Direct Comb-Line Measurement: A New Calibration Concept for Astronomical Spectrographs

直接梳线测量：天文摄谱仪的新校准概念

• 批准号: ST/X002845/1
• 负责人: Derryck Reid
• 金额: $ 4.69万
• 依托单位: Heriot-Watt University
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2022
• 资助国家: 英国
• 起止时间: 2022 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=ST%2FX002845%2F1
• 关键词: Direct; Comb; Line; Measurement; New

For decades, astronomers have used hollow-cathode lamps as calibration sources for the spectrographs in optical telescopes, but their limitations mean that the community is now turning to laser frequency combs (LFCs), which provide a sequence of ultra-narrow, drift-free, regularly spaced optical frequencies on a selectable multi-GHz grid.Supported by STFC, HWU is leading the development and deployment of LFCs on several fronts, with current funding from PPRP (ST/S001328/1) and consortium (ST/V000403/1) grants.This capital equipment request directly supports our consortium grant, ST/V000403/1, in which a key goal is to develop LFC-based concepts to extract the wavelength solution of an astronomical spectrograph i.e. its "pixel-to-wavelength" mapping.In ST/V000403/1 we have already developed a comb-line-resolving spectrograph to pilot absolute calibration ideas. Unlike a sealed commercial instrument, we can access the focal plane of this device and place a mask there to use it as a high-resolution spectral shaper, before the light is then directed to an astronomical spectrograph. We propose to achieve this using a high-resolution digital micromirror device (DMD) containing 4 million tiny (7.6 micron) digitally-addressable mirrors.This concept offers some exciting possibilities for conditioning the light sent to the astronomical spectrograph. The most radical of these is to isolate a SINGLE COMB MODE and measure its wavelength to high precision with a commercial wavemeter before injecting it into the astronomical spectrograph. Repeating this process for each order of the spectrograph gives a direct means of obtaining the wavelength solution of each order, unlike current methods which provide just one fiducial wavelength marker for the whole spectrum.Preliminary calculations and an experimental sensitivity check show that this idea should be entirely feasible. The concept removes the uncertainty of which exact comb mode is observed on each order of the spectrograph, a problem normally addressed only by resorting to secondary measurements with a hollow-cathode lamp, or using a complex single-frequency laser locked to the LFC.Further opportunities exist to use the shaper to provide full-spectrum dynamic-range control by selectively attenuating brighter parts of the comb, and to implement switchable comb-mode spacings by selectively removing every nth comb line.Specifically, two items of equipment are requested to construct a prototype spectral shaper (forming a single equipment item): 1. DMD and driver board (Vialux DLP SuperSpeed V-Module) @ £12,202 2. Precision wavemeter (High Finesse WS7-60) @ £26,130Both items have a value below the regulated procurement threshold of £50,000, so no tender process is required. Orders will be placed under a non-competitive action, because of the unique performance capabilities of each item.Lead times for both items are a maximum of 16 weeks, so both can be ordered, delivered and receipted within the lifetime of the capital equipment grant.Including VAT and a 20% contribution from Heriot-Watt University, the final cost to STFC is £36,799, making this a relatively low cost capital equipment request that could offer considerable value to the astronomy community by piloting a new digital calibration approach for astronomical spectrographs.

几十年来，天文学家一直使用空心阴极灯作为光学望远镜中频谱图的校准源，但是它们的局限性意味着社区现在正在转向激光频率梳子（LFC），这些combs（LFCS）无需超鼻涕，无需散布的光学频率，定期开发了iSpect fired of iSppp pectip.sspeppep。 LFC在几个方面的部署以及当前来自PPRP（ST/S001328/1）和财团（ST/V000403/1）的资金。此资本设备请求直接支持我们的财团授予，ST/V000403/1，在这一主要目标中，关键目标是开发基于LFC的概念以开发LFC的概念，以开发出来的范围。在st/v000403/1中，我们已经开发了一个梳量清除的光谱仪以实行绝对校准的想法。与密封的商业仪器不同，我们可以访问该设备的焦平面，并在那里放置面具作为高分辨率光谱塑形器，然后再将光线定向到天文学光谱仪。我们建议使用包含400万个微小（7.6微米）数字化镜的高分辨率数字微龙设备（DMD）来实现这一目标。这个概念为调理发送给天文学光谱仪的光的光提供了一些令人兴奋的可能性。其中最激进的是将单个梳子模式隔离，并在将其注入天文学光谱仪之前，将其波长与商业波电术表的高精度测量。重复每个频谱阶的过程给出了获得每个阶的波长解决方案的直接含义，与当前方法相比，该方法仅为整个频谱提供一个基准波长标记。初步计算和实验敏感性检查表明，这个想法应该完全可行。该概念消除了在光谱仪的每个顺序上观察到的确切梳子模式的不确定性，通常仅通过使用空心灯光灯来解决次级测量，或使用复杂的单频激光锁定在LFC.FC.FC.FURC.FURC.FURC.FURTHER MOMENATION中，以提​​供全面的动态式零件，并使用复杂的单频激光锁定，以提供全面的动态组合，并使用整形型组合式零件，并使用整形式构造组合式零件，并将其固定在整个范围内，并使用整形设备均方式零件，并将其固定式零件兼容式兼容型组合零件，通过选择性地卸下每条梳子线，请要求两项设备来构建原型光谱塑形器（形成单个设备项目）：1。DMD和驾驶员板（Vialux dlp superspeed v-module） @£12,202 2。精确的vavemeter（Precision wavemeter（Precision Wavemeter）（高级Finesse WS7-60） @ 26,103,130b £50,000，因此不需要招标程序。 Orders will be placed under a non-competitive action, because of the unique performance capabilities of each item.Lead times for both items are a maximum of 16 weeks, so both can be ordered, delivered and received within the lifetime of the capital equipment grant.Including VAT and a 20% contribution from Heriot-Watt University, the final cost to STFC is £36,799, making this a relatively low cost capital equipment request that could offer considerationable value to the astronomy community by为天文光谱仪试行一种新的数字校准方法。