Reference Calibration for Precision Dark Energy Measurement

不确定的光度标准现在构成了我们对暗能量知识的主要不确定性。 此外，它们构成了一个重要的系统，用于测量星系团中的恒星数量，以及即将到来的测量结构增长的光度红移巡天。标准星星通量的不确定性有改善的前景，但从大气层上方测量恒星通量的传统技术存在基本和固有的问题：所有恒星源的可变性，以及难以建立一个精确校准、交叉检查和稳定的地球大气层上方观测平台。 我们正在进行一项研究计划，以了解和深刻减少许多天体物理学和宇宙学的不确定性，由于测光。目前，我们与多伦多、麦吉尔、NRC-INMS和美国机构的同事一起，设计并建造了高空气球的有效载荷，其中包含单色光源和辐射校准。我们的热气球飞行已经开始飞越天文台，从2011年8月我们在新罕布什尔州的首次试飞开始，并继续在新墨西哥州校园天文台和Mt. 2012年在亚利桑那州的霍普金斯天文台，次年在智利的CTIO和拉斯坎帕纳斯天文台。 我们已经建造并负责有效载荷光学系统，包括光源、积分球和稳压电源。除了我们最初的自由飞行气球有效载荷外，测试台和系留气象气球上的校准有效载荷分别在光学台和新的32”UVic望远镜天文台上采集数据。与加拿大同事单独提交的RTI赠款一起，我们目前要求资助一名理学硕士学生分析飞越数据，以及我们在UVic的校准光源观测数据。该计划的长期目标是在纳米卫星上校准源，以及在受控的高空微型飞艇上，直接飞到SNIa的“前面”，并允许世界各地的天文台达到当时技术限制的0.01%测光精度。

Uncertainties on photometric standards now constitute the dominant uncertainty on our knowledge of dark energy. Additionally, they constitute a significant systematic for measurements of stellar population in galaxy cluster counts, and upcoming photometric redshift surveys measuring growth of structure. There are prospects for improvement in uncertainties from standard star flux, but the traditional techniques of measurement of stellar flux from above the atmosphere suffer from basic and inherent problems: the variability of all stellar sources, and the difficulty of creating a precisely calibrated, cross-checked, and stable platform for observation above Earth's atmosphere. We are undertaking a program of research to understand and profoundly reduce the many astrophysical and cosmological uncertainties due to photometry. Presently, together with colleagues at Toronto, McGill, NRC-INMS, and U.S. institutions, we have designed and constructed payloads for high-altitude balloons containing both monochromatic light sources and radiometric calibration. Our balloon flights have begun to overfly observatories, starting with our initial test flight in New Hampshire in August 2011, and continuing with a campaign of flights over the Univ. of New Mexico campus observatory and Mt. Hopkins in Arizona in 2012, and the following year with the CTIO and Las Campanas observatories in Chile. We have constructed and are the responsible party for the payload optics, including the light source, integrating sphere, and regulated power supply. As well as our initial free-flying balloon payload, both a teststand, and a calibrated payload on a tethered weather balloon, are taking data on an optical table and with the new 32" UVic telescope observatory, respectively. Together with an RTI grant with Canadian colleagues submitted separately, we presently request funding for an MSc student to analyze the data from the overflights, as well as from our calibrated lightsource observations at UVic. The longer-term goals of the program are calibrated sources on a nanosatellite, as well as on a controlled high-altitude miniature blimp, to fly directly "in front of" SNIa, and allow observatories across the world to reach the then-technology-limited precision of 0.01% photometry.