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Smith C.,EOS Space Systems Pty Ltd
Advances in the Astronautical Sciences

The relatively high levels of uncertainty in orbit predictions available from the current space surveillance and tracking systems has been established as the primary cause of the failure to predict (and avoid) the recent space crash between an active (Iridium) telecommunications satellite and a large debris object (a defunct Cosmos spacecraft). The most effective solution to this problem is by making significantly higher accuracy observations of satellite orbits. Incorporating laser tracking systems into the existing network offers an alternative approach to radars that could potentially provide high-precision orbit updates for critical objects. EOS laser tracking systems use a short pulse laser range finder system and have already demonstrated the basic ability to track small space objects (< 10 cm diameter), and determine their location in space to within a few meters. This paper describes the laser tracking systems and provide some results from the tracking demonstrations and precision orbit determinations. Also described are some upgrades that are currently being undertaken to extend the performance of the system and provide full automation of the tracking station operations. Source

Fowkes N.,University of Western Australia | O'Brien R.,EOS Space Systems Pty Ltd
Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences

We extend the classic Michaelis-Menten kinetics model of the enzyme-mediated conversion of substrate to product to situations in which the enzymes need to diffuse through the underlying structure to reach unconverted substrate and in which the diffusivity is greatly increased by the conversion. The work was prompted by the study of the germination and modification of barley grain that occurs during malting, but is broadly applicable. A nonlinear diffusion, enzyme reaction model of the modification process is proposed and some accurate approximate analytic solutions are derived. We find that a sharp modification front is set up between the modified and the unmodified regions of the barley grain. This front propagates with an almost constant speed through the medium and our findings are consistent with the available experimental observations. © 2009 The Royal Society. Source

Smith C.H.,EOS Space Systems Pty Ltd | Greene B.,Electro Optic Systems Pty.
33rd AIAA International Communications Satellite Systems Conference and Exhibition, ICSSC 2015

Space debris collision avoidance requires accurate space debris orbits, to allow confident manoeuvre of an operational satellite to avoid a predicted collision. Operational spacecraft do not have sufficient on-board fuel to manoeuvre with the frequency, and for the long distances, required by the large uncertainties or errors in space debris positions as currently available. There is a significant demand for larger and more accurate space debris catalogues for this reason. Emerging technologies offer the possibility of moving space debris to avoid a collision, either as an alternative to moving an operational spacecraft, or to prevent debris-debris collisions which would add to the overall space debris burden. However any manoeuvre of space debris requires very high levels of confidence that the new, contrived space debris orbit is less likely to cause harm than the old/current orbit. This requires even higher levels of space tracking capability and capacity than have been projected for conventional collision avoidance purposes. We will discuss emerging space tracking capabilities and the prospects of meeting the space tracking and catalogue requirements for both these classes of activity. © 2015, American Institute of Aeronautics and Astronautics Inc, AIAA. All Rights Reserved. Source

Sang J.,Wuhan University | Bennett J.C.,RMIT University | Bennett J.C.,EOS Space Systems Pty Ltd | Smith C.,EOS Space Systems Pty Ltd
Acta Astronautica

In the last 2 years EOS Space Systems has conducted three debris tracking campaigns using its Space Debris Tracking System (SDTS) at Mt. Stromlo. The first one was an optical (passive) tracking campaign undertaken in May 2012. The second one was a laser tracking campaign in July/August 2012, and the third one was also a laser tracking campaign in April/May 2013. One of the main objectives was to assess the performance of short-term (1-2 days) debris orbit predictions (OPs) using single-station tracking data from Mt. Stromlo. This paper presents comprehensive results and analyses for the assessment of short-term OP accuracy. It shows that 1-day OP accuracy better than 20 arcsec is achievable using only 2 passes of tracking data over 24 h. © 2014 IAA. Source

Bennett J.C.,RMIT University | Bennett J.C.,EOS Space Systems Pty Ltd | Sang J.,Wuhan University | Smith C.,EOS Space Systems Pty Ltd | Zhang K.,RMIT University
Advances in Space Research

The requirement to regularly track an increasing number of objects will result in straining existing tracking networks. This paper investigates the orbit prediction capability of an orbit determination process using very short-arc optical and laser debris tracking data for objects in low-Earth orbits. An analysis is carried out to determine the reduction in orbit prediction accuracy when tracking data over 5 s from each pass is only available for an orbit determination. The results show that the reduction in accuracy is not extensive and good orbit predictions are still possible when using only 5 s of data from the beginning of each pass. The results are achievable due to an accurate ballistic coefficient estimation and accurate tracking data. The dependence of the results on the perigee altitude of the objects is obvious, indicating modelling error of the atmospheric mass density in lower orbits remains the dominant source of error. © 2014 COSPAR. Source

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