Debris Environment Research Articles

A New Orbital Debris Reference Model

This paper presents a new orbital debris environment model (CODRM-97). It includes the objects with a mass ≥ 1 mg produced by international space launches and operations, 140 energetic breakups and 16 liquid metal coolant leaks from nuclear-powered spacecraft. Each fragmentation or leakage was simulated with the most appropriate models and parameters, and the resulting debris clouds were propagated, including all the significant orbital perturbations, to the chosen reference epoch (January 1, 1997). At this point, the particles still in orbit were merged with the cataloged objects present in space at the same time. In total, more than 65 million particles with a mass ≥ 1 mg were generated during the simulations and more than 52 million were found to be still in orbit at the reference epoch. Preliminary comparisons with the measurements available below 1000 km seem to indicate that the CODRM-97 predictions come short by a factor of two for debris with diameters close to 1 cm and by an order of magnitude for particles with diameters approaching 1 mm. This deficiency might reflect, in part, an intrinsic inadequacy of the breakup models adopted, but probably suggests the presence in space of additional debris sources, not yet included in CODRM-97.

The influence of the fragmentation threshold on the long term evolution of the orbital debris environment

By means of the code STAT, developed in the past four years in Pisa under an ESA contract, we have carried out a number of numerical simulations of the long term evolution of the orbital debris population, and monitored the growth in time of the number of objects larger than 1 mg in mass. Previous work had shown that after a phase of gradual, quasi-linear growth due to launches and explosions, collisions in the low-orbit population lead to a kind of a chain reaction, yielding a runaway proliferation of fragments. The epoch at which this behavior takes place as well as the characteristic time constant of the nearly-exponential growth phase are sensitively related to some parameters of the physical model adopted for the collisional outcomes. The most critical of such parameters is the fragmentation threshold Q ∗ , defined as the limiting value of the ratio between the projectile kinetic energy and the target mass which discriminates between small scale “cratering” impacts and disruptive collisions. Here we report on the results of a set of simulations performed by varying Q ∗ by plus or minus a factor two with respect to the nominal value of 4.5 × 10 4 J/kg, inferred from laboratory experiments. The main results of these simulations are the following: first, we confirm that a phase of nearly-exponential runaway growth of the small-size debris population is always observed, but the initial “waiting time” interval is at least ≈ 200 years for our range of Q ∗ values: second, the onset time for the exponential regime as well as its characteristic time constant are growing functions of Q ∗ ; and third, this behavior agrees well with the forecasts of much simpler mathematical models developed earlier (Farinella and Cordelli, Science & Global Security 2, 365–378, 1991). Our results highlight the need for more extensive experimental estimates of the fragmentation threshold parameter and its dependence on the size, shape and structure of the space objects. Such estimates should then be incorporated into a future generation of more realistic simulation models.

11. The Space Debris Environment of the Earth, Amounts and Growth

11. The Space Debris Environment of the Earth, Amounts and Growth

Correlation of spacecraft anomalies to the debris environment: an update

The development of debris environment analysis tools and correlation of space weather with satellite anomalies have progressed nearly independently during the space age. This paper applies a methodology to merge these two fields to provide greater insights into the operation of satellites in the dynamic space environment. The objective of this analysis is to corroborate the impact of debris on spacecraft while identifying the cause of previously “unknown” anomalies. This approach is used to reduce a select anomalies database and make conclusions about the cause of many previously unknown anomalies. A new concept is proposed that collates multiple anomalies data bases into a Universal Satellite Anomalies Analysis Advisor (USA 3).

Probabilistic assessment of debris impact damage on orbital structures

Stochastic models of damage caused by man-made debris impacts on orbital structures are developed. Randomness in characteristics of debris objects and the target body are considered. The debris impacts are modeled as Poisson events in time and space. In a first model, the effect of damage accumulation (coinciding impact craters) is included and the statistical moments of the damage random field are derived. Numerical investigations show, however, that for typical space flights and debris environments the accumulation effect is negligible. Based on this finding, a simpler model is developed that neglects the accumulation of damage, but is able to provide statistics on the size of damage. The probability distribution of the size of the largest crater inflicted on the surface of a spacecraft during one or more flight segments is derived based on this model.

Debris families observed by the haystack orbital debris radar

The Haystack radar provides a unique capability to observe and monitor the orbital debris environment in low-Earth orbit for debris sizes down to less than 1 cm in diameter. Recent changes in the observation geometry of the Haystack radar have greatly enhanced the capability of the radar in separating debris objects into orbit families. Using this capability, it is possible to identify specific families of debris based on inclination and altitude regimes. The radar measurements can then be used to obtain size distributions and polarization characteristics of the debris in the families. Using this method, one previously unrecognized debris family in 65° inclination circular orbits between 850 and 1000 km altitude has been tentatively identified as the leaking sodium–potassium coolant from Russian RORSAT reactors. Debris from specific breakups have also been identified, such as from the breakups of Cosmos 1275 and Cosmos 1484. This ability to assign some debris objects to specific sources opens up new possibilities in studying the nature and causes of breakup events.

Synergistic use of debris environment models for flexible, very-long term projections

Long-term debris environment projections are of great importance for assessing the necessity and effectiveness of debris mitigation measures. Two types of models have been developed to predict these environments. Environment evolution models like the EVOLVE code are using detailed mission model data to input spacecraft, upper stages, and operational debris into specific orbits at specific times; debris from fragmentations are placed in orbits defined by the state vector of the fragmenting object(s) and the breakup model. The second type, typified by the CHAIN program, uses a particle-in-box model that bins the environment in size and altitude rather than following the orbit evolution of individual debris fragments. A 3-Step approach using both the EVOLVE and CHAIN model in a synergistic way was used to increase the reliability of long term environment projections. EVOLVE historical projections 1957–1995 could be validated by comparison to measurements. The comparison of 100 year projection runs of EVOLVE and CHAIN for different traffic scenarios showed a good agreement. In this paper, for the first time, CHAIN projections up to 10,000 years, based on validated boundary conditions derived by EVOLVE are presented, indicating clearly the need of early implementation of effective mitigation measures to prevent exponential population growth by collisional cascading effects.

Space Debris Issue at the United Nationsa

ABSTRACT: The space debris issue has been discussed by the United Nations Committee on the Peaceful Uses of Outer Space (COPUOS) for many years. In recognition of its importance, at the 1994 session of the Scientific and Technical Subcommittee of COPUOS, it became a separate agenda item. The Committee agreed that international cooperation is needed to evolve appropriate and affordable strategies to minimize the potential impact of space debris on future space missions. This paper summarizes discussions held during the last two sessions of the Subcommittee, including inter alia space debris measurement techniques, mathematical modelling of the debris environment, characterizing the space debris environment, and spacecraft design measures to protect against space debris. The focus of the 1995 session was on the subject of acquisition and understanding of data on the characteristics of the space debris environment, which is closely related to the observations of NEO.

Lessons learned from the comparison of EVOLVE and CHAIN

EVOLVE and CHAIN are two models for the projection of the orbital debris environment. They were developed independently using very different conceptual approaches. Consequently, their comparison has proven to be valuable for validating the debris environment projections for both programs. The project to use EVOLVE and CHAIN to validate one another and to develop a complementary use of the two codes has been documented in a series of papers. The early papers in this series were focused on a comparison of results for environment projections over the next 100 years. These comparison produced relatively minor changes (and improvements) in both programs that could be explained by conceptual differences designed into the original codes. Later papers in the series focused on using EVOLVE to establish rate coefficients to be used by CHAIN for longer term environment projections. In this paper we will review the new understandings that have resulted from these efforts. We will also extend the work on establishing an improved method for using EVOLVE to set conditions for long-term CHAIN environment projections and use this new work to begin investigating the sensitivity of the environment projections to aspects of collisional breakup models that currently are, and in the foreseeable future will continue to be, severely short of data.

Simulation and modelling of orbital debris environment by equivalent breakups

It is well known that the increasing space activities pose a serious threat to future missions. This is mainly due to the presence of spent stages, rockets spacecraft and fragments which can lead to collisions. The calculation of the collision probability of future space vehicles with the orbital debris is necessary for estimating the risk. There is lack of adequately catalogued and openly available detailed information on the explosion characteristics of trackable and untrackable debris data. Such a situation compels one to develop suitable mathematical modelling of the explosion and the resultant debris environment. Based on a study of the available information regarding the fragmentation, subsequent evolution and observation, it turns out to be possible to develop such a mathematical model connecting the dynamical features of the fragmentation with the geometrical/orbital characteristics of the debris and representing the environment through the idea of equivalent breakup.

Radar cross sections and ballistic coefficients of fragments from impacts with complex, full-scale targets

Debris fragments from impacts of complex, full-scale projectiles and targets were characterized by radar cross section (RCS) and ballistic coefficient. Results from RCS measurements using a compact range and ballistic coefficient measurements using a drop tower are presented with correlations to fragment size, shape, area, and mass properties. Such correlations support the development of debris environment models and can also be used to determine other fragment properties from observations of RCS or aerodynamic deceleration. The applicability of these data and models to impacts at higher velocities is also addressed.

The long-term implications of operating satellite constellations in the low earth orbit debris environment

DRA's Integrated Debris Evolution Suite (IDES) model is used in this study to predict the future evolution of the orbital debris environment for two distinct scenarios. For the first case, a pre-generated background debris population for 1995 and ‘business as usual’ future launch/explosion rates are used as input to the model. IDES then employs its collision event prediction algorithm to simulate evolution from 1996 to 2020 as a baseline. The second scenario uses the same initial conditions and future trends, but in addition, a large constellation is introduced into the simulation process from year 1998 onwards. The additional contribution of the constellation to the temporal variation of key environment/population parameters is presented; including enhancement from any long-term collision coupling effects.

Long term evolution of the space debris population

In the last few years two different computer models have been developed in Pisa to study the evolution of the debris population. With them it is possible to simulate different scenarios for the future launch policies. We have defined a reference case which is a reasonable forecasting of the future space activities. Based upon it we have performed a number of simulations to study the influence of the initial population on the long-term evolution of the debris environment. Moreover, we have analyzed the sensitivity of the models upon the different parametrizations of the physical processes involved in order to highlight the main areas of uncertainty which may affect the long term predictions.

Concepts and applications of the MASTER space debris environment model

In 1995 ESA released a β-version of their meteoroid and space debris terrestrial environment reference model (MASTER). On a single CD ROM the MASTER release provides all documentation, data, and executables to perform debris and meteoroid flux analysis for earth orbiting spacecraft on a large range of computer platforms. In its high resolution mode the software can be used for a detailed discrimination of flux contributions from historic on-orbit fragmentation events or from sporadic meteoroids for any target orbit from LEO to GEO altitudes. The MASTER model is based on quasi-deterministic principles with comprehensive orbit propagation theories and volume discretisation techniques to derive spatial densities and velocity distributions in a 3D control volume between LEO and GEO altitudes. Debris flux results are discussed for a sun-synchronous LEO and for a highly eccentric GTO orbit.

The terrestrial particulate environment and its future evolution

In this paper an overview over the current space debris situation is given. With the help of ESA's new Meteoroid And Space Debris Terrestrial Environment Reference (MASTER) model, the spatial density of space debris is calculated as function of altitude and latitude. Statistical information about collision risk and collision velocities is presented. In order to estimate the ratio of debris to meteoroid impacts on the surfaces of returned hardware from space (LDEF, Hubble Space Telescope solar array and EuReCa) a state-of-the-art meteoroid model is required. At the Max-Planck-Institute in Heidelberg the meteoroid model of Neil Divine was enhanced and implemented in a software programme used at ESOC for meteoroid flux predictions on satellite surfaces. Finally, using the models of the current environment as initial conditions an attempt is made to predict the future evolution of the space debris environment. Two models using different approaches are considered: CHAINEE, a particle-in-the-box model and SDM, a semi-deterministic model. Both models are used to study the effectiveness of debris mitigation measures.

Impact of satellite constellation arrangement on the future orbital debris environment

The proposed concept of communication satellite constellation such as Iridium (with 66 satellites) and Teledesic (with 840 satellites) in LEO has been studied for its operational constrains and the impact to the evolution of the future orbital debris environment. A large number of spacecraft in constellation creates a spike in spatial density distribution at a place where they are collocated in a thin shell, which in turn increases the collision probability with other space objects passing through the thin shell. Once a collision has occurred, most of the collision fragments and the damaged spacecraft will drift in the vicinity of the thin shell and further increase the mutual collision rate for the objects in the shell. This cascading effect is not only devastating to the operation of communication satellites in a constellation, but also has a significant impact on the evolution of the future orbital debris environment. Model calculations with a constellation of 1000 satellites at 600, 800, 1000 or 1500 km altitude are used to examine the fate of the satellites in the constellation and assess the impact on the orbital debris environment following the event. It is found that the optimal operational condition for these constellation satellites is to have a small cross-sectional area and for the constellation to be placed at an altitude region away from high concentrations of current space objects.

Orbital debris: a technical assessment

To acquire an unbiased technical assessment of (1) the research needed to better understand the debris environment, (2) the necessity and means of protecting spacecraft against the debris environment, and (3) potential methods of reducing the future debris hazard, NASA asked the National Research Council to form an international committee to examine the orbital debris issue. The committee was asked to draw upon available data and analyses to: characterize the current debris environment, project how this environment might change in the absence of new measures to alleviate debris proliferation, examine ongoing alleviation activities, explore measures to address the problem, and develop recommendations on technical methods to address the problems of debris proliferation.

Basic science in knee arthroplasty

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Space Debris

AbstractMan-made, artificial space debris is of interest to the study of interplanetary dust for two reasons: (1) In many regions of Earth orbital space, the space debris flux is larger than the natural meteoroid flux, complicating the study of interplanetary dust, and (2) models and experiments developed to understand space debris may have application to the study of interplanetary dust. The purpose of this paper is to summarize the space debris environment as it is understood today by characterizing the models used to predict the space debris environment and describing the measurements to test the model predictions.Within the last 5 years, the space debris environment has been measured by a number of experiments. These experiments have revealed significant sources of debris in addition to the assumed major source of satellite explosions. Understanding these sources has required the development of more complex models and additional insight into the design and operation of spacecraft. Increased awareness of space debris issues at an international level has led to measures that have reduced the rate of growth in the environment. However, the number of new debris sources discovered seems to be proportional to the number of new measurements of the environment.

A comparison of debris environment projections using the evolve and chain models

EVOLVE and CHAIN are two models for debris environmen, projections that have been developed independently using very different conceptual approaches. A comparison of results from these two models therefore provides a means of validating debris environment projections which they have made. EVOLVE/1/ is a model that requires mission model projections to describe future space operations; these projections include launch date, mission orbit altitude and inclination, mission duration, vehicle size and weight, and classification as an object capable of experiencing breakup from on-board stored energy. EVOLVE describes the orbital debris environment by the orbital elements of the objects in the environment. CHAIN /2,3/ is an analytic model that bins the debris environment in size and altitude rather than following the orbit evolution of individual debris fragments. The altitude/size bins are coupled by the initial spreading of fragments by collisions and the following orbital decay behavior. A set of test cases covering a variety of space usage scenarios have been defined for the two models. In this paper, a comparison of the results will be presented and sources of disagreement identified and discussed. A sensitivity analysis of the most important model components will be performed using both models.