Construction and status of the CHARIS high contrast imaging spectrograph
Construction and status of the CHARIS high contrast imaging spectrograph
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CHARIS高对比度成像光谱仪的构造及现状
DOI：
10.1117/12.2055769
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发表时间：
2014
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通讯作者：
M
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作者：
Tyler Groff;N. J. Kasdin;Mary A. Limbach;Michael Galvin;Michael A. Carr;Gillian Knapp;Timothy Brandt;Craig Loomis;Norm Jarosik;Kyle Mede;Michael W. McElwain;Markus Janson;Olivier Guyon;Nemanja Jovanovic;Naruhisa Takato; Frantz Martinache;M
普林斯顿大学正在建造日冕高角分辨率成像光谱仪（CHARIS），这是斯巴鲁望远镜的积分场光谱仪（IFS）。CHARIS由日本国家天文台资助，旨在拍摄日冕极端自适应光学（SCExAO）和AO 188自适应光学系统提供的日冕图像中的棕矮星和热木星行星的高对比度光谱。该项目目前在普林斯顿大学处于构建和测试阶段。一旦实验室测试完成，CHARIS将在2016年冬季与SCExAO和AO 188集成。CHARIS在J、H和K波段具有高分辨率表征模式。J、H和K波段的平均光谱分辨率分别为R82、R68和R82，其均匀性是新的高折射率材料L-BBH 2的直接结果。CHARIS还具有第二个低分辨率成像模式，跨越J，H和K波段，平均光谱分辨率为R19，这是该仪器独有的功能。两种成像模式下的视场均为2.07x2.07弧秒。SCExAO+CHARIS将探测比其母星星暗五个数量级的物体，内部工作角为80毫弧秒。系外行星成像的主要挑战是日冕图像中准静态斑点的存在。SCExAO有一个波前控制系统来抑制这些散斑，CHARIS将通过硬件设计来解决它们对光谱串扰的影响，这将推动其光学和机械设计。CHARIS将串扰限制在1%以下，对于比相邻光谱亮一个完整数量级的相邻光源。由于CHARIS是在Nasmyth平台上，所以小透镜阵列和棱镜之间的光学对准是高度稳定的。这提高了光谱的稳定性及其在检测器上的取向，并导致数据管道的波长解决方案的更大稳定性。这意味着后处理的不确定性更小，数据管道所需的天空校准程序的开销更小。在这里，我们介绍了科学的情况下，设计，和建设的现状。CHARIS的设计和经验教训突出了在日冕图像中设计高信噪比光谱的IFS时必须考虑的选择。设计方面的考虑和吸取的经验教训可直接应用于今后能够探测可居住区岩石行星的超大型望远镜和空间观测台的系外行星仪器。
Princeton University is building the Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS), an integral field spectrograph (IFS) for the Subaru telescope. CHARIS is funded by the National Astronomical Observatory of Japan and is designed to take high contrast spectra of brown dwarfs and hot Jovian planets in the coronagraphic image provided by the Coronagraphic Extreme Adaptive Optics (SCExAO) and the AO188 adaptive optics systems. The project is now in the build and test phase at Princeton University. Once laboratory testing has been completed CHARIS will be integrated with SCExAO and AO188 in the winter of 2016. CHARIS has a high-resolution characterization mode in J, H, and K bands. The average spectral resolution in J, H, and K bands are R82, R68, and R82 respectively, the uniformity of which is a direct result of a new high index material, L-BBH2. CHARIS also has a second low-resolution imaging mode that spans J,H, and K bands with an average spectral resolution of R19, a feature unique to this instrument. The field of view in both imaging modes is 2.07x2.07 arcseconds. SCExAO+CHARIS will detect objects five orders of magnitude dimmer than their parent star down to an 80 milliarcsecond inner working angle. The primary challenge with exoplanet imaging is the presence of quasi-static speckles in the coronagraphic image. SCExAO has a wavefront control system to suppress these speckles and CHARIS will address their impact on spectral crosstalk through hardware design, which drives its optical and mechanical design. CHARIS constrains crosstalk to be below 1% for an adjacent source that is a full order of magnitude brighter than the neighboring spectra. Since CHARIS is on the Nasmyth platform, the optical alignment between the lenslet array and prism is highly stable. This improves the stability of the spectra and their orientation on the detector and results in greater stability in the wavelength solution for the data pipeline. This means less uncertainty in the post-processing and less overhead for on-sky calibration procedures required by the data pipeline. Here we present the science case, design, and construction status of CHARIS. The design and lessons learned from testing CHARIS highlights the choices that must be considered to design an IFS for high signal-to-noise spectra in a coronagraphic image. The design considerations and lessons learned are directly applicable to future exoplanet instrumentation for extremely large telescopes and space observatories capable of detecting rocky planets in the habitable zone.