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). 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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Improved conjunction analysis via collaborative ssa

Improved Conjunction Analysis via Collaborative SSA

T.S. Kelso, D. Vallado (CSSI)J. Chan, B. Buckwalter (Intelsat)


Overview

Overview

  • Motivation

  • Background

  • Proposed Solution

  • Validation

  • SOCRATES-GEO

  • Future Enhancements

  • Summary & Conclusions


Motivation

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)


Satcat growth 1957 to present

SATCAT Growth: 1957 to Present


Motivation at geo

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


Background

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


Proposed solution

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)


Analysis of orbital data sources

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


Supplemental tles

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


Gps almanacs vs tles

GPS Almanacs vs. TLEs

Mean: 7.544 km

Max: 32.449 km

Mean: 1.292 km

Max: 3.073 km


Gps supplemental tles

GPS Supplemental TLEs

Mean: 7.544 km

Max: 32.449 km

Mean: 0.872 km

Max: 2.366 km


Glonass supplemental tles

GLONASS Supplemental TLEs

Mean: 0.201 km

Max: 0.539 km

Mean: 3.301 km

Max: 9.388 km


Case study intelsat data comparisons

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


Case study astra 1 cluster

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


Improved conjunction analysis via collaborative ssa

SES EphemeridesHipparcos StarsAFSPC TLEs


Improved conjunction analysis via collaborative ssa

SES EphemeridesHipparcos StarsAFSPC TLEs


Improved conjunction analysis via collaborative ssa

SES EphemeridesHipparcos StarsAFSPC TLEs


Improved conjunction analysis via collaborative ssa

SES EphemeridesHipparcos StarsAFSPC TLEs

1H to _1H = 71 km


Improved conjunction analysis via collaborative ssa

SES EphemeridesHipparcos StarsAFSPC TLEs


Socrates geo

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


Socrates geo today

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


Improved conjunction analysis via collaborative ssa

Data preparation

Data sources

Owner ephemeris

Convert to standard format

Select GEO data

Public orbital data

Generate ephemerides

TLE data

Produce enhanced TLEs


Future enhancements

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


Summary conclusions

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


Questions

Questions?


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