Denis Vida, University of Western Ontario; Michael Mazur, University of Western Ontario; Peter G. Brown, University of Western Ontario; Stanimir Metchev, University of Western Ontario; David L. Clark, University of Western Ontario; Tammy Do, University of Western Ontario; Jack Zhang, University of Western Ontario; Lauchie Scott, Defence R&D Canada
Keywords: high cadence, meteor, camera, megaconstellations, open data, Canada, wide field, video
Abstract:
The recent proliferation of megaconstellations in low-Earth orbit (LEO) has led to a need for increased revisit frequency for purposes of space situational awareness (SSA) and environmental impacts. For example, the ability to remove mega-constellation satellite trails from astronomical imagery requires frequent TLE updates, especially for objects with automatic electric propulsion and orbital control. Additionally, with large numbers of operational LEO objects, there is a greater requirement for assessment of spacecraft state of health and stability, which can be addressed, in part, through lightcurve measurements. To meet these goals, we have repurposed software and video cameras designed for faint meteor measurements as part of the Global Meteor Network while still allowing for meteor data collection. Our prototype system consists of a dozen medium to narrow-field video cameras which cover the entire sky above 20 degrees elevation from a single site in a fly’s eye configuration. Each camera has a field of view which covers roughly 100 sq deg of the sky. The system’s limiting sensitivity for LEO objects is to optical magnitudes between +10 and +11, imaging the entire visible sky at 25 Hz. Even higher sensitivity to space objects can optionally be achieved by reducing cadence and increasing the exposure. The wide fields of view are well matched to the Canadian climate where partly cloudy conditions can frequently occur and the software allows for uncued tracking to continue in open clear spots in the sky. The concept of operations is of an all-sky viewing bubble in staring mode where all LEO objects larger than 30 cm crossing the bubble are captured. Initial observations from one prototype system yield in excess of 1000 satellite detections per night with ~1 million individual metric measurements per one 12-hour night. Satellites are tracked in a wide arc across the sky during their whole period of visibility. The narrow-field cameras have a plate scale of ~15 arcseconds per pixel, allowing for a total measurement accuracy of < 5 arcseconds after centroiding and even less after applying a track-and-stack algorithm. Applying custom timing synchronization we have demonstrated millisecond-level timing accuracy. The satellite detection algorithm is a modified meteor-tracking algorithm which relies on detecting linear features in the imagery and registering objects which are consistent with roughly linear motion over time. A machine-learning algorithm is applied to the initial set of detections to achieve a detection accuracy of over 99.9%. The high astrometric accuracy is achieved by applying a novel astrometric method capable of accurately modelling distortions of wide-field lenses. The astrometric calibration is refined for each measurement, ensuring optimal measurement accuracy. Compared to other ground-based camera systems, the high cadence of our system enables accurate tracking of satellite light curves and the determination of their rotation states to an accuracy of ± 0.1 magnitude. Finally, our system is extremely low-cost, enabling wide distribution and little maintenance overhead due to simple design with no moving parts. In addition, the cameras can be adjusted to work in bright environments and during dusk and dawn, enabling tracking of re-entering objects. In this paper, we describe the methodology and first results from this system including calibration accuracy and photometric results of space objects overflying Canada. We describe how this class of sensors can be applied to detecting bright megaconstellation objects and describe the measured photometric appearance of constellation objects above Canada. As of mid-2024, the project is expanding to five sites across Canada, including one in the Arctic Circle. A public-facing webpage is soon to be available which will provide summaries of the detected positions and brightness for LEO objects in near real-time, data exploration, and allow the download of raw measurement data.
Date of Conference: September 17-20, 2024
Track: SDA Systems & Instrumentation