Improved Conjunction Analysis via Collaborative SSA

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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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Overview

• Motivation
• Background
• Proposed Solution
• Validation
• SOCRATES-GEO
• Future Enhancements
• Summary Conclusions

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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
• gt369 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 (13335)
• Intelsat (556), Inmarsat (11), EchoStar (6), SES
  (411 Astra, New Skies, Americom), NOAA (4),
  Star One (6), Telesat (618), 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 0.201 km Max 0.539 km
Mean 3.301 km Max 9.388 km
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Case Study Intelsat Data Comparisons
Owner ephemeridesAFSPC TLEs
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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 202111 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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SES EphemeridesHipparcos StarsAFSPC TLEs
1H to _1H 71 km
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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
Data preparation
Owner ephemeris
Convert to standard format
Public orbital data
Generate ephemerides
Select GEO data
TLE data
Produce enhanced TLEs
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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?