Satellite Tracking Explained: How It Works and Why It Matters

There are over 19,000 trackable objects orbiting Earth right now: active satellites, spent rocket bodies, and debris fragments. Tracking these objects is critical for collision avoidance, communications, scientific research, and national security. Here's how it all works.

What Is Satellite Tracking?

Satellite tracking is the process of determining and predicting the position and velocity of objects in Earth orbit. It combines ground-based observations (radar, optical telescopes, laser ranging) with mathematical models of orbital mechanics to maintain a catalog of every known space object.

Who Tracks Satellites?

• U.S. Space Force (18th Space Defense Squadron): Maintains the authoritative public catalog of tens of thousands of tracked objects using the Space Surveillance Network (SSN), a global network of radar and optical sensors
• CelesTrak: Dr. T.S. Kelso's service that distributes orbital data from Space-Track.org in accessible formats
• LeoLabs: Commercial tracking service using phased-array radar, specializing in LEO debris
• ExoAnalytic Solutions: Commercial optical tracking network for GEO and deep space
• EU Space Surveillance and Tracking (EU SST): European tracking network

Understanding TLE Data

Two-Line Element sets (TLEs) are the standard format for describing a satellite's orbit. Published by the U.S. Space Force and distributed by CelesTrak and Space-Track.org, each TLE contains (newer objects with six-digit catalog numbers are published in the equivalent OMM format instead):

• Epoch: The reference time for the orbital elements
• Inclination: Angle of the orbit relative to the equator
• RAAN: Right Ascension of Ascending Node, where the orbit crosses the equator
• Eccentricity: How elliptical the orbit is (0 = circle, <1 = ellipse)
• Argument of perigee: Orientation of the ellipse within the orbital plane
• Mean anomaly: Position of the satellite along its orbit at epoch
• Mean motion: Number of orbits per day

Using these six orbital elements plus drag coefficients, propagation algorithms (like SGP4) can predict a satellite's position days or weeks into the future.

Orbit Types

Low Earth Orbit (LEO): 200-2,000 km

Home to the ISS, Starlink, and most Earth observation satellites. Orbital period: 90-120 minutes. LEO is the most crowded orbital regime and where most collision risks exist.

Medium Earth Orbit (MEO): 2,000-35,786 km

Used by GPS, Galileo, and other navigation constellations. Orbital period: 2-24 hours.

Geostationary Orbit (GEO): 35,786 km

Satellites appear stationary relative to the ground, making GEO ideal for communications and weather monitoring. The GEO belt is limited: orbital slots are allocated by the ITU and are valuable real estate.

Highly Elliptical Orbits (HEO)

Used for specialized applications like Molniya orbits (coverage of polar regions) and Tundra orbits.

Collision Avoidance

With thousands of active satellites and millions of debris fragments, collision avoidance is increasingly critical:

• The 18th SDS issues Conjunction Data Messages (CDMs) when two objects are predicted to pass within a threshold distance
• Satellite operators perform collision avoidance maneuvers (CAMs) when the probability of collision exceeds a threshold (typically 1 in 10,000)
• The Kessler syndrome, a cascading chain of collisions generating ever more debris, is a long-term concern, particularly in congested LEO bands
• SpaceX's Starlink satellites perform autonomous avoidance maneuvers using onboard propulsion

The Space Debris Challenge

There are approximately:

• 36,500 tracked objects larger than 10 cm
• 1,000,000+ objects between 1-10 cm (too small to track reliably)
• 130,000,000+ objects smaller than 1 cm

Even a 1 cm paint fleck at orbital velocity (7.8 km/s in LEO) carries the kinetic energy of a hand grenade. Active debris removal (ADR) efforts by companies like Astroscale, ClearSpace, and TransAstra are beginning to address this challenge.

Track Satellites with SpaceNexus

SpaceNexus's Satellite Tracker shows satellites on an interactive globe, with positions computed from CelesTrak orbital data (in OMM format, so objects with six-digit catalog numbers are included). Filter by orbit type, operator, or constellation. Our Space Environment module monitors debris density and collision risk.

Start tracking satellites for free.