Forecasting the occupancy of satellite megaconstellations in SKA observations

TL;DR

This paper forecasts the significant impact of satellite megaconstellations on SKA radio telescope observations, highlighting the need for improved RFI mitigation techniques due to high satellite exposure times.

Contribution

It introduces an analytical model to estimate satellite exposure in SKA observations, emphasizing the potential for substantial RFI contamination and the necessity for mitigation strategies.

Findings

SKA-Low could experience 30% to 100% satellite exposure during observations.

SKA-Mid observations below 1 GHz could see satellites for at least 30% of the time.

Satellite RFI will be an unavoidable challenge requiring new mitigation techniques.

Abstract

The Square Kilometre Array (SKA) is expected to start science operations in 2030 and by that time there could be up to 10$^5$ artificial satellites in Earth's orbit, comprising an increase of an order of magnitude compared to 2024. Most of these new satellites will belong to satellite megaconstellations aimed at providing communication services all over Earth. These satellites create radio frequency interference (RFI) that can impact the observations of modern radio telescopes. In this Letter, we forecast the amount of observing time for which the SKA interferometers will be exposed to satellites, risking RFI contamination. We employed an analytical model and considered two cases of exposure to satellites; (1) satellites that only lie in the main beam and (2) satellites that lie in the main beam or the first sidelobe. We show that for SKA-Low, the exposure is high, with satellites in the beam for 30% of the observation time across half of the frequency range, rising up to 100% below 100 MHz. For SKA-Mid, high frequencies are mostly spared, but observations below 1 GHz could also end up seeing satellites for at least 30% of the time. We conclude that satellites will be unavoidable during SKA observing conditions, risking a strong impact on the RFI environment. This will necessitate a concerted effort to obtain accurate measurements of satellite RFI and to improve our understanding of the impact on various science cases. Finally, new mitigation techniques that are less data-destructive than simple flagging must be introduced.