objects with mass larger than 10-3 g generated by past space activities and .... 7328.0 0.0014 82.60 1360.0 0.7493 0.125 0 1990 2310 Tsyklon LVFS.
CONSORZIO PISA RICERCHE
FINAL REPORT
SPACE DEBRIS MITIGATION EXTENSION OF THE SDM TOOL L. Anselmo, A. Cordelli, C. Pardini and A. Rossi
ESA/ESOC Contract No. 13037/98/D/IM ESA/ESOC Technical Supervisor: R. Jehn European Space Agency Contract Report
________________________________________________ The work described in this report was done under ESA contract. Responsibility for the contents resides in the authors that prepared it.
________________________________________________
Pisa, 5 May 2000
TABLE OF CONTENTS
1.0 INTRODUCTION _______________________________________________________ 3 2.0 SOFTWARE DESCRIPTION ______________________________________________ 6 2.1 Review of New Mitigation Options _____________________________________________ 6 2.2 Explosions _________________________________________________________________ 8 2.3 Collisions __________________________________________________________________ 9 2.4 Generation of Debris Clouds from Explosions and Collisions ______________________ 10 2.5 RORSAT-like Events _______________________________________________________ 10 2.6 Traffic Model ______________________________________________________________ 11 2.7 Retrievals _________________________________________________________________ 15 2.8 Propagation of the Running Population ________________________________________ 15 2.9 Simulation Management_____________________________________________________ 15
3.0 MODEL FOR THE INITIAL POPULATION ________________________________ 17 3.1 Fragmentation Models ______________________________________________________ 18 3.2 Low Intensity Explosions ____________________________________________________ 18 3.3 High Intensity Explosions____________________________________________________ 18 3.4 Collisions _________________________________________________________________ 19 3.5 RORSAT Liquid Metal Leakage ______________________________________________ 19 3.6 Area-to-Mass Ratio _________________________________________________________ 22 3.7 Fragment Velocity Distribution _______________________________________________ 22 3.8 Debris Propagation _________________________________________________________ 23 3.9 Orbital Breakups __________________________________________________________ 24 3.10 Breakup Classification _____________________________________________________ 24 3.11 Fragmentation Events Included in the New Population __________________________ 25 3.12 Catalogued Objects ________________________________________________________ 30 3.13 The New Orbital Debris Population __________________________________________ 32 3.14 Population Files Structure __________________________________________________ 33 3.15 Comparison with Other Models _____________________________________________ 35
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4.0 LONG-TERM ANALYSIS OF DEBRIS MITIGATION MEASURES _____________ 37 4.1 Comparison with DERA _____________________________________________________ 37 4.2 Sensitivity Analysis of the De-orbiting Option ___________________________________ 39 4.3 Simulation Time Span ______________________________________________________ 39 4.4 Monte Carlo Runs __________________________________________________________ 39 4.5 Initial Population __________________________________________________________ 39 4.6 Explosion Events ___________________________________________________________ 39 4.7 Low Intensity Explosions ____________________________________________________ 40 4.8 High Intensity Explosions____________________________________________________ 40 4.9 Collisions _________________________________________________________________ 40 4.10 RORSAT Liquid Metal Leakage _____________________________________________ 41 4.11 Fragment Velocity Distribution ______________________________________________ 41 4.12 Area-to-Mass Ratio ________________________________________________________ 42 4.13 Orbital Propagation _______________________________________________________ 42 4.14 Traffic Model _____________________________________________________________ 42
5.0 SIMULATION RESULTS ________________________________________________ 44 5.1 Long-Term Evolution Scenarios ______________________________________________ 44 5.2 Discussion of the Results in LEO ______________________________________________ 44 5.3 Results in GEO ____________________________________________________________ 45 5.4 Results in Earth Orbit up to 40,000 km ________________________________________ 54 5.5 Comparison with DERA Simulation Results ____________________________________ 54
6.0 REFERENCES ________________________________________________________ 59
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1.0 INTRODUCTION
The Space Debris Mitigation long-term analysis program (SDM, Version 2.0) has been developed to study the long-term evolution of orbital debris and to evaluate the effectiveness of mitigation measures. It is applicable in circumterrestrial space up to 40,000 km of altitude (i.e. the GEO regime is included) and for debris with mass larger than 1 mg (corresponding, for the most used area-to-mass relations, to just less than 1 mm). The flow chart of the software is shown in Figure 1.1. The software was developed for UNIX machines and exploits the file system structure of such an operative system. Apart from this, it is fully computer independent, since it does not use any library routine. All the code is written in FORTRAN 77 [Cordelli, 2000]. SDM 2.0 represents a substantial upgrade of SDM 1.0, developed in the framework of a previous ESOC contract [Anselmo et al., 1996]. It maintained the original philosophy of a debris population subdivided in the historical and running components, whose combination gives the background population used for collision rate computations. This choice was motivated by the need of reasonable memory allocation and CPU time for tens of Monte Carlo runs spanning one century or more. However, the future traffic and mitigation practices models, already quite detailed and sophisticated in SDM 1.0, were modified to include even more elaborate and intricate scenarios. In particular, realistic de-orbiting and re-orbiting options were added, both in LEO and in GEO [Cordelli and Rossi, 2000]. The aim of SDM is to follow, as much as possible, the actual orbital evolution of space objects. Therefore, for the large ones, each orbit is individually propagated with a fast Debris Cloud Propagator (DCP) [Anselmo et al., 1996]. However, due to the very large number of small debris involved in the problem, some simplifying assumptions had to be introduced. In particular, it was not realistic to propagate all these particles individually; then, a sampling was introduced and only representative particles were propagated. The objects modeled by SDM are divided in two categories. The objects present in space at the start of a simulation belong to the so called historical population. It is composed by all the objects with mass larger than 10-3 g generated by past space activities and catastrophic events (explosions, collisions, RORSAT's cooling fluid leaks, etc...). This population can be obtained from any suitable existing model, like ESA's MASTER or CODRM-99, developed in the framework of this contract.
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GENERAL INPUT
START
HISTORICAL POPULATION DENSITIES
step 0
SETUP DENSITIES FOR BACKGROUND POPULATION
CHECK S/C END-OF-LIFE DISPOSAL OPTIONS
EXPLOSION PROBABILITY DATA
NEW BACKGROUND POPULATION DENSITIES
step n
YES
EXPLOSION ?
GENERATE FRAGMENTS N(M), A/m, V
NO COMPUTE DEBRIS ORBIT a, e, i
COMPUTE COLLISION PROBABILITY P(m 1 ,m 2 ,h)
COLLISION PROBABILITY DATA V(h)
YES
COLLISION ?
GENERATE FRAGMENTS N(M), A/m, V
NO COMPUTE DEBRIS ORBIT a, e, i GENERATE NEW PAYLOADS, UPPER STAGES AND OPERATIONAL DEBRIS
LAUNCHES DATA
PROPAGATION OF RUNNING POPULATION t->t+t
DCP
COMPUTE DENSITIES FOR RUNNING POPULATION
RETRIEVAL DATA
ADD HISTORICAL POPULATION AND REMOVE RETRIEVALS
COMPUTE DENSITIES FOR NEW BACKGROUND POPULATION
t= t+ t
YES
t
