CelesTrak API
CelesTrak provides free Two-Line Element (TLE) orbital data for all tracked Earth-orbiting objects sourced from US Space Command, enabling satellite tracking and pass prediction.
Score Breakdown
⚙ Agent Friendliness
🔒 Security
HTTPS available but site also serves HTTP. No auth means no secret management needed — a simplicity advantage. No sensitive data; TLE data is public domain. No formal security posture documented.
⚡ Reliability
Best When
An agent needs free, public orbital element data for satellite tracking, pass prediction, or orbital mechanics calculations without authentication overhead.
Avoid When
You need sub-meter precision ephemeris, real-time sensor data, or data for classified satellites.
Use Cases
- • Satellite pass prediction for ground stations
- • Space situational awareness and conjunction analysis
- • Amateur radio satellite tracking (AOS/LOS calculation)
- • Orbital mechanics research and education
- • Space debris monitoring and avoidance planning
Not For
- • Real-time telemetry or satellite control
- • High-precision ephemeris (GPS-level accuracy)
- • Commercial imagery ordering or tasking
- • Classified or military orbital data
Interface
Authentication
No authentication required for most data. GP data catalog uses no auth. Some supplemental data formats require free account registration.
Pricing
Operated by Dr. T.S. Kelso, funded by volunteers. Donation encouraged but not required. Service has operated since 1985 with no monetization.
Agent Metadata
Known Gotchas
- ⚠ No formal rate limit documentation — aggressive polling may result in IP blocks without warning
- ⚠ TLE data format is fixed-width ASCII — agents must use a TLE parser library (sgp4 or skyfield), not naive string parsing
- ⚠ Data freshness varies by object class — TLEs can be hours to days old; check epoch before use
- ⚠ No SLA or uptime guarantee — volunteer-operated service may have unannounced outages
- ⚠ API endpoints and data formats have changed over the years with minimal versioning notice
- ⚠ SOCRATES conjunction data is batch-processed, not real-time
Alternatives
Full Evaluation Report
Detailed scoring breakdown, competitive positioning, security analysis, and improvement recommendations for CelesTrak API.
Scores are editorial opinions as of 2026-03-06.