CLOSE APPROACH PREDICTION ANALYSIS OF THE EARTH SCIENCE CONSTELLATION WITH THE FENGYUN-1C DEBRIS Matthew Duncan - a.i. solutions, Inc. Colorado Springs, CO David Rand - a.i. solutions, Inc. Lanham, MD Goddard Space Flight Center Mission Operations and Mission Services/ Flight Dynamics Analysis Branch 14th Annual Improving Space Operations Workshop Suitland, Maryland April , 2008

2 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

Cataloged objects >10 cm diameter Images courtesy NASA Orbital Debris Program Office Recent Debris Population

4 March Tracked objects >10 cm diameter (FENGYUN-1C Debris in red) Images courtesy NASA Orbital Debris Program Office Current Debris Population

5 The collision risk due to orbital debris is increasing: » ~14,000 tracked objects >1 cm 2 » 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 EOS Orbit

6 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

7 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 all ESC missions had at least one conjunctionevent 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 ofcritical importance

8 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 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

9 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

10 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

11 HeadNodeCN01CN02CN03CN04CN05 Gigabit Switch Corp. Network Monitor, Keyboard, Mouse on HeadNode HPC Cluster Typical Configuration

12 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

13 Fengyun 1-C Debris Height Evolution

14 Future Close Approach Rates

15 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 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)