We present the design and characterization of a ground-based absolute polarization angle calibrator accurate to better than 0.1 degrees for use with polarization sensitive cosmic microwave background (CMB) experiments. The calibrator's accuracy requirement is driven by the need to reduce upper limits on cosmic polarization rotation, which is expected to be zero in a large class of cosmological models. Cosmic polarization effects such as cosmic birefringence and primordial magnetic fields can generate spurious B-modes that result in non-zero CMB TB and EB correlations that are degenerate with a misalignment of detector orientation. Common polarized astrophysical sources used for absolute polarization angle calibration have not been characterized to better than 0.5 degrees. Higher accuracy can be achieved through self-calibration methods, however these are subject to astrophysical foreground contamination and inherently assume the absence of effects like cosmic polarization rotation. The deficiencies in these two calibration methods highlight the need for a well characterized polarized source. The calibrator we present utilizes a 76 GHz Gunn oscillator coupled to a frequency doubler, pyramidal horn antenna, and co-rotating wire-grid polarizer. We use an accurate bubble level in combination with four precision-grade aluminum planes located within the enclosure to calibrate the source's linear polarization plane with respect to the local gravity vector to better than the 0.1 degree goal. In 2017 the calibrator was deployed for an engineering test run on the POLARBEAR CMB experiment located in Chile's Atacama Desert and is being upgraded for calibration of the POLARBEAR-2b receiver in 2018. In the following work we present a detailed overview of the calibrator design, systematic control, characterization, deployment, and plans for future CMB experiment absolute polarization calibration.
Cosmic Microwave Background experiments need to measure polarization properties of the incoming radiation very accurately to achieve their scientific goals. As a result of that, it is necessary to properly characterize these instruments. However, there are not natural sources that can be used for this purpose. For this reason, we developed the PROTOtype CALibrator for Cosmology, PROTOCALC, which is a calibrator source designed for the 90GHz band of these telescopes. This source is purely polarized and the direction of the polarization vector is known with an accuracy better than 0.1deg. This s…
We describe Cal X-1, a SmallSat mission concept to establish X-ray standard candles in the sky, which will enable absolute calibration of the current and future X-ray observatories. It consists of two CubeSats flying in formation, one containing an absolutely calibrated X-ray source and another, 1-2 km away, a simple X-ray telescope.
The absolute accuracy of the estimated parameters of gravitational wave sources will be fundamentally limited by the calibration uncertainties of the detectors in upcoming observation runs with the increased number of source statistics. Photon calibrators have so far been the primary tools for absolute calibration of test-mass displacement, relying on measurement of the photon pressure. The current technological limit of the absolute calibration uncertainty for gravitational-wave amplitudes is limited to a few percent, due to the uncertainty in the laser power-standard maintained by the metrol…
We analyze the effect of polarized diffuse emission in the calibration of wide-beam mm-wave polarimeters, when using the Crab Nebula as a reference source for both polarized brightness and polarization angle. We show that, for CMB polarization experiments aiming at detecting B-mode in a scenario with a tensor to scalar ratio $r \sim 0.001$, wide (a few degrees in diameter), precise ($σ_Q$ , $σ_U$ $\sim$ 20 $μ$$K_{CMB}$ arcmin), high angular resolution ($< \mathrm{FWHM}$) reference maps are needed to properly take into account the effects of diffuse polarized emission and avoid significant bias…
It is critical for James Webb Space Telescope (JWST) science that instrumental units are converted to physical units. We detail the design of the JWST absolute flux calibration program that has the core goal of ensuring a robust flux calibration internal to and between all the science instruments for both point and extended source science. This program will observe a sample of calibration stars that have been extensively vetted based mainly on Hubble Space Telescope, Spitzer Space Telescope, and Transiting Exoplanet Survey Satellite observations. The program uses multiple stars of three differ…
We describe the Fourier Transform Spectrometer (FTS) used for in-field testing of the POLARBEAR receiver, an experiment located in the Atacama Desert of Chile which measures the cosmic microwave background (CMB) polarization. The POLARBEAR-FTS (PB-FTS) is a Martin-Puplett interferometer designed to couple to the Huan Tran Telescope (HTT) on which the POLARBEAR receiver is installed. The PB-FTS measured the spectral response of the POLARBEAR receiver with signal-to-noise ratio (SNR) $>20$ for $\sim$69% of the focal plane detectors due to three features: a high throughput of 15.1 steradian cm$^{…
Status of the COSmological Microwave Observations CALibrator
Institut d’Astrophysique Spatiale, CNRS-Université Paris-Saclay（空间天体物理研究所）；Institut de Recherche en Astrophysique et Planétologie, CNRS-INSU（天文与行星学研究所在）；Institut de Radio-Astronomie Millimétrique（毫米波射电天文学研究所）；Department of Physics, University of Milano-Bicocca（米兰比可卡大学物理系）；Laboratoire de Physique de l’École normale supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université Paris Cité（巴黎高等师范学院物理实验室）；Laboratoire de Physique Subatomique et de Cosmologie, CNRS（亚原子物理学与宇宙学实验室）；INAF - Osservatorio di astrofisica e scienza dello spazio Bologna（意大利国家天体物理研究所博洛尼亚天文与空间科学观测站）；Institut d’Electronique et des Technologies du numérique（电子与数字技术研究所）；Centre spatial universitaire de Grenoble, Université Grenoble Alpes（格勒诺布尔大学航天中心）；University（大学）
Precision Tests of Parity Violation Over Cosmological Distances
最近通过BICEP 2和POLARBEAR实验对宇宙微波背景$B$模式偏振功率谱的测量已经展示了用于探测基础物理的新的精确工具。不管起源如何，我们能够检测到亚$μ$ K CMB偏振的事实代表了巨大的技术突破。然而，更多的信息可能隐藏在CMB的极化模式中。由于它的张量性质，CMB偏振也可以通过检测宇宙偏振旋转来揭示宇称违反物理学。虽然目前的CMB偏振仪是足够灵敏的测量一个度级偏振旋转与$>5σ$统计意义，他们缺乏区分这种效果从一个系统的仪器偏振旋转的能力。在这里，我们激励从目前的CMB数据以及独立的射电星系和类星体的偏振测量宇宙偏振旋转的搜索。我们认为，校准精度的提高将允许精确测量的奇偶性和洛伦兹违反效果。我们描述了CalSat天基偏振校准器，该校准器将为$0.05^\circ$提供系统偏振角校准不确定性的严格控制--比当前CMB偏振校准器有一个数量级的改进。基于CalSat-based校准可以与当前的CMB偏振仪一起使用，以搜索$B$模式偏振，有效地将它们变成宇宙宇称违反的探测器，即不需要建立专用仪器。
Sensitive radio instruments are optimized for observing faint astronomical sources, and usually need to attenuate the received signal when observing the Sun. There are only a handful of flux density calibrators which can comfortably be observed with the same attenuation setup as the Sun. Additionally, for wide field-of-view (FoV) instruments like the Murchison Widefield Array (MWA) calibrator observations are generally done when the Sun is below the horizon to avoid the contamination from solar emissions. These considerations imply that the usual radio interferometric approach to flux density …
STARSFLUX: an all-sky catalogue of absolute spectro-photometric calibrators from 0.3 to 30 $μ$m
STAR Institute, Institut d’Astrophysique et de Géophysique, University of Liège（列日大学天体物理与地球物理研究所）；Sterrewacht Leiden, Leiden University（莱顿大学莱登天文台）；Anton Pannekoek Institute for Astronomy, University of Amsterdam（阿姆斯特丹大学安东·潘内库克天文学研究所）；Max-Planck-Institut für Astronomie（马克斯·普朗克天文学研究所）；Konkoly Observatory, HUN-REN Research Centre for Astronomy and Earth Sciences（孔科利天文台，匈牙利研究与教育网络地球科学与天文学研究中心）；Laboratoire Lagrange, Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS（蔚蓝海岸大学拉格朗日实验室，蔚蓝海岸天文台，法国国家科学研究中心）；Hamburger Sternwarte（汉堡天文台）；Department of Physics & Astronomy, University of Southampton（南安普顿大学物理与天文学系）
The paper presents the results of the largest to date VLBI absolute astrometry campaign of observations of 13,645 radio sources with the Very Long Baseline Array (VLBA). Of them, 7220 have been detected, including 6755 target sources that have never been observed with VLBI before. This makes the present VLBI catalogue the largest ever published. Positions of the target sources have been determined with the median uncertainty 1.7 mas, and 15,599 images of 7179 sources have been generated. Unlike to previous absolute radio astrometry campaigns, observations were made at 4.3 and 7.6 GHz simultane…
The precise calibration of the strain readout of the LIGO gravitational wave observatories is paramount to the accurate interpretation of gravitational wave events. This calibration is traditionally done by imparting a known force on the test masses of the observatory via radiation pressure. Here we describe the implementation of an alternative calibration scheme: the Newtonian Calibrator. This system uses a rotor consisting of both quadrupole and hexapole mass distributions to apply a time-varying gravitational force on one of the observatory's test masses. The force produced by this rotor ca…
The Nancy Grace Roman Space Telescope's (Roman) Coronagraph Instrument is a technology demonstration equipped to achieve flux contrast levels of up to 10$^{-9}$. This precision depends upon the quality of observations and their resultant on-sky corrections via an absolute flux calibration (AFC). Our plan utilizes 10 dim and 4 bright standard photometric calibrator stars from Hubble Space Telescope's (HST) CALSPEC catalog to yield a final AFC error of 1.94\% and total observation time of $\sim$22 minutes. Percent error accounts for systematic uncertainties (filters, upstream optics, quantum eff…
As the sensitivities of LIGO, Virgo and KAGRA detectors improve, calibration of the interferometers output is becoming more and more important and may impact scientific results. For the observing run O3, Virgo used for the first time photon calibrators (PCal) to calibrate the interferometer, using radiation pressure of a modulated auxiliary laser beam impinging on the Advanced Virgo end mirrors. Those optical devices, also used in LIGO, are now the calibration reference for the global gravitational wave detectors network. The intercalibration of LIGO and Virgo PCals, based on the same absolute…
A tremendous international effort is currently dedicated to observing the so-called primordial B modes of the Cosmic Microwave Background (CMB) polarisation. If measured, this faint signal imprinted by the primordial gravitational wave background, would be an evidence of the inflation epoch and quantify its energy scale, providing a rigorous test of fundamental physics far beyond the reach of accelerators. At the unprecedented sensitivity level that the new generation of CMB experiments aims to reach, every uncontrolled instrumental systematic effect will potentially result in an analysis bias…
The quest for primordial gravitational waves enclosed in the Cosmic Microwave Background (CMB) polarization B-modes signal motivates the development of a new generation of high sensitive experiments (e.g. CMB-S4, LiteBIRD) that would allow them to detect its imprint.Neverthless, this will be only possible by ensuring a high control of the instrumental systematic effects and an accurate absolute calibration of the polarization angle. The Crab nebula is known to be a polarization calibrator on the sky for CMB experiments, already used for the Planck satellite it exhibits a high polarized signal …
Status and future development of the COSMOCal Project for absolute CMB polarization calibration
Université Grenoble Alpes, CNRS, LPSC Grenoble（格勒诺布尔阿尔卑斯大学）；International School for Advanced Studies (SISSA)（高等高级研究学院）；INFN Sezione di Trieste（的里雅斯特INFN分部）；Institut de Recherche en Astrophysique et Planétologie（天体物理学和行星学研究所）；Institut de Radio-Astronomie Millimétrique（毫米波射电天文学研究所）；Department of Physics, University of Milano-Bicocca（米兰比可卡大学物理系）；Laboratoire de Physique de l’Ecole normale supérieure（巴黎高等师范学院物理实验室）；INAF - Osservatorio di astrofisica e scienza dello spazio Bologna（博洛尼亚天文物理与空间科学观测站）；Univ. Grenoble Alpes, CNRS, IPAG（格勒诺布尔阿尔卑斯大学）；Institut d’Electronique et des Technologies du numérique（电子与数字技术研究所）；Laboratoire de Physique des 2 infinis Irène Joliot-Curie（伊雷娜·约里奥-居里双无穷物理实验室）；Institut d’Astrophysique Spatiale（天体物理学研究所）；Centre Spatial Universitaire de Grenoble（格勒诺布尔大学航天中心）；Dipartimento di Fisica, Università di Roma “Tor Vergata”（罗马“托尔维加塔”大学物理系）；INAF - Osservatorio Astronomico di Cagliari（卡利亚里天文观测站）；Sapienza Università di Roma（罗马智慧大学）；Department of Physics, Boston University（波士顿大学物理系）；LERMA, Observatoire di Paris-PSL（巴黎天文台）
The Primordial Inflation Explorer (PIXIE) is an Explorer-class mission concept to measure cosmological signals from both linear polarization of the cosmic microwave background and spectral distortions from a perfect blackbody. The targeted measurement sensitivity is 2--4 orders of magnitude below competing astrophysical foregrounds, placing stringent requirements on instrument calibration. An on-board blackbody calibrator presents a polarizing Fourier transform spectrometer with a known signal to enable conversion of the sampled interference fringe patterns from telemetry units to physical uni…
A challenge in absolute calibration is to relate very bright stars with physical flux measurements to faint ones within range of modern instruments, e.g. those on large groundbased telescopes or on the James Webb Space Telescope (JWST). We propose Sirius as the fiducial color standard: it is an A0V star that is slowly rotating and does not have infrared excesses either due to hot dust or a planetary debris disk; it also has a number of accurate (~ 1 - 2%) absolute flux measurements. We transfer the near infrared flux from Sirius accurately to BD +60 1753, an unobscured early A-type star (A1V, …
Calibration of the Herschel SPIRE Fourier Transform Spectrometer
Herschel SPIRE仪器由成像光度照相机和成像傅里叶变换光谱仪（FTS）组成，两者都在450-1550 GHz的频率范围内工作。在本文中，我们简要地回顾了FTS的设计，操作和数据处理，并详细描述了相对校准（去除仪器签名）和绝对校准对标准天文源的方法。校准方案假设一个空间扩展的源，并使用赫歇尔望远镜作为主要的校准器。从扩展到点源校准的转换是使用天王星的观测进行的。望远镜发射的模型被证明是精确到6%以内，可重复性好于0.06%，与火星和海王星的模型相比，天王星模型被证明是精确到3%以内。对多个点源的多次观测表明，在校正卫星绝对指向误差（APE）的影响后，定标的重复性优于1%。卫星APE导致导出的通量减少，在任务的第一部分中，在SPIRE范围的高频端，其可以高达~10%（1 sigma），并且在Herschel操作第1011天之后为~4%。由于较大的波束尺寸，SPIRE频带的较低频率范围不受此指向误差的影响。总体而言，对于指向良好的点状源，绝对通量校准优于6%，对于需要映射的扩展源，绝对通量校准优于7%。
The hierarchy of motions that we are participating is well known, from the Earth's motion around the Sun and Sun's motion in the Milky Way, up to the Local Group's motion within the Virgo Supercluster of galaxies. The dipole anisotropy of the Cosmic Microwave Background (CMB) enables to define Sun's motion with respect to the CMB "absolute" frame. We now present evidence for CMB Galactic dipole signal due to the Sun's motion in the Galaxy, by means of Planck 2018 data and Gaia Early Data Release 3. The signal is weak and frequency depended, the strongest is at 30 GHz, up to 7.6σconfidence. The…
CMBolic: Symbolic emulators for the Cosmic Microwave Background. I. Lensing
CEICO, Institute of Physics of the Czech Academy of Sciences（捷克科学院物理研究所）；Institute of Theoretical Physics, Faculty of Mathematics and Physics, Charles University（查理大学数学物理学院理论物理研究所）；Astrophysics, University of Oxford（牛津大学天体物理学系）；Institute of Cosmology & Gravitation, University of Portsmouth（朴茨茅斯大学宇宙学与引力研究所）
The BICEP3 CMB Polarimeter is a small-aperture refracting telescope located at the South Pole and is specifically designed to search for the possible signature of inflationary gravitational waves in the Cosmic Microwave Background (CMB). The experiment measures polarization on the sky by differencing the signal of co-located, orthogonally polarized antennas coupled to Transition Edge Sensor (TES) detectors. We present precise measurements of the absolute polarization response angles and polarization efficiencies for nearly all of BICEP3s $\sim800$ functioning polarization-sensitive detector pa…
