentation has been under development, including new radio-astronomy arrays suchs as the Murchison Widefield Array (MWA) and the Precision Array for Probing the Epoch of Reionization (PAPER). The precise extraction of the needed information from such instruments requires unusual measures for instrument calibration, and this proposal addresses that need by building ECHO, a helicopter drone to carry a test transmitter over the telescope array and investigate its actual spatial response pattern to a very high precision.A key obstacle to extracting the information on astrophysical processes from data measured by the new generation of telescope arrays is the accurate removal of foreground emission due to extraneous sources unrelated to the EoR emission being sought. That foreground emission problem depends critically on an accurate knowledge of the as-built primary beam of each telescope in the array. Current techniques, such as beam modeling, are uncertain at the 20% level; this project intends to push that limit down to 1% for MWA and PAPER. The scientific payoff is potentially very large.The ECHO project will recruit and train undergraduates interested in electronics and field experiments, and will feature strong student involvement in many phases of design, construction, and testing.Funding for this project is being provided by NSF's Division of Astronomical Sciences through its Advanced Technologies and Instrumentation program.