Extreme Digitisation For Ground-Based Cosmic Microwave Background Experiments

TL;DR

This paper investigates extreme digitisation of cosmic microwave background data to reduce data volume, finding that three-bit digitisation minimally increases noise while significantly decreasing data size, aiding mission planning.

Contribution

It introduces and evaluates one, two, and three-bit digitisation schemes for CMB data, demonstrating their effectiveness in reducing data volume with minimal noise increase.

Findings

Three-bit digitisation increases noise by less than 2%.

Data volume is reduced by a factor of ten with three-bit digitisation.

Digitisation noise is a constant percentage of detector noise.

Abstract

The large size of the time ordered data of cosmic microwave background experiments presents challenges for mission planning and data analysis. These issues are particularly significant for Antarctica- and space-based experiments, which depend on satellite links to transmit data. We explore the viability of reducing the time ordered data to few bit numbers to address these challenges. Unlike lossless compression, few bit digitisation introduces additional noise into the data. We present a set of one, two, and three bit digitisation schemes and measure the increase in noise in the cosmic microwave background temperature and polarisation power spectra. The digitisation noise is independent of angular scale and is well-described as a constant percentage of the original detector noise. Three bit digitisation increases the map noise level by < 2%, while reducing the data volume by a factor of ten relative to 32-bit floats. Extreme digitisation is a promising strategy for upcoming experiments.