An External Calibrator for HI Observatories

现代天文学的一个令人兴奋和具有重要科学意义的前沿是推动理解再电离时代(EOR)，这是一个遥远的过去，当时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”，被认为可能充满了新的发现，也是在不久的将来需要理解的关键问题之一。考虑到这一点，正在开发一些创新的仪器，包括新的射电天文阵列，如Murchison Widefield阵列(MWA)和用于探测再电离时代的精密阵列(论文)。从这类仪器中准确地提取所需信息需要不寻常的仪器校准措施，而这一建议解决了这一需要，即通过建立ECHO，一架直升机无人机在望远镜阵列上携带测试发射器，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准确消除与所寻求的EoR发射无关的外部来源造成的前景发射。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%的水平上是不确定的；该项目打算将MWA和纸张的这一限制降低到1%。科学回报可能非常大。ECHO项目将招收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以学生的强烈参与为特色。该项目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.