Warwick representation at AMOS 2019
CSDA members James Blake and Paul Chote presented their research at the 2019 AMOS Conference, with the following proceedings:
- J. A. Blake, P. Chote, D. Pollacco, D. Veras, et al., Optical imaging of faint geosynchronous debris with the Isaac Newton Telescope. In the six decades following the launch of Sputnik 1, thousands of satellites have been placed in orbit around the Earth. It has become increasingly apparent that this number is now dwarfed by a population of artificial debris originating from launch hardware, break-ups and long-term deterioration. Recent anomalies exhibited by the geostationary satellites Intelsat 29e, AMC-9 and Telkom 1 have highlighted the existence of a relatively uncharacterised population of faint debris at geosynchronous (GEO) altitudes, where there are no natural removal mechanisms. Previous attempts to catalogue these objects have employed the use of 1 m class optical telescopes, but regular monitoring is challenging, thus our knowledge remains sparse. We conducted a blind survey of faint geosynchronous debris using eight nights of dark/grey time on the 2.54 m Isaac Newton Telescope in La Palma, Canary Islands. A total of 129 objects with on-sky angular rates consistent with GEO were detected. We probe down to V = 21, corresponding to objects ∼ 10 cm assuming an albedo of 0.1. We compare our sampled population to those of earlier surveys. The faint end of our brightness distribution continues to grow until the sensitivity limit is reached, suggesting that the modal brightness could be even fainter. Perhaps most interestingly, a subset of faint, uncorrelated detections are rapidly tumbling such that they straddle the limiting magnitude of our observations over the course of a single exposure. These pose a rather complex issue due to the difficulty in obtaining an estimate of object size with such variation in brightness. We present a preliminary analysis based on light curves extracted from our sampled population of objects in the GEO regime. This work is part of an ongoing collaboration between the University of Warwick and the Defence Science & Technology Laboratory to investigate the population of faint geosynchronous debris.
- P. Chote, J. A. Blake, and D. Pollacco, Precision Optical Light Curves of LEO and GEO Objects. Optical light curves are becoming an essential tool for classifying and characterising the properties of resident space objects. The intensity and colour of reflected sunlight probes the structure and reflectivity of the object, which evolves on a range of timescales due to changes in the objects attitude and the observer-object-sun geometry. Light curves therefore encode a signature of the object's structure and rotational properties, which can be analysed to constrain properties of the objects or applied en-masse to classify unknown objects via machine learning techniques. A new research group has formed at the University of Warwick with a goal of studying the characteristics and dynamics of man-made objects orbiting the Earth. Here we describe two prototype robotic surveys that we are undertaking to obtain high-cadence, precisely calibrated light curves for objects in both LEO and GEO regimes. LEO light curves are being obtained for relatively bright (Gaia G BP < 10) targets using the SuperWASP telescope, which has been reconfigured with a ∼ 200 deg 2 field of view and GPS-based timing. Targets are observed as streaks in sidereally tracked images that tile ∼ 70 % of the pass across the sky, and a custom reduction pipeline extracts light curves with an effective time cadence 100 ms that are calibrated against the Gaia catalogue. The GEO survey uses a temporarily installed 14" f/2.2 telescope and similar observing techniques to obtain a short (∼30 minute) first-pass classification light curve at a < 1 s effective cadence to characterise the short-period variability of geosynchronous objects. We provide an overview of the survey strategies and analysis and present some example results obtained during the first month of operations.