CLOSE APPROACH PREDICTION ANALYSIS OF THE EARTH SCIENCE CONSTELLATION WITH THE FENGYUN-1C DEBRIS Matthew Duncan - a.i. solutions, Inc. Colorado Springs,

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

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Mean Equatorial Height(km)

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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

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890Fengyun-1C Debris - Height Evolution

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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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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

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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)