Title: Optical Design of PICO, a Concept for a Space Mission to Probe Inflation and Cosmic Origins Show Chinese title

Title: PICO的光学设计，一项探测暴胀和宇宙起源的空间任务概念

Abstract: The Probe of Inflation and Cosmic Origins (PICO) is a probe-class mission concept currently under study by NASA. PICO will probe the physics of the Big Bang and the energy scale of inflation, constrain the sum of neutrino masses, measure the growth of structures in the universe, and constrain its reionization history by making full sky maps of the cosmic microwave background with sensitivity 80 times higher than the Planck space mission. With bands at 21-799 GHz and arcmin resolution at the highest frequencies, PICO will make polarization maps of Galactic synchrotron and dust emission to observe the role of magnetic fields in Milky Way's evolution and star formation. We discuss PICO's optical system, focal plane, and give current best case noise estimates. The optical design is a two-reflector optimized open-Dragone design with a cold aperture stop. It gives a diffraction limited field of view (DLFOV) with throughput of 910 square cm sr at 21 GHz. The large 82 square degree DLFOV hosts 12,996 transition edge sensor bolometers distributed in 21 frequency bands and maintained at 0.1 K. We use focal plane technologies that are currently implemented on operating CMB instruments including three-color multi-chroic pixels and multiplexed readouts. To our knowledge, this is the first use of an open-Dragone design for mm-wave astrophysical observations, and the only monolithic CMB instrument to have such a broad frequency coverage. With current best case estimate polarization depth of 0.65 microK(CMB}-arcmin over the entire sky, PICO is the most sensitive CMB instrument designed to date. Show Chinese abstract

Abstract: 探测宇宙暴胀和起源的探针（PICO）是NASA目前正在研究的一个探针级任务概念。 PICO将探测大爆炸的物理规律和暴胀的能量尺度，限制中微子质量之和，测量宇宙结构的增长，并通过以比普朗克空间任务高80倍的灵敏度绘制宇宙微波背景的全天图来约束其再电离历史。 在21-799 GHz频段和最高频率下的角分分辨率下，PICO将制作银河系同步辐射和尘埃发射的偏振图，以观察磁场在银河系演化和恒星形成中的作用。 我们讨论了PICO的光学系统和焦平面，并给出了当前最佳情况下的噪声估计。 光学设计是一种优化的开放式德拉戈内（open-Dragone）设计，带有冷光阑。 它在21 GHz时提供了衍射极限视场（DLFOV），通量为910平方厘米球面度。 大的82平方度DLFOV包含分布在21个频率带中的12,996个过渡边缘传感器测热计，并保持在0.1 K。我们使用了目前在运行的宇宙微波背景（CMB）仪器中实现的焦平面技术，包括三色多色像素和复用读出。 据我们所知，这是首次在毫米波天体物理观测中使用开放式德拉戈内设计，也是唯一具有如此宽频率覆盖范围的整体式CMB仪器。 根据当前最佳情况估计，整个天空的偏振深度为0.65微开（CMB）-角分，PICO是迄今为止设计的最敏感的CMB仪器。