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Improved Conjunction Analysis via Collaborative SSA

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.

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Improved Conjunction Analysis via Collaborative SSA

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  1. Improved Conjunction Analysis via Collaborative SSA T.S. Kelso, D. Vallado (CSSI)J. Chan, B. Buckwalter (Intelsat)

  2. Overview • Motivation • Background • Proposed Solution • Validation • SOCRATES-GEO • Future Enhancements • Summary & Conclusions

  3. 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)

  4. SATCAT Growth: 1957 to Present

  5. 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

  6. 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

  7. 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)

  8. 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

  9. 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

  10. GPS Almanacs vs. TLEs Mean: 7.544 km Max: 32.449 km Mean: 1.292 km Max: 3.073 km

  11. GPS Supplemental TLEs Mean: 7.544 km Max: 32.449 km Mean: 0.872 km Max: 2.366 km

  12. GLONASS Supplemental TLEs Mean: 0.201 km Max: 0.539 km Mean: 3.301 km Max: 9.388 km

  13. IS-6B IS-11 IS-3R 43.00° W 43.25° W 42.75° W IS-6B IS-3R IS-11 Spacing = 184 km Case Study: Intelsat Data Comparisons Owner ephemeridesAFSPC TLEs

  14. 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

  15. SES EphemeridesHipparcos StarsAFSPC TLEs

  16. SES EphemeridesHipparcos StarsAFSPC TLEs

  17. SES EphemeridesHipparcos StarsAFSPC TLEs

  18. SES EphemeridesHipparcos StarsAFSPC TLEs 1H to _1H = 71 km

  19. SES EphemeridesHipparcos StarsAFSPC TLEs

  20. 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

  21. 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

  22. Data preparation Data sources Owner ephemeris Convert to standard format Select GEO data Public orbital data Generate ephemerides TLE data Produce enhanced TLEs

  23. 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

  24. 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

  25. Questions?

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