Potential Impact of Global Navigation Satellite Services on Total Power HI Intensity Mapping Surveys

TL;DR

This paper assesses how global navigation satellite services (GNSS) signals could interfere with future HI intensity mapping surveys, especially at frequencies above 950 MHz, potentially surpassing the HI signal and impacting cosmological measurements.

Contribution

It provides a realistic estimation of GNSS satellite impact on single-dish HI IM surveys, highlighting frequency-dependent interference issues for the first time.

Findings

GNSS signals exceed HI signal above 950 MHz in SKA-like surveys

Interference is significant across all angular scales at high frequencies

Out-of-band leakage from GNSS satellites poses a challenge for future surveys

Abstract

Future total-power single-dish HI intensity mapping (HI IM) surveys have the potential to provide unprecedented insight into late time ($z < 1$) cosmology that are competitive with Stage IV dark energy surveys. However, redshifts between $0 < z < 0.2$ lie within the transmission bands of global navigation satellite services (GNSS), and even at higher redshifts out-of-band leakage from GNSS satellites may be problematic. We estimate the impact of GNSS satellites on future single-dish HI IM surveys using realistic estimates of both the total power and spectral structure of GNSS signals convolved with a model SKA beam. Using a simulated SKA HI IM survey covering 30000 sq. deg. of sky and 200 dishes, we compare the integrated GNSS emission on the sky with the expected HI signal. It is found that for frequencies $> 950$ MHz the emission from GNSS satellites will exceed the expected HI signal for all angular scales to which the SKA is sensitive when operating in single-dish mode.