How to Track Real-Time Satellite Positions: A Complete Guide

There are over 10,000 active satellites orbiting Earth right now, along with tens of thousands of pieces of tracked debris. Whether you are a satellite operator managing a constellation, a defense analyst monitoring adversary assets, an educator teaching orbital mechanics, or simply someone who wants to know when the ISS will fly overhead, understanding how satellite tracking works is increasingly relevant.

This guide explains the fundamentals of satellite tracking: what the data looks like, how positions are calculated, what the different orbit types mean, and how you can track satellites in real time using the SpaceNexus Satellite Tracker.

How Satellite Tracking Works

Satellite tracking begins with observation. The U.S. Space Force's 18th Space Defense Squadron operates a global network of radars, telescopes, and sensors that detect and track objects in Earth orbit. This network, the Space Surveillance Network (SSN), tracks approximately 47,000 objects, including active satellites, spent rocket bodies, and debris fragments larger than about 10 cm.

When sensors detect an object, they measure its position and velocity at a specific time. These measurements are processed into standardized orbital element sets that describe the object's orbit mathematically. The most widely used format for distributing this data is the Two-Line Element set, or TLE.

Understanding TLE Data

A TLE (Two-Line Element set) is a compact, standardized format that encodes enough information to predict a satellite's position for several days into the future. Despite its age (the format was developed in the 1960s), it remains the de facto standard for sharing orbital data.

A TLE consists of two 69-character lines preceded by an optional title line. The elements encoded include:

• Catalog number: A unique identifier for each tracked object (e.g., 25544 for the ISS)
• Epoch: The reference time for the element set, the moment at which the orbital elements are most accurate
• Inclination: The angle between the orbital plane and the equatorial plane (0 degrees = equatorial, 90 degrees = polar)
• Right Ascension of Ascending Node (RAAN): The orientation of the orbital plane relative to a fixed reference in space
• Eccentricity: How elliptical the orbit is (0 = circular, approaching 1 = highly elliptical)
• Argument of Perigee: The orientation of the orbit's lowest point within the orbital plane
• Mean Anomaly: The satellite's position along its orbit at the epoch time
• Mean Motion: How many orbits the satellite completes per day (a satellite in 90-minute LEO orbit completes about 16 per day)
• Drag term (B*): A coefficient that models atmospheric drag effects on the orbit

TLE data is freely available from CelesTrak (celestrak.org), operated by Dr. T.S. Kelso, which redistributes TLE data from Space-Track.org (the official U.S. government source) in more accessible formats. SpaceNexus sources its orbital data from CelesTrak and updates positions continuously.

SGP4: Predicting Satellite Positions

TLE data alone tells you where a satellite was at the epoch time. To calculate where it is right now, or where it will be in the future, you need a propagation algorithm that models how the orbit evolves over time.

The standard algorithm for TLE-based prediction is SGP4 (Simplified General Perturbation model 4), developed by the U.S. Air Force. SGP4 accounts for several forces that perturb a satellite's orbit:

• Earth's oblateness (J2): Earth is not a perfect sphere; it bulges at the equator. This is the dominant perturbation for most orbits, causing the orbital plane to precess (rotate) over time.
• Atmospheric drag: For LEO satellites (below ~1000 km), atmospheric drag gradually lowers the orbit and eventually causes reentry. The drag term (B*) in the TLE models this effect.
• Solar and lunar gravity: The gravitational pull of the Sun and Moon perturbs orbits, particularly at higher altitudes.
• Solar radiation pressure: Photons from the Sun exert a small but measurable force on satellites, especially those with large solar panels or thin structures.

SGP4 is accurate to approximately 1 km for predictions a few days after the TLE epoch, degrading to tens of kilometers after a week or more. This is sufficient for most tracking applications but not for precision tasks like collision avoidance, which require higher-fidelity propagation.

Orbit Types Explained

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

LEO is the most populated orbital regime, home to the majority of active satellites. Key characteristics:

• Orbital period: 88-127 minutes (approximately 16 orbits per day at 400 km)
• Latency: 1-4 milliseconds (making LEO ideal for broadband internet)
• Notable occupants: International Space Station (ISS, 420 km), Starlink (550 km), Planet Labs (500 km), Hubble Space Telescope (540 km)
• Considerations: Atmospheric drag is significant below ~600 km, requiring periodic reboost. LEO satellites have limited ground coverage per pass, which is why constellations require hundreds or thousands of satellites.

Explore LEO satellites on the SpaceNexus Satellite database, which catalogs operator, mission, orbit parameters, and status for thousands of objects.

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

MEO is primarily used by navigation constellations:

• Orbital period: 2-24 hours
• Notable occupants: GPS (~20,200 km, 31 operational satellites), Galileo (~23,222 km), GLONASS (~19,100 km), BeiDou MEO satellites
• Considerations: MEO requires passage through the Van Allen radiation belts, necessitating radiation-hardened electronics. The higher altitude provides larger ground coverage per satellite.

Geostationary Orbit (GEO): 35,786 km Altitude

At exactly 35,786 km altitude with zero inclination, a satellite's orbital period matches Earth's rotation; it appears stationary relative to the ground. This makes GEO invaluable for specific applications:

• Communications: GEO satellites can provide continuous coverage of a fixed region. Three satellites can cover nearly the entire globe (excluding polar regions). Companies like SES, Intelsat, and Viasat operate large GEO fleets.
• Weather monitoring: GOES (U.S.), Meteosat (Europe), and Himawari (Japan) provide continuous weather imagery from GEO.
• Early warning: Military early warning satellites in GEO detect missile launches using infrared sensors.
• Orbital slot allocation: GEO orbital positions are allocated by the ITU and are extremely valuable. Explore allocation data in the SpaceNexus Orbital Slots module.

Other Notable Orbits

• Sun-Synchronous Orbit (SSO): A polar LEO orbit where the orbital plane precesses to maintain a constant angle with the Sun. This ensures consistent lighting conditions for Earth observation. Most EO satellites use SSO.
• Molniya Orbit: A highly elliptical 12-hour orbit with high apogee over the Northern Hemisphere, used by Russia for communications coverage of high-latitude regions.
• Cislunar Orbits: Orbits extending to the Moon and Lagrange points, increasingly relevant as Artemis and commercial lunar programs expand.

Tracking Specific Satellites

International Space Station (ISS)

The ISS is the brightest artificial object in the night sky and one of the most tracked. Orbiting at approximately 420 km altitude with a 51.6-degree inclination, it completes an orbit every 92 minutes. The ISS is visible to the naked eye during passes over your location; it appears as a bright, steadily moving point of light.

Starlink Constellation

SpaceX's Starlink constellation is the largest satellite constellation ever deployed, with over 7,000 operational satellites in LEO at approximately 550 km altitude. Starlink satellites are sometimes visible as "trains" shortly after launch before they raise their orbits and spread out. Track the full constellation using the SpaceNexus Constellation Monitor.

GPS Constellation

The GPS constellation consists of 31 operational satellites in six orbital planes at approximately 20,200 km altitude. Each satellite completes two orbits per day. GPS is a MEO constellation, much higher than Starlink but much lower than GEO communications satellites.

Track Satellites with SpaceNexus

The SpaceNexus Satellite Tracker visualizes 19,000+ tracked objects on an interactive 3D globe with real-time positions calculated from the latest CelesTrak TLE data using SGP4 propagation. Filter satellites by orbit type, operator, constellation, or mission type. Click any satellite to see its orbital parameters, ground track, and operator information.

Beyond tracking, SpaceNexus integrates satellite data with our broader intelligence platform. See which companies operate which satellites through Company Profiles. Monitor constellation deployment progress. Track orbital slot utilization in Orbital Slots. And monitor the space environment (debris density, collision risk, and reentry predictions) in our Space Environment module.

Start tracking satellites for free with SpaceNexus.