Improved sensitivity for space domain awareness observations with the murchison widefield array

Our previously reported survey of the Low Earth Orbit (LEO) environment using the Murchison Widefield Array (MWA) detected over 70 unique Resident Space Objects (RSOs) over multiple passes, from 20 h of observations in passive radar mode. In this paper, we extend this work by demonstrating two methods that improve the detection sensitivity of the system. The first method, called shift-stacking, increases the statistical significance of faint RSO signals through the spatially coherent integration of the reflected signal along the RSO's trajectory across the sky. This method was tested on the observations used during our previous blind survey, and we obtained a 75% increase in the total number of detections. The second method re-focuses the MWA to the near-field RSO's position (post-observation), by applying a complex phase correction to each visibility to account for the curved wave-front. The method was tested successfully on an MWA extended array observation of an ISS pass. However, the method is currently limited by signal decoherence on the long-baselines (due to the hardware constraints of the current correlator). We discuss the sensitivity improvement for RSO detections we expect from the MWA Phase 3 correlator upgrade. We conclude the paper by briefly commenting on future dedicated Space Domain Awareness (SDA) systems that will incorporate MWA technologies. (C) 2022 Published by Elsevier B.V. on behalf of COSPAR.

Automated summary

In this paper, two methods, namely shift-stacking and phase correction, are demonstrated to improve the detection sensitivity of the Murchison Widefield Array (MWA) in the Low Earth Orbit (LEO) environment. These methods have been successfully tested in previous observations and an observation of the International Space Station (ISS) pass. The paper also discusses the expected sensitivity improvement from the MWA Phase 3 correlator upgrade and the future integration of MWA technologies into dedicated Space Domain Awareness (SDA) systems.