Satellite Orbital Conjunction Reports
Assessing Threatening Encounters in
Space (SOCRATES)
Dr. T.S. Kelso and Dr. Sal Alfano
Center for Space Standards and Innovation
CSSI
www.centerforspace.com
Overview
• Introduction
• Background
• Methodology
• Demonstration
• Conclusions
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Introduction
• Many operators are aware of the possibility of a
collision between their satellite and another object
• Few are aware of the frequency of occurrences
• No central source of conjunction information
• Problem is further confounded by lack of
– Timely, comprehensive orbital data (including
covariance)
– Standard software
– Computationally efficient algorithms
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Introduction
• Result
– Hundreds of conjunctions within 1 km go unreported
each week
– Billions of dollars of space hardware—and their
associated missions—are put at risk
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Background
• Center for Space Standards & Innovation (CSSI)
offers SOCRATES conjunction advisory service
– Each day, CSSI runs all payloads (active and inactive)
against all objects on orbit
• 2,686 payloads vs. 8,593 objects (as of 2005 Aug 17)
• Limited to public access TLEs (no active DOD satellites)
– Full catalog would be 2,954 payloads vs. 9,379 objects
• Provides daily, searchable reports via CelesTrak
– Reports and associated data used to produce them are
freely available to the public
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Methodology
• CSSI uses:
– Standard data sources: NORAD two-line element sets
– Standard orbital models: NORAD SGP4/SDP4
– COTS software: Satellite Tool Kit with STK/CAT
(Conjunction Analysis Tools)
• CSSI produces daily STK/CAT runs reporting:
– Minimum distance at time of closest approach (TCA)
– Maximum probability of collision
– Coming: First-order estimate of true probability of
collision
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Methodology
• Capability now exists to build full STK scenarios
on the fly directly from SOCRATES reports
– Provides quick, easy way to incorporate all aspects of a
particular conjunction into a 3-D framework for additional
analysis
• Allows user to easily incorporate higher quality data, if available
• Flows directly into other space operations analysis, such as
maneuver planning
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Demonstration
• Easy to find from CelesTrak home page
– Click on link for SOCRATES
– Provides basic information along with:
• Top 10 Conjunctions by Maximum Probability
• Top 10 Conjunctions by Minimum Range
• Search Capability
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Demonstration
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Demonstration
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Demonstration
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Demonstration
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Demonstration
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Conclusions
• SOCRATES provides regular reports of satellite
conjunctions using:
– Standard, timely data (TLEs)
– Standard orbital models (SGP4)
– Extensible COTS software (STK)
• Reports are freely available
• Provides full-catalog SSA
• Easy to use, computationally efficient
• Raises awareness about this important space control issue
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