Michael Lachut

The global electro-optical (EO) and laser tracking sensor network was considered to investigate improvements to orbit prediction (OP) accuracy of space debris by combining angle and laser ranging data. However, it is worth noting that weather, schedule and visibility constraints can frequently limit the operations of such sensors, which may not result in sufficient tracking data for accurate OP. In this study, several 1-day OP results for low Earth orbit (LEO) space debris targets were demonstrated under a limited observation environment to verify the OP accuracy through the combination of angle and laser ranging data from two sites. For orbit determination (OD) processes, it was considered to analyze the OP accuracy by one site providing both 2–day arc angle data and 1-day arc laser ranging data, while the other was limited to 1-day arc angle data. In addition, the initial ballistic coefficient ( B C ) application method was proposed and implemented for the improvement of OD/OP acc...

One of the primary aims of the Space Environment Research Centre (SERC) is to build and maintain its own catalogue of objects in near-Earth orbits. This will provide accurate ephemeris data for object acquisition in both passive and active tracking, covariance matrices for sensor schedule tasking and observation correlation, state and uncertainty propagation for conjunction assessments, and help facilitate the remote maneuver of debris using high powered lasers delivered from ground stations, which is the primary objective of SERC. The catalogue comprises objects which pose a threat of colliding with Optus satellites identified in conjunction assessments, potential candidates for the laser maneuver, and other objects of interest for ongoing research including Envisat, Topex, small cubesats, and HAMR debris. In this paper, we will present methods to automate the assessment of orbit predictions and estimations to maintain and build a new catalogue of space assets and debris. The proce...

This paper reports the progress of the development of a new conjunction and threat warning service for satellite operators and a laser manoeuvre demonstration. The status and characteristics of the network of sensors being used is described and the progress of the space situational awareness service being developed is provided along with a timeline for full operational capability. The construction of a new site in Learmonth Western Australia – a joint venture between EOS Space Systems and Lockheed Martin, with support from the Australian Department of Defence – sees new optical and laser ranging systems installed to supplement EOS’s existing site at Mt Stromlo, Canberra. Four telescopes have been installed at Learmonth: two 1-metre laser beam directors and two 0.7 metre Deep Space Trackers. The installation of a 0.7 metre Deep Space Tracker by EOS Space Systems for the Space Environment Research Centre (SERC) at Mount Stromlo, supplements EOS’s existing 1.8 metre Space Debris Tracki...

The Space Environment Research Centre (SERC) is building a space object catalogue to provide accurate and reliable orbital information for a number of applications. Orbital elements are generated by fitting optical and laser tracking data from tracking assets located in Australia. This paper reports on the orbital prediction accuracy achieved. The data processing and fusion methodologies are described that improve accuracy and ensure the orbit determination process is not corrupted by erroneous data. Additional information from the data is also obtained by estimating the rates of change of the observation arcs. When the angles and range observation data are fused, the accurate 6-dimensional data is used to generate state vectors directly from the observations. The orbit prediction improvements form a critical component of a Conjunction Assessment capability that is being developed and the progress of the automatic generation of orbit elements is reported here.

The well-known cannonball model has been used ubiquitously to capture the effects of atmospheric drag and solar radiation pressure on satellites and/or space debris for decades. While it lends itself naturally to spherical objects, its validity in the case of non-spherical objects has been debated heavily for years throughout the space situational awareness community. One of the leading motivations to improve orbit predictions by relaxing the spherical assumption, is the ongoing demand for more robust and reliable conjunction assessments. In this study, we explore the orbit propagation of a flat plate in a near GEO orbit under the influence of solar radiation pressure, using a classical Lambertian BRDF model. Consequently, this approach will account for the spin rate and orientation of the object, which is typically determined in practice using a light curve analysis. Here, simulations will be performed which systematically reduces the spin rate to demonstrate the point at which the...

Nanomechanical doubly-clamped beams and cantilever plates are often used to sense a host of environmental effects, including biomolecular interations, mass measurements, and responses to chemical stimuli. Understanding the effects of surface stress on the stiffness of such nanoscale devices is essential for rigorous analysis of experimental data. Recently, we explored the effects of surface stress on cantilever plates and presented a theoretical framework valid for thin plate structures. Here, we generalize this framework and apply it to cantilever plates and doubly-clamped beams, exploring in detail the relative physical mechanisms causing a stiffness change in each case. Specifically, Poisson’s ratio is found to exert a dramatically different effect in cantilevers than in doubly-clamped beams, and here we explain why. The relative change in effective spring constant is also examined, and its connection to the relative frequency shift is discussed. Interestingly, this differs from ...

Numerous measurements have indicated that surface stress can significantly modify the stiffness of cantilever sensors. In contrast, theoretical calculations using classical beam theory predict that stiffness is independent of surface stress. Using a three-dimensional analysis, we recently showed that surface stress does indeed have an effect within the framework of linear elasticity. However, only cantilevers of rectangular geometry were explored. Here, we vary cantilever geometry and find that it plays a critical role, with V-shaped cantilevers displaying greatly enhanced sensitivity in comparison to rectangular cantilevers. Tuning cantilever geometry therefore provides a sensitive route to controlling the effects of surface stress.