4.3 Debris cataloging and database management

Space debris tracking is crucial for maintaining safe space operations. Cataloging and database management form the backbone of this effort, allowing us to keep tabs on countless objects orbiting Earth.

These systems help identify potential collisions and inform mitigation strategies. By fusing data from multiple sources and constantly updating databases, we can better understand and predict the evolving space debris environment.

Space Object Cataloging

Space Object Catalog and Orbital Elements

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• Space object catalogs maintain a comprehensive database of all known objects in Earth orbit including active satellites, defunct satellites, rocket bodies, and debris fragments
• Catalogs assign each object a unique identifier and track its orbital parameters over time to predict its future position and velocity
• Orbital elements describe an object's orbit around Earth and include parameters such as semi-major axis, eccentricity, inclination, right ascension of the ascending node, argument of perigee, and mean anomaly
• These elements enable the calculation of an object's position and velocity at any given time using mathematical models of orbital motion (Kepler's laws)

Two-Line Element Sets (TLEs)

• TLEs are a standardized format for sharing orbital data consisting of two 69-character lines of text
• The first line includes the object's identifier, classification, launch year, launch number, piece tag, epoch year, epoch day, first time derivative of the mean motion, second time derivative of the mean motion, and drag term
• The second line contains the object's inclination, right ascension of the ascending node, eccentricity, argument of perigee, mean anomaly, and mean motion
• TLEs are generated from observations by the U.S. Space Surveillance Network and distributed publicly through the Space-Track website for most unclassified objects

Space-Track Website and Data Access

• Space-Track is a U.S. government website operated by the U.S. Space Force that serves as the primary public platform for sharing space object tracking data
• Registered users can access a database of current and historical TLEs, perform limited queries and analysis, and download data in various formats
• Space-Track also provides notifications and analysis of close approaches (conjunctions) between space objects
• Access to certain data and capabilities on Space-Track is restricted based on user affiliation (U.S. government, commercial, academic, etc.) and level of authorization

Conjunction Analysis and Data Fusion

Conjunction Assessment and Collision Avoidance

• Conjunction analysis involves screening space objects against each other to predict close approaches and assess collision risk
• Satellite operators perform conjunction analysis using TLEs and higher-fidelity ephemerides to identify conjunctions with their spacecraft days to weeks in advance
• If a conjunction poses a high collision risk, operators can plan and execute collision avoidance maneuvers to reduce the probability of a collision
• Some conjunction assessment services (NASA CARA) provide additional analysis and recommendations to help operators decide whether a maneuver is necessary

Data Fusion for Improved Space Situational Awareness

• Data fusion techniques combine tracking data from multiple sources to improve the accuracy and completeness of the space object catalog
• Fused data sources can include government, commercial, and international radar and optical observations, satellite-based observations, and operator-provided ephemerides
• By combining data from sensors with different characteristics (wavelength, geographic location, sensitivity), data fusion can help detect and track small debris, resolve closely-spaced objects, and reduce uncertainty in orbital predictions
• Advanced data fusion algorithms (multi-hypothesis testing) can also help identify maneuvers, breakups, new launches, and other changes in the space environment

Database Updates and Maintenance

• As new tracking observations are collected, space object databases must be continuously updated to reflect the latest information on each object's orbit
• Database updates may involve adding new objects, removing decayed objects, refining orbital elements based on new observations, and incorporating operator-provided data
• Maintaining an accurate and up-to-date database is critical for conjunction assessment and other space situational awareness applications
• Database maintenance also involves periodic calibration of tracking sensors, upgrades to processing software, and quality control checks to identify and resolve anomalies

Debris Population Modeling and Forecasting

• Space debris population models use statistical methods to estimate the current and future distribution of debris in Earth orbit based on historical data and projections of future launches and breakups
• NASA's Orbital Debris Engineering Model (ORDEM) and ESA's Meteoroid and Space Debris Terrestrial Environment Reference (MASTER) are widely used debris population models
• These models enable analysis of debris collision risk, evaluation of debris mitigation measures, and planning for debris removal missions
• Debris population forecasts inform national and international policy decisions on space traffic management and long-term sustainability of space activities

Data Management and Sharing

Historical Data Archiving and Analysis

• Effective space situational awareness requires the ability to access and analyze historical data on space objects and the space environment
• Space surveillance organizations maintain archives of tracking observations, orbital elements, conjunction assessments, and other data products
• These archives enable trend analysis, anomaly investigation, model validation, and research into the long-term evolution of the space debris environment
• Challenges in historical data management include ensuring data quality, consistency, and accessibility across different systems and formats

International Data Sharing and Collaboration

• Sharing space situational awareness data among nations and organizations is essential for ensuring the safety and sustainability of space activities
• The U.S. shares tracking data and conjunction warnings with satellite operators worldwide through the Space-Track website and other channels
• Other nations with space surveillance capabilities (Russia, China, EU) also share data to varying degrees through bilateral and multilateral agreements
• International organizations (IADC, UNCOPUOS) provide forums for coordination and development of guidelines for space situational awareness data sharing
• Challenges in international data sharing include data security, proprietary information, and political sensitivities around military and intelligence assets