Effect of thermospheric contraction on remediation of the near-Earth space debris environment

Historically, computer simulations of the near-Earth space debris environment have provided a basis for international debris mitigation guidelines and, today, continue to influence international debate on debris environment remediation and Active Debris Removal (ADR). Approximately 22,500 objects larger than 10 cm are known to exist in Earth orbit and less than 5% of these are operational payloads, with the remaining population classed as space debris. These objects represent a significant risk to satellite operations, due to the possibility of damaging or catastrophic collisions, as demonstrated by the collision between Iridium 33 and Cosmos 2251 in February 2009. Indeed, recent computer simulations have suggested that the current population in low Earth orbit (LEO) has reached a sufficient density at some altitudes for collision activity there to continue even in the absence of new launches. Even with the widespread adoption of debris mitigation guidelines, the growth of the LEO population, in particular, is expected to result in eight or nine collisions among catalogued objects in the next 40 years. With a new study using the University of Southampton’s space debris model, entitled DAMAGE, we show the effectiveness of debris mitigation and removal strategies to constrain the growth of the LEO debris population could be more than halved due to a long-term future decline in global thermospheric density. However, increasing debris remediation efforts can reverse the impact of this negative density trend

The fast debris evolution model

The ‘Particles-in-a-box’ (PIB) model introduced by Talent (1992) removed the need for computer-intensive Monte Carlo simulation to predict the gross characteristics of an evolving debris environment. The PIB model was described using a differential equation that allows the stability of the low Earth orbit (LEO) environment to be tested by a straightforward analysis of the equation’s coefficients. As part of an ongoing research effort to investigate more efficient approaches to evolutionary modelling and to develop a suite of educational tools, a new PIB model has been developed. The model, entitled Fast Debris Evolution (FADE), employs a first-order differential equation to describe the rate at which new objects ?10 cm are added and removed from the environment. Whilst Talent (1992) based the collision theory for the PIB approach on collisions between gas particles and adopted specific values for the parameters of the model from a number of references, the form and coefficients of the FADE model equations can be inferred from the outputs of future projections produced by high-fidelity models, such as the DAMAGE model. The FADE model has been implemented as a client-side, web-based service using JavaScript embedded within a HTML document. Due to the simple nature of the algorithm, FADE can deliver the results of future projections immediately in a graphical format, with complete user-control over key simulation parameters. Historical and future projections for the ?10 cm low Earth orbit (LEO) debris environment under a variety of different scenarios are possible, including business as usual, no future launches, post-mission disposal and remediation. A selection of results is presented with comparisons with predictions made using the DAMAGE environment model. The results demonstrate that the FADE model is able to capture comparable time-series of collisions and number of objects as predicted by DAMAGE in several scenarios. Further, and perhaps more importantly, its speed and flexibility allows the user to explore and understand the evolution of the space debris environment<br/

Cloud computing for planetary defense

In this paper we demonstrate how a cloud-based computing architecture can be used for planetary defense and space situational awareness (SSA). We show how utility compute can facilitate both a financially economical and highly scalable solution for space debris and near-earth object impact analysis. As we improve our ability to track smaller space objects, and satellite collisions occur, the volume of objects being tracked vastly increases, increasing computational demands. Propagating trajectories and calculating conjunctions becomes increasingly time critical, thus requiring an architecture which can scale with demand. The extension of this to tackle the problem of a future near-earth object impact is discussed, and how cloud computing can play a key role in this civilisation-threatening scenari

The space debris environment: future evolution

Space debris represents a significant risk to satellite operations, due to the possibility of damaging or catastrophic collisions. Consequently, many satellite operators screen the orbiting population for close approaches with their on-orbit assets and a public conjunction assessment service, Satellite Orbital Conjunction Reports Assessing Threatening Encounters in Space (SOCRATES), generates close approach predictions on a daily basis for all satellite payloads in the catalogue. These screening capabilities are used to inform operational decisions relating to risk mitigation but it is anticipated that the demands placed on these services will increase as debris becomes more prolific. This hypothesis is explored in a preliminary analysis of conjunction data for the years 2004 to 2009 and a new ‘Business As Usual’ study using the Debris Analysis and Monitoring Architecture for the Geosynchronous Environment (DAMAGE) model. The results suggest a 50% increase in the number of close approaches reported by SOCRATES (or its equivalent) within the next ten years. By 2059, daily conjunction reports could contain over 50,000 close approaches below 5 km, affecting the demands placed on tracking facilities and satellite resources

The implementation of cost effective debris protection in unmanned spacecraft

Proper characterisation of the survivability of an unmanned spacecraft to debris impact must go beyond just a simple assessment of the probability of penetration. Some penetrative damage may be survivable, particularly if critical internal equipment is arranged judiciously. Consideration of the satellite architecture can be seen as a potentially cost-effective and complementary approach to the more traditional method of adding shielding mass. To quantify the benefits of both strategies, and identify candidate protection solutions for a typical satellite design, a new model called SHIELD has been developed. Competing protection options are evaluated using a survivability metric. Rapid convergence on one or more ‘good' designs can also be achieved with a built-in genetic algorithm search method. SHIELD's potential as a project support tool is illustrated by applying it to the survivability evaluation of a satellite currently under design. The effectiveness of the genetic algorithm is also demonstrated, but on a more idealised spacecraft design