improved conjunction analysis via collaborative ssa
DESCRIPTION
Improved Conjunction Analysis via Collaborative SSA. T.S. Kelso, D. Vallado (CSSI) J. Chan, B. Buckwalter (Intelsat). Overview. Motivation Background Proposed Solution Validation SOCRATES-GEO Future Enhancements Summary & Conclusions. Motivation. - PowerPoint PPT PresentationTRANSCRIPT
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Improved Conjunction Analysis via Collaborative SSA
T.S. Kelso, D. Vallado (CSSI)J. Chan, B. Buckwalter (Intelsat)
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Fifth European Conference on Space Debris, 2009 Mar 30-Apr 2Pg 2 of 26
Overview
• Motivation
• Background
• Proposed Solution
• Validation
• SOCRATES-GEO
• Future Enhancements
• Summary & Conclusions
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Fifth European Conference on Space Debris, 2009 Mar 30-Apr 2Pg 3 of 26
Motivation
• Recent events emphasize need for improved SSA for conjunction analysis– Chinese ASAT test (2007 Jan 11)
• 2,529 pieces cataloged to date (only 49 decayed)
– USA 193 intercept (2008 Feb 21)• 174 pieces cataloged (1 still on orbit)
– ISS maneuver to avoid Cosmos 2421 debris (2008 Aug)• 509 pieces cataloged (48 still on orbit)
– Iridium 33/Cosmos 2251 collision (2009 Feb 10)• 999 pieces cataloged to date (822 public); only 6 decayed
– ISS evacuation (2009 Mar 12), move (2009 Mar 22)
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SATCAT Growth: 1957 to Present
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Motivation at GEO
• Geostationary orbit (GEO) is a limited resource– More satellites = more conjunctions
• 30 payloads launched in 2008• >369 active payloads
– Implications of a collision are significant• Potential loss of colliding satellites and associated revenues• Increase in debris, putting other satellites at risk
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Background
• Conjunction analysis needs full-catalog orbital data– TLEs are currently the only such source
• Low accuracy results in high false-alarm rate
• Current system limited to non-cooperative tracking– US SSN uses combination of radar and optical resources
• Operational satellites most difficult to track due to maneuvers– Maneuvers typically not known ahead of time
– Delays in detecting maneuvers can result in poor accuracy or even ‘lost’ satellites
– Requires more SSA resources to maintain orbits
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Proposed Solution
• Satellite operators already maintain orbits– Active ranging, GPS can be very accurate
• Develop Data Center to collect operator data– Use operator data to improve conjunction analysis– Provide analysis/data to all contributors
• Current Data Center participation (133+35)– Intelsat (55+6), Inmarsat (11), EchoStar (6), SES (41+1:
Astra, New Skies, Americom), NOAA (4), Star One (6), Telesat (6+18), EUMETSAT (4)
• Pending: IAI (3), Paradigm (7)
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Analysis of Orbital Data Sources
• Many sources of operator orbital data– Direct from satellite operator (Data Center)– Public sources
• GPS (almanacs, precise ephemerides)• GLONASS (precise ephemerides)• Intelsat (11-parameter data, ephemerides)• NOAA, EUMETSAT (state vectors)
• Challenges– User-defined data formats– Variety of coordinate frames & time systems used
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Supplemental TLEs
• Uses public orbital data– GPS almanacs– GLONASS precise ephemerides– Intelsat 11-parameter data
• Import data into STK to generate ephemerides
• Generate TLE from ephemerides– Allows users to see benefit
• Test cases with supporting data
– Overcomes limitations in most orbital software that can only handle TLEs/SGP4
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GPS Almanacs vs. TLEs
Mean: 1.292 km
Max: 3.073 km
Mean: 7.544 km
Max: 32.449 km
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GPS Supplemental TLEs
Mean: 0.872 km
Max: 2.366 km
Mean: 7.544 km
Max: 32.449 km
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GLONASS Supplemental TLEs
Mean: 3.301 km
Max: 9.388 km
Mean: 0.201 km
Max: 0.539 km
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Case Study: Intelsat Data Comparisons
IS-6B IS-3R IS-11
IS-6B IS-3RIS-11
Owner ephemeridesAFSPC TLEs
43.25° W 43.00° W 42.75° W
Spacing = 184 km
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Case Study: ASTRA 1 Cluster
• Open source image of cluster– http://www.foton.co.za/assa_imaging.htm
• Taken 2009 Jan 21 at 20:21:11 UTC
• Site location: 33.94058 S, 18.51294 E, 10 m– Pinelands, a suburb of Cape Town, South Africa
• Telescope: 6-inch, f/2.7 reflector
• FOV: 54.7 x 40.2 arcminutes
• Compared SES ephemerides and latest TLEs
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SES EphemeridesHipparcos StarsAFSPC TLEs
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SES EphemeridesHipparcos StarsAFSPC TLEs
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SES EphemeridesHipparcos StarsAFSPC TLEs
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1H to _1H = 71 km
SES EphemeridesHipparcos StarsAFSPC TLEs
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SES EphemeridesHipparcos StarsAFSPC TLEs
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SOCRATES-GEO
• Extension of SOCRATES– Satellite Orbital Conjunction Reports Assessing
Threatening Encounters in Space– Running since 2004 May
• Looks for any time anything gets within 5 km of payload– 2,959 payloads vs. 12,817 total objects (as of 2009 Mar 31)– 13,979 conjunctions (2009 Mar 31 + 7 days)
• Runs automatically twice per day• Generates standard reports available via the Internet• Uses only TLEs
– Limited accuracy due to non-cooperative tracking– Does not account for maneuvers well– US SSN tracks over 19,000 objects
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SOCRATES-GEO Today
• Includes all objects which pass ±250 km of GEO– 752 payloads vs. 1,334 total objects (as of 2009 Mar 31)– 1,094 conjunctions within 50 km (2009 Mar 31 + 7 days)
• Uses best data sources available
• Generates standard reports– Runs in under 15 minutes on standard PC– Provides links to standard (OEM) orbital data
• Allows user-defined notification criteria
• Automatically sends notification
• Web access to latest data via secure system
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Data sources
Owner ephemeris
Public orbital data
TLE data
Convert to standard format
Generate ephemerides
Produce enhanced TLEs
Select GEO data
Data preparation
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Future Enhancements
• Process new data as received– User defines notification interval– Parallel analysis tool for maneuver planning
• Improved data status page– Data type, age, and quality– Direct contact information for operational satellites
• Enhanced graphs, reports, visualization– Customizable tool kits
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Summary & Conclusions
• Bottom line:– Technical solution is easy
• Biggest obstacle:– Data sharing policies
• Other issues:– Organization– Resources & Funding
• Together we can work today to mitigate risk
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Questions?