System Architecture
A breakdown of the computational engines, astrodynamics algorithms, and data pipelines that power our Conjunction Assessment (CA) and Space Situational Awareness (SSA) capabilities.
Orbital Propagation Layer
SGP4/SDP4 Implementation
Our baseline propagator utilizes the Simplified General Perturbations-4 (SGP4) algorithm for specialized calculation of satellite state vectors from Two-Line Elements (TLEs). For deep-space objects (period > 225 minutes), the system automatically switches to SDP4 (Deep Space), accounting for lunar-solar gravitational resonance and earth tesseral harmonics. This ensures compliance with established USSPACECOM standards for TLE propagation.
High-Fidelity Force Models (Orekit)
For precision conjunction screening, we employ a Java-Python bridge to the Orekit astrodynamics library. This allows for numerical propagation incorporating:
- EGM96 Earth Gravity Field (up to 70x70 degree/order)
- NRLMSISE-00 Atmospheric Drag Modeling
- Third-body gravity (Sun & Moon)
- Solar Radiation Pressure (SRP) with spherical spacecraft modeling
Conjunction Assessment (CA)
Screening Volume & Filters
We utilize a pre-filter stage ("All-vs-All") based on apogee/perigee filters to eliminate geometrically impossible collision pairs. Candidate pairs then undergo a Smart Sieve process using a 3D Euclidean distance check promoted over the entire screening interval (typically 7 days), reducing computational load by 98% compared to brute-force methods.
Probability of Collision ($P_c$)
For objects violating the miss distance threshold, $P_c$ is calculated using the Foster-1992 method. This involves projecting the covariance ellipsoids of both the primary and secondary object into the 2D conjunction plane (B-plane) at the Time of Closest Approach (TCA).
Data Ingestion & Provenance
Ingestion
Direct API integration with Space-Track.org. Automated cron jobs fetch incremental TLE updates every 6 hours. Data is parsed, identifying catalog ID changes and launch pieces.
Validation
Incoming state vectors undergo consistency checks (e.g., eccentricity < 1 for LEO). Anomalous decay rates or mean motion derivatives are flagged for human analyst review.
Storage
PostgreSQL with PostGIS extension for spatial indexing. Ephemerides are stored as BLOBs with full audit trails (timestamp, source, original TLE line).
Security & Compliance
The system implements a strict Role-Based Access Control (RBAC) model. Route protection is enforced via JWT (JSON Web Tokens) with short-lived expiration. All backend traffic is encrypted via TLS 1.3. Conjunction Data Messages (CDMs) are generated in CCSDS compliant XML format, ensuring interoperability with major catalog providers.
System Specification Document v2.4 • INTERNAL USE ONLY