Kavli Affiliate: Xiang Zhang
| First 5 Authors: Steve Prabu, Paul J Hancock, Xiang Zhang, Steven J Tingay, Torrance Hodgson
| Summary:
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 hours 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 de-coherence 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.
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