Laser frequency combs (LFCs) are well on their way to becoming the next-generation calibration sources for precision astronomical spectroscopy^1,2,3,4,5,6. This development is considered key in the hunt for low-mass rocky exoplanets around solar-type stars whose discovery with the radial-velocity method requires cm s^–1 Doppler precision⁷. In order to prove such precise calibration with an LFC, it must be compared to another calibrator of at least the same precision. Being the best available spectrograph calibrator, this means comparing it to a second—fully independent—LFC. Here, we report on a test in which two separate LFCs were used to simultaneously calibrate an astronomical spectrograph. Our installation of two LFCs at the ultra-stable two-channel spectrograph HARPS allowed characterization of their relative stability and consistency in calibration at the highest available level. Although the test was limited in time, the results confirm the 1 cm s^–1 stability that has long been anticipated by the astronomical community.

激光频率梳 (LFC) 正在成为精密天文光谱^1,2,3,4,5,6的下一代校准源。这种发展被认为是在追捕围绕太阳能型星，其发现与径向速度的方法的低质量岩石外行星密钥需要厘米小号^-1多普勒精度⁷. 为了证明 LFC 的这种精确校准，必须将其与另一个至少具有相同精度的校准器进行比较。作为最好的光谱仪校准器，这意味着将其与第二个完全独立的 LFC 进行比较。在这里，我们报告了一项测试，其中两个单独的 LFC 用于同时校准天文光谱仪。我们在超稳定的双通道光谱仪 HARPS 上安装了两个 LFC，从而可以在最高可用水平上表征它们的相对稳定性和校准一致性。尽管测试时间有限，但结果证实了天文界长期以来一直期待的 1 cm s ^{–1稳定性。}