Interference from global navigation satellites in future HI intensity mapping surveys

Abstract

Upcoming HI intensity mapping (IM) surveys will need to achieve unprecedented levels of sensitivity in order to measure the weak integrated emission of extra-galactic HI. Such sensitive surveys will need to overcome many systematic contaminations within the data. One such contaminant originates from the Global Navigation Satellite System (GNSS). Emissions from radio-navigation satellites within the GNSS broadcast across a wide-range of cosmological interesting frequencies (1164 to 1610 MHz), with an in band brightness that is comparable to the Sun. These proceedings use simulations of observations from the upcoming BINGO experiment to explore the effect of GNSS emissions on HI IM data. These simulations are not overly concerned with bright, stochastic events corresponding to a satellite transiting the BINGO main beam response, which can be removed via post-processing of the data. The principle concern is the low-level interactions of the satellites within the side lobes of the BINGO beam and out-of-band transmissions due to the frequency side lobes of the transmitter. The results of these proceedings find that the HI IM signal will be almost three orders-of-magnitude weaker than integrated emission of radio-navigation satellites interacting within the BINGO side lobes. For out-of-band interference, the simulations reveal that the emission from satellites could be comparable to HI signal almost 100 MHz away from the GNSS transmission bands. The implication of these results is that there will be increased challenges for all future HI IM observations of the dark-energy dominated epoch, which includes the proposed BINGO, FAST and SKA1-MID surveys.