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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 | Year: 2014

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.


Bennett J.C.,RMIT University | Bennett J.C.,EOS Space Systems Pty. Ltd. | Sang J.,Wuhan University | Smith C.H.,EOS Space Systems Pty. Ltd. | Zhang K.,RMIT University
Advances in Space Research | Year: 2013

Orbit manoeuvre of low Earth orbiting (LEO) debris using ground-based lasers has been proposed as a cost-effective means to avoid debris collisions. This requires the orbit of the debris object to be determined and predicted accurately so that the laser beam can be locked on the debris without the loss of valuable laser operation time. This paper presents the method and results of a short-term accurate LEO (<900 km in altitude) debris orbit prediction study using sparse laser ranging data collected by the EOS Space Debris Tracking System (SDTS). A main development is the estimation of the ballistic coefficients of the LEO objects from their archived long-term two line elements (TLE). When an object is laser tracked for two passes over about 24 h, orbit prediction (OP) accuracy of 10-20 arc seconds for the next 24-48 h can be achieved - the accuracy required for laser debris manoeuvre. The improvements in debris OP accuracy are significant in other applications such as debris conjunction analyses and the realisation of daytime debris laser tracking. © 2013 COSPAR. Published by Elsevier Ltd. All rights reserved.


Sang J.,Wuhan University | Bennett J.C.,RMIT University | Bennett J.C.,EOS Space Systems Pty. Ltd.
Advances in Space Research | Year: 2014

Earlier studies have shown that an orbit prediction accuracy of 20 arc sec ground station pointing error for 1-2 day predictions was achievable for low Earth orbit (LEO) debris using two passes of debris laser ranging (DLR) data from a single station, separated by about 24 h. The accuracy was determined by comparing the predicted orbits with subsequent tracking data from the same station. This accuracy statement might be over-optimistic for other parts of orbit far away from the station. This paper presents the achievable orbit prediction accuracy using satellite laser ranging (SLR) data of Starlette and Larets under a similar data scenario as that of DLR. The SLR data is corrupted with random errors of 1 m standard deviation so that its accuracy is similar to that of DLR data. The accurate ILRS Consolidated Prediction Format orbits are used as reference to compute the orbit prediction errors. The study demonstrates that accuracy of 20 arc sec for 1-2 day predictions is achievable. © 2014 COSPAR. Published by Elsevier Ltd. All rights reserved.


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


Sang J.,EOS Space Systems Pty Ltd | Bennett J.C.,RMIT University | Smith C.H.,EOS Space Systems Pty Ltd
Advances in Space Research | Year: 2013

This paper presents a new method for estimating ballistic coefficients (BCs) of low perigee debris objects from their historical two line elements (TLEs). The method uses the drag perturbation equation of the semi-major axis of the orbit. For an object with perigee altitude below 700 km, the variation in the mean semi-major axis derived from the TLE is mainly caused by the atmospheric drag effect, and therefore is used as the source in the estimation of the ballistic coefficient. The method is tested using the GRACE satellites, and a number of debris objects with external ballistic coefficient values, and agreements of about 10% are achieved. The method is also applied to estimate the BC values of three low perigee debris objects, which were tracked optically in May 2012 by the EOS Space Debris Tracking System. The single-station sparse tracking data of the three debris objects is processed using the orbit analysis software developed at EOS Space Systems. When tracking data of only 2 passes over about 24 h is available, the errors of orbit predictions for 24 h are mostly smaller than 100 arc seconds using the estimated BC values from the new method - significantly smaller than prediction errors obtained using other BC estimations. © 2013 COSPAR. Published by Elsevier Ltd. All rights reserved.


Sang J.,EOS Space Systems Pty Ltd | Smith C.,EOS Space Systems Pty Ltd | Zhang K.,RMIT University
AIAA/AAS Astrodynamics Specialist Conference 2012 | Year: 2012

This paper presents a method of estimating atmospheric mass densities from precise orbit data of low earth orbit (LEO) space objects. The method is based on the drag perturbation equation of the semi-major axis of the orbit of LEO space objects which relates the change rate of the semi-major axis to the atmospheric mass density. The feasibility of applying the method is studied with simulations. The method is experimented using the GFZ-ISDC GPS rapid science orbit (RSO) products of the CHAMP satellite over a time period of three months. The densities from this method and accelerometer are compared and good agreements are achieved. This method has a great potential to generate high quality atmospheric mass densities with a high temporal resolution for LEO satellite missions. © 2012 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.


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 | Year: 2010

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.


Smith C.,EOS Space Systems Pty Ltd
Advances in the Astronautical Sciences | Year: 2012

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.


Sang J.,EOS Space Systems Pty Ltd | Smith C.,EOS Space Systems Pty Ltd
AIAA/AAS Astrodynamics Specialist Conference 2012 | Year: 2012

EOS Space Systems conducted a demonstration project of optically tracking geostationary and high altitude satellites using CCD camera on its 1.8m telescope located at its Mt Stromlo Space Research Centre in August 2006. The images of the tracked satellite and stars were processed in real time. First, the stars in images were identified using UCAC2 catalog. The rotation and scale parameters of transforming the camera pixel system to azimuth/elevation system were then estimated from the positions of the identified stars. And finally, the azimuth and elevation of the tracked object were determined using transformation parameters and positions of the identified stars. The experiments showed that such a system could complete the tracking of a geostationary satellite within 2-3 minutes including the telescope slewing time, and generate, on average, between 40-80 normal point positions of the tracked object. The accuracy of the generated azimuth and elevation observations was shown better than 1 arc second. © 2012 by the American Institute of Aeronautics and Astronautics, Inc.


Sang J.,EOS Space Systems Pty Ltd | Smith C.,EOS Space Systems Pty Ltd
AIAA/AAS Astrodynamics Specialist Conference 2012 | Year: 2012

The EOS Space Debris Tracking System (SDTS), located at Mt Stromlo, Canberra, demonstrated the capability of laser tracking of LEO space debris objects in two projects. The first project, the RazorView project carried out in July and August 2004, showed that the system was able to track the objects of known TLE elements. The second object, the NEOT project in August and September 2005, demonstrated that the system could acquire debris objects of unknown orbit information by laser signals. This paper presents a performance assessment of the system through an analysis of the observations collected from the two projects. It is shown that the RMS errors of the observations are about 1.5m for the laser ranging data, and about 1.5; for the angular directions, respectively. It also shows that an object newly-acquired by the laser tracking could be reacquired using a wide field of view camera (3 degrees field of view) in about 36 hours. © 2012 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

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