BeyondPlanck V. Planck LFI 的最小化 ADC 修正
BeyondPlanck V. Minimal ADC Corrections for Planck LFI
AI总结：
本文提出了一种用于 BeyondPlanck 框架的最小化 ADC DNL 修正方法，仅在显著受非线性影响的 LFI 数据流上应用，结果显示其对当前宇宙学参数估计影响较小，但未来仍需改进以避免联合分析中的条纹问题。
摘要：
我们描述了在贝叶斯端到端 BeyondPlanck 分析框架中采用的模数转换器（ADC）微分非线性（DNL）修正程序。该方法与为官方 LFI 数据处理中心（DPC）分析开发的方法几乎相同，并依赖于每个探测器数据流的分箱 rms 噪声分布。然而，我们并非直接从原始 rms 分布构建修正分布，而是首先对每个显著的 ADC 诱导的 rms 下降拟合一个高斯函数，然后从这个平滑模型推导出相应的修正模型。这种方法的主要优点是，只有受 ADC DNL 显著影响的样本才会被修正。新的修正仅应用于有明确非线性检测的数据，且其性能至少与 DPC 修正相当。在总共 88 个 LFI 数据流（44 个探测器的天空和参考负载各一个）中，我们在 25 个案例中应用了新的最小化 ADC 修正，并在 8 个案例中保留了 DPC 修正。所有这些修正均应用于 44 或 70 GHz 通道，而与之前的分析一样，30 GHz ADC 没有显示出显著的非线性证据。通过比较 BeyondPlanck 和 DPC ADC 修正方法，我们估计残余 ADC 不确定性比 44 和 70 GHz 通道的总噪声低约两个数量级，其对当前宇宙学参数估计的影响很小。然而，我们也表明 ADC 修正中的非理想性会在最终频率图中产生尖锐的条纹，这对于未来与 HFI、WMAP 或其他数据集的联合分析可能很重要。因此我们得出结论，尽管现有修正足以用于基于 LFI 的宇宙学参数分析，但 LFI ADC 修正的进一步工作仍然是有必要的。
英文摘要：
We describe the correction procedure for Analog-to-Digital Converter (ADC) differential non-linearities (DNL) adopted in the Bayesian end-to-end BeyondPlanck analysis framework. This method is nearly identical to that developed for the official LFI Data Processing Center (DPC) analysis, and relies on the binned rms noise profile of each detector data stream. However, rather than building the correction profile directly from the raw rms profile, we first fit a Gaussian to each significant ADC-induced rms decrement, and then derive the corresponding correction model from this smooth model. The main advange of this approach is that only samples which are significantly affected by ADC DNLs are corrected. The new corrections are only applied to data for which there is a clear detection of the non-linearities, and for which they perform at least comparably with the DPC corrections. Out of a total of 88 LFI data streams (sky and reference load for each of the 44 detectors) we apply the new minimal ADC corrections in 25 cases, and maintain the DPC corrections in 8 cases. All these correctsion are applited to 44 or 70 GHz channels, while, as in previous analyses, none of the 30 GHz ADCs show significant evidence of non-linearity. By comparing the BeyondPlanck and DPC ADC correction methods, we estimate that the residual ADC uncertainty is about two orders of magnitude below the total noise of both the 44 and 70 GHz channels, and their impact on current cosmological parameter estimation is small. However, we also show that non-idealities in the ADC corrections can generate sharp stripes in the final frequency maps, and these could be important for future joint analyses with HFI, WMAP, or other datasets. We therefore conclude that, although the existing corrections are adequate for LFI-based cosmological parameter analysis, further work on LFI ADC corrections is still warranted.
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