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CLOSE APPROACH PREDICTION ANALYSIS OF THE EARTH SCIENCE CONSTELLATION
WITH THE FENGYUN-1C DEBRIS
Matthew Duncan - a.i. solutions, Inc. Colorado Springs, CODavid Rand - a.i. solutions, Inc. Lanham, MD
Goddard Space Flight Center Mission Operations and Mission Services/
Flight Dynamics Analysis Branch
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Agenda
► Overview and Goals
» Recent and Current Orbital Debris population
» Earth Science Constellation
» Earth Science Constellation and the Fengyun-1C Debris
► Long Term Prediction Method
» Easy High Performance Computing (HPC)
» Our solution in detail
» Process details
► Prediction Results
► Future Work
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2000 - Cataloged objects >10 cm diameter
Images courtesy NASA Orbital Debris Program Office
Recent Debris Population
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March 2007 - Tracked objects >10 cm diameter (FENGYUN-1C Debris in red)
Images courtesy NASA Orbital Debris Program Office
Current Debris Population
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► The collision risk due to orbital debris is increasing:» ~14,000 tracked objects >1 cm2
» Several hundred objects added to catalog each year (Ref. Liou & Johnson)► SFC Earth Observing assets reside in one of the most congested orbital regimes:
» Sun-synchronous “EOS” orbit - 11 Earth Science Assets (Aqua, Aura, Terra PARASOL, CloudSat, CALIPSO, ICESat, Landsat-5, Landsat-7, EO-1, SAC-C)
Debris Environment
0 200 400 600 800 1000 1200 1400 1600 18000
100
200
300
400
500
600
700
Mean Equatorial Height(km)
Nu
mb
er
of
Ob
jects
(pe
r 2
0 k
m b
in) Low Earth Orbit Height Distribution - Nov 2007
Catalog - TotalFengyun-1C Deb
EOS Orbit
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Earth Science Constellation (ESC)
► Combination of NASA and Foreign assets
► Each mission makes its own risk mitigation decisions
► Each mission subject to own maneuverability, comm., and ops concept constraints
► All missions will see similar debris issues
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Current ESC Debris Trends
► Debris Screening performed every week day, 7 days into the future for each ESC mission against entire debris catalog
► Chinese ASAT Test occurred Jan. 11, 2007 generating over 2200 tracked objects to date
» by the end of Feb. 2007 all ESC missions had at least one conjunction event with ASAT debris
► ESC currently sees about 70 conjunctions per month, per spacecraft within a 2x25x25km (RIC) monitor volume
» 10-15% of these conjunctions are now Fengyun-1C
► Currently, 92% of Fengyun-1C debris still above ESC altitude in a very similar orbit geometry
» How this population decays and impacts the ESC orbit regime is of critical importance
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► Predict increase in conjunction events due to decay into ESC
» Predict the ESC Assets into the future
» Predict debris states into the future
» Calculate conjunction rates between both groups
► Numerically propagate 2200+ debris objects for 20 years
» Lots of processing time
» 20 years of conjunction comparison is more processing time
► Require a means to perform processing in less time
» High performance computing
» Windows platform
Measure the Impact to the ESC
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► Microsoft® Windows® Compute Cluster Server 2003 (CCS2003)
» Released in Mid 2006
► Key Features:
» Windows environment – a first in high performance computing; dominated by Linux to date
» Integrated job scheduler – spread multiple tasks to all available nodes automatically
» Parallel processing capability – supports specialized parallel problems
» Easy setup – more so than open source solutions; hours vs. days
» Integrates to existing network
Windows and HPC
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► Compute Cluster Server 2003
» Comfortably runs on inexpensive commodity hardware
» Relies on MS Active Directory network architecture
» Head node + several compute nodes
» Work submitted in a “job” made up of individual “tasks”
• A “task” is a single command line call to an executable
► FreeFlyer® mission analysis software
» GUI and command line interfaces
» Extensive database and file interface capabilities
» Native Windows application
► Extremely simple and easy to setup network topology
Our HPC Environment
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HeadNode CN01 CN02 CN03 CN04 CN05
Gigabit Switch
Corp. NetworkMonitor, Keyboard, Mouse on HeadNode
HPC Cluster Typical Configuration
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Problem: Using states of over 2200 objects, contained in a MySQL database, propagate each for 20 years and compare against ESC
Process:1. Create Representative ESC asset ephemeris data
» Three representative orbits (Aqua, Aura, Terra)2. Obtain states from database and build Ephemeris job template
» Each task is one 20 year propagation 3. Submit Ephemeris Generation template to cluster
» Propagate and record state data every 30 days» Drag modeled using Jacchia-Roberts with Schatten Mean-Nominal solar flux predictions + ballistic coefficient
4. Build compare template (2200 obj. x 3 ESC ≈ 6600 tasks)» Each task is comparison of one object and one asset ephemeris
5. Submit conjunction comparison template» Compare each pair every 30 days for 5 days and find conjunctions within 50 km sphere
Process Description
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Jan-2008 Jan-2012 Jan-2016 Jan-2020 Jan-2024 Jan-2028800
810
820
830
840
850
860
870
880
890Fengyun-1C Debris - Height Evolution
Eq
uato
rial H
eig
ht (k
m)
Fengyun 1-C Debris Height Evolution
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2008 2010 2012 2014 2016 2018 2020 2022 2024 2026 20280
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20
30
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50
60
70
80
90
Year
Nu
mb
er
of
Un
iqu
e C
A E
ven
tsClose Approach Predictions: Fengyun-1C Debris vs. EOS
AquaAuraTerraEOS - Total
Future Close Approach Rates
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Detailed Results
► HPC solution made this analysis possible
» Reduced computation time from weeks to days
► Very little change in mean SMA of Fengyun-1C debris population over 20 years 20-30 meters
► Conjunction Events recorded in 2008 = 23
► Conjunction Events recorded in 2027 = 64
» Nearly triple the current rate in 20 years
► After 20 years, 85% of remaining Fengyun-1C debris still above ESC altitude and yet to fully impact constellation
» 7% reduction from 2008 value
16
Future Work
► Longer Propagation Times
» 20 years only tells part of the story
» How long until majority re-enters?
» How bad will it get?
► Improvements to HPC Environment
» Windows HPC 2008
» More automation possible
» How will it scale to many more compute nodes?
► Apply this technique to other orbital regimes and assets
» NPOESS and NPP
» Geosynchronous orbit regime
» Magnetospheric MultiScale Mission (MMS)