CSSI www.centerforspace.com

Satellite Orbital Conjunction Reports Assessing Threatening Encounters in

Space (SOCRATES) Dr. T.S. Kelso and Dr. Sal Alfano

Center for Space Standards and Innovation

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Overview

• Introduction

• Background

• Methodology

• Demonstration

• Conclusions

• Epilog

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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• 2,658 payloads vs. 8,478 objects (as of 2005 Jan 13)• Limited to public access TLEs (no active DOD satellites)

– Full catalog would be 2,927 payloads vs. 9,231 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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Epilog

• Impact of US Public Law 108-136:– Restricts transfer of data or “analysis of tracking data”

without SECDEF approval– Currently no stated policy clarifying restrictions

• CSSI believes:– Restriction applies only to analysis revealing accuracy

and limitations of SSN sensors– SOCRATES reports are okay, although TLE data will

have to be obtained via user’s Space Track account