On the effect of cosmic rays in bolometric CMB measurements from the stratosphere

TL;DR

This paper investigates how cosmic rays impact the accuracy of bolometric CMB measurements from balloon or satellite missions, revealing that cosmic rays can induce non-gaussian signals and bias power spectrum estimates, especially in highly sensitive experiments.

Contribution

It introduces a simulation-based analysis of cosmic ray effects on bolometric CMB data and evaluates a de-spiking method to mitigate these effects.

Findings

De-spiking effectively removes large cosmic ray events.

Low-level cosmic ray events can mimic non-gaussian features.

Cosmic rays can bias high-multipole power spectrum estimates.

Abstract

Ultra-sensitive bolometric detectors in balloon-borne or satellite missions have the potential to discover low-level non gaussian features in the Cosmic Microwave Background (CMB), due to topological defects or to the inflation process. However, the space environment includes a population of cosmic rays (CR), which produce spurious spikes in bolometric signals. In this paper we analyze how CR affect these measurements and the estimates of non-gaussianity and of angular power spectra of the CMB. Using accurate simulations of noise and CR events in bolometric detectors, we find that a de-spiking technique based on outliers removal in the detector signals contributing to the same sky pixel works well in removing CR events larger than the noise. Low level events hidden in the noise produce skewness and kurtosis of the temperatures of the pixels, indicating low-level non-gaussianity. Moreover, when the low-level CR distribution is not known a-priori, the standard noise estimation pipeline produces a positive bias of the power spectrum at high multipoles. In experiments with detector sensitivity better than 100 $\mu K / \sqrt{Hz}$, in an environment less favorable than the earth stratosphere, the CR-induced non gaussianity is likely to affect significantly the results.