A Guide to Online Data Resources About Satellites

Navigating the Digital Cosmos

The night sky, once the domain of astronomers and philosophers, is now a bustling superhighway of technology. Tens of thousands of artificial objects orbit our planet, from the life-sustaining International Space Station (ISS) to tiny CubeSats, defunct rocket bodies, and hazardous fragments of space debris. This orbital population is not just a curiosity; it’s a complex, high-stakes environment that requires constant monitoring. For professionals, hobbyists, and the public alike, a surprisingly vast collection of online resources exists to track, identify, and understand every object cataloged in Earth’s orbit.

These resources provide detailed data on satellites that have been launched, are currently in orbit, and those that have deorbited, burning up in the atmosphere or returning to Earth. Accessing this information has become essential for everything from space traffic management and collision avoidance to academic research and even amateur satellite spotting. This article explores the landscape of these digital tools, from the primary government sources that gather the raw data to the user-friendly websites and specialized databases that make it accessible to everyone.

Why Track Satellites?

The need for comprehensive satellite data stems from the simple fact that Earth’s orbit is a finite resource, and it’s becoming incredibly crowded. The launch of Sputnik 1 in 1957 opened the space age, and in the decades since, thousands of rockets have carried tens of thousands of payloads into orbit. This trend has accelerated dramatically with the rise of commercial “megaconstellations” like SpaceX’s Starlink, which deploys satellites in large batches.

This congestion creates a significant problem: the risk of collision. When two satellites collide, they don’t just stop working; they obliterate each other, creating a cloud of thousands of new pieces of high-velocity debris. Each new piece of debris increases the probability of further collisions, a cascading effect known as the Kessler syndrome.

Tracking every object, both active and defunct, is the only way to manage this risk. Satellite operators need to know if their multi-billion dollar asset is on a collision course with a piece of a 1970s-era rocket body. Astronomers need to plan their observations around bright, reflective satellite “trains” that can streak across their images. Governments need to maintain situational awareness for national security. And for many, the simple act of knowing what is flying overhead is a powerful connection to the human endeavor in space.

This collective need for Space Domain Awareness (SDA), or Space Situational Awareness (SSA), has driven the development of a global network of sensors and the public-facing databases that share their findings.

What Data Can Be Found?

Before diving into the resources themselves, it’s helpful to understand the basic types of information they provide. When a satellite is tracked, it’s not just a single dot on a map. A rich set of data is collected to describe its identity, its orbit, its purpose, and its status.

• Identification: Every cataloged object is given unique identifiers. The two most common are the Satellite Catalog Number (also called the NORAD ID) and the COSPAR ID (or International Designator). A NORAD ID is a simple sequential number; the ISS, for example, is 25544. A COSPAR ID is more descriptive, indicating the launch year, the launch number of that year, and a letter for each piece of the launch (e.g., 1998-067A for the first component of the ISS, the Zarya module).
• Orbital Data (Orbital Elements): This is the core data that describes a satellite’s path. It includes several key parameters, often packaged in a format called a Two-Line Element Set (TLE). This data tells you the satellite’s altitude, its tilt relative to the equator, the shape of its orbit, and its exact position at a specific point in time.
• Launch Information: Databases record when and from where an object was launched, as well as the rocket (launch vehicle) that carried it to space.
• Physical Characteristics: Some specialized databases also track an object’s physical properties, such as its mass, size, and shape. This is particularly important for predicting how it will behave upon reentry.
• Mission and Operator Data: Beyond the physics, many resources catalog the “human” side of the satellite: Who owns it? Who operates it? What is its purpose (e.g., communications, Earth observation, military, navigation)?
• Status: This is the critical, time-sensitive data. Is the satellite active and operational? Is it defunct and tumbling? Is it predicted to deorbit and reenter the atmosphere soon?

This collection of information, from raw orbital elements to detailed mission descriptions, is distributed across a variety of powerful online resources, each with a different focus and level of detail.

The Foundational Source: The U.S. Space Surveillance Network

Nearly all public satellite data originates from one primary source: the United States Space Surveillance Network (SSN). This is not a single website but a global network of more than 30 ground-based radar and optical telescopes, supplemented by space-based sensors. This network is operated by the United States Space Command (USSPACECOM).

The SSN is the workhorse of global space tracking. Its powerful radars, like the “Space Fence” on Kwajalein Atoll, can detect objects as small as a marble in Low Earth Orbit (LEO). Its optical telescopes monitor the more distant Geostationary Orbit (GEO), where communications and weather satellites reside.

This network generates hundreds of thousands of observations per day, which are fed to the 18th Space Defense Squadron (18 SDS). The 18 SDS is the unit responsible for maintaining the official, authoritative catalog of all human-made objects in Earth orbit. They are the ones who detect new launches, identify the payloads, catalog new debris, and issue collision warnings to satellite operators around the world.

While the full, high-precision data catalog is used by the military and partner organizations, a vast and useful subset of this data is made available to the public, satellite operators, and academic researchers for free.

Space-Track.org

The single most important public-facing portal for this foundational data is Space-Track.org. Operated by the 18 SDS, this website is the official source for the public U.S. satellite catalog. It’s a free service, but it requires users to create an account and agree to a user agreement.

Once inside, Space-Track.org offers a staggering amount of data, though its interface is more functional than flashy. It’s built for researchers and operators, not casual browsers. Its primary offering is the master satellite catalog (SATCAT). For any object in the catalog, a user can find:

• Current TLEs: The most up-to-date Two-Line Element sets, which are the raw data needed to calculate an object’s position.
• Launch Information: The launch date, site, and launch vehicle.
• Decay and Reentry Data: For objects that have deorbited, Space-Track provides the official decay date. It also provides “TIP Messages” (Tracking and Impact Prediction) for upcoming reentries, giving a window of when and where an object is expected to come down.
• Box Score: A high-level summary of the orbital environment, showing the total number of objects on orbit, broken down by status (payload, rocket body, debris) and country of origin.

Space-Track.org is the “source of truth.” Nearly every other tracking website or app, from amateur hobbyist sites to professional visualization tools, pulls its raw orbital data from the TLEs published on Space-Track.org. While it’s not a visual tool – it won’t show you a 3D map of orbit – it is the official library from which all other services borrow.

Understanding the Language of Orbit

To make sense of the data found on Space-Track and other sites, it’s essential to understand the basic concepts they use to describe an orbit. The data is almost always presented in a standardized format that, while efficient, can be confusing at first.

The “Two-Line Element” (TLE) Explained

The Two-Line Element Set is the standard data format for sharing the orbital elements of a satellite. It’s a legacy format, dating back to the days of punch cards, but it remains the universal language for orbit prediction.

A TLE consists of three lines: a title line, followed by “Line 1” and “Line 2.”

• Title Line: This is the simple, human-readable name of the object, such as “ISS (ZARYA)”.
• Line 1: This line is packed with information. It includes the satellite’s NORAD ID (25544) and its COSPAR ID (98067A). It also contains the “Epoch,” which is a precise timestamp telling you the exact moment (year, day, and fraction of a day) when these orbital elements were valid. This is important because orbits are constantly changing.
• Line 2: This line describes the “shape” of the orbit. It contains the numbers for inclination, eccentricity, apogee, perigee, and the satellite’s position within that orbit.

Software can read this block of text and numbers to calculate a satellite’s position, velocity, and path at any point in the recent past or near future. For a non-technical user, it’s not necessary to know how to read every number. It’s only important to know that the TLE is the “data packet” that powers all tracking applications.

Key Orbital Parameters

When you use a more user-friendly website, it will translate the TLE’s numbers into plain English. The most common terms you’ll see are:

• Inclination: This is the tilt of the satellite’s orbit relative to the Earth’s equator, measured in degrees. An inclination of 0 degrees means it orbits directly above the equator. The ISS has an inclination of 51.6 degrees, meaning it travels between 51.6° North and 51.6° South latitude. A satellite in a polar orbit has an inclination near 90 degrees, allowing it to pass over the entire planet as the Earth rotates beneath it.
• Apogee and Perigee: Satellites don’t orbit in perfect circles; their paths are typically ovals (ellipses). The perigee is the satellite’s closest point to Earth in its orbit, and the apogee is its farthest point. These are usually given in kilometers. For the ISS, the apogee and perigee are very close – perhaps 418 km by 420 km – indicating a nearly circular orbit.
• Orbital Period: This is simply the time it takes for the satellite to complete one full orbit around the Earth. For the ISS in Low Earth Orbit, this is about 93 minutes. For a satellite in distant Geostationary Orbit, the period is 24 hours, which is why it appears to “stand still” over one spot on the equator.

Public & Commercial Web Resources: Visualizing the Data

While Space-Track.org provides the raw data, a rich ecosystem of third-party websites and services translates that data into user-friendly, visual, and predictive tools. These are often the best starting points for anyone interested in satellite tracking.

CelesTrak

For decades, Celestrak has been a pillar of the satellite tracking community. Operated by Dr. T.S. Kelso-Seiler, an expert in astrodynamics, CelesTrak is an analytical and data distribution service. It pulls the raw TLEs from Space-Track.org but then cleans, curates, and organizes them in ways that are much more useful for specific tasks.

Instead of just offering one massive catalog, CelesTrak provides “special event” and “special interest” data sets. For example, a user can download a single file containing the TLEs for:

• All active weather satellites.
• All satellites from a specific country (e.t., “Chinese Satellites”).
• All satellites from the Starlink constellation.
• Debris from a specific anti-satellite (ASAT) test.
• The group of satellites for a specific upcoming launch.

This curation saves researchers and hobbyists a significant amount of time. CelesTrak is also more than just a data provider. It features a powerful, web-based 3D orbit visualization tool called “OrbitViz,” which can plot the path of any satellite in the catalog. It also provides excellent educational resources explaining the fundamentals of orbital mechanics.

CelesTrak is an indispensable bridge between the raw, technical data of Space-Track.org and the practical needs of the public.

Heavens-Above

For the amateur satellite spotter, Heavens-Above is one of the most popular and enduring resources on the web. Its primary function is not just to show you where a satellite is, but to tell you when and where you can see it from your specific location.

A user visits the site, enters their city or coordinates, and Heavens-Above generates a customized list of upcoming satellite passes. It focuses on the brightest objects, providing predictions for:

• The International Space Station (ISS): It will list the exact time, duration, and path a user can watch the ISS glide across their sky.
• Starlink “Trains”: It provides predictions for the newly-launched batches of Starlink satellites, which are often visible as a string of lights before they spread out into their final orbits.
• Bright Satellites: It catalogs other visible objects, such as the Hubble Space Telescope or large rocket bodies.

Heavens-Above also generates detailed sky charts for each pass, showing the satellite’s path against the backdrop of constellations. It once famously tracked “Iridium flares,” which were bright flashes of light caused by sunlight glinting off the antennas of the first-generation Iridium satellite constellation. As those satellites have been deorbited and replaced by Iridium Communications, these flares are no longer a common sight, but the site remains the top resource for visual spotting.

N2YO.com

N2YO.com is another widely used, user-friendly tracking website that provides a great real-time view of orbital traffic. Its homepage features a 2D map showing the current position and ground track of thousands of satellites. It allows users to search for any object in the catalog and get its real-time data, including altitude, speed, and position.

Like Heavens-Above, N2YO.com takes a user’s location to provide 10-day predictions for visible passes of major satellites like the ISS and Starlink groups. It also features a “What’s up?” section that provides a quick-look dashboard of objects currently passing overhead.

The site is popular because it strikes a balance between providing detailed technical data (like the raw TLEs) and offering simple, real-time visualization that is easy for anyone to understand. It also tracks satellite “owners,” allowing users to filter the map by categories like military satellites, weather satellites, or satellites operated by a specific country.

Commercial Platforms: LeoLabs and COMSPOC

In recent years, the private sector has begun to build its own sensor networks to supplement the data from the U.s. government. These companies provide commercial Space Situational Awareness (SSA) services, often at a much higher precision or frequency than the public data.

• LeoLabs: This company has built its own global network of advanced, phased-array radars. Its focus is on Low Earth Orbit, the most congested region of space. LeoLabs provides high-precision, real-time tracking data and collision avoidance services to satellite operators. While its primary products are commercial, LeoLabs often shares visualizations and data on significant events, such as new launches, on-orbit breakups, or reentries. It also offers a “LEOmap” visualization on its website showing the objects it’s tracking.
• COMSPOC: This company, a part of Analytical Graphics, Inc. (Ansys), focuses on both LEO and the more distant Geostationary Orbit (GEO). It operates a network of optical telescopes to track GEO satellites, which are often too far for radar. COMSPOC provides advanced SSA services, analysis, and data to commercial and government operators. It also maintains a public-facing visualization tool, “Spacebook,” which provides a free, 3D map of the GEO belt and other objects, along with a catalog of space events.

These commercial platforms represent the future of space tracking, where a mix of public and private sensors will work together to catalog the growing orbital population.

Specialized & Academic Databases: The Deeper Dives

Beyond real-time tracking, several organizations maintain curated databases that focus on what a satellite is and what it is for. These are less about “where is it right now” and more about “what is the state of the orbital population.”

The UN Register of Objects Launched into Outer Space

The United Nations Office for Outer Space Affairs (UNOOSA) maintains the official “Register of Objects Launched into Outer Space.” Under the 1976 Registration Convention, countries are required (though not all comply perfectly) to provide the UN with information about any object they launch into space.

This database is a foundational, legal, and diplomatic record of the space-faring age. It is not a real-time tracking tool. Instead, it’s an archive. For most objects, a user can find:

• State of Registry: The launching country.
• International Designator: The COSPAR ID (e.g., 1998-067A).
• Date and Location of Launch.
• Basic Orbital Parameters: The nodal period, inclination, apogee, and perigee at the time of launch.
• General Function: A brief description of the satellite’s mission, such as “Earth observation” or “telecommunications.”

The UNOOSA register is the official, global “birth certificate” for a satellite. It’s an excellent resource for historical research, policy analysis, and understanding which nations are responsible for which objects.

The Union of Concerned Scientists (UCS) Satellite Database

For decades, the Union of Concerned Scientists (UCS) has maintained one of the most valuable public databases for analyzing the purpose of satellites. This resource, which is updated regularly, is a downloadable spreadsheet that can be used by researchers, journalists, and the public.

The UCS Satellite Database filters and curates the satellite catalog to include only operational satellites. It then adds a wealth of hand-curated data that is not available from the technical tracking sites. This is where a user can go to answer “big picture” questions.

The database includes fields for:

• Operator/Owner: It distinguishes between the owner (who paid for it) and the operator (who flies it).
• Country of Operator: Which nation (or nations, in a joint mission) controls the satellite.
• Users: This is a key category. The UCS database classifies satellites by their primary users: Commercial, Government, Military, or Civil. A NASA science satellite is “Government,” while a NOAA weather satellite is “Civil.”
• Purpose: This is the most detailed category, breaking down missions into types like Communications, Earth Observation, Space Science, Navigation, or Technology Development.
• Detailed Characteristics: It also includes data on launch mass, expected lifetime, and contractor.

If a person wants to know how many military reconnaissance satellites China operates, or how many commercial communication satellites are in geostationary orbit, the UCS database is the best place to find the answer. It is a powerful tool for economic, policy, and security analysis.

Jonathan’s Space Report

For the truly dedicated space enthusiast or researcher, Jonathan’s Space Report (JSR) is a legendary resource. It’s not a database or a visualizer but a newsletter-style text report compiled by Dr. Jonathan McDowell, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics.

Dr. McDowell meticulously cross-references official launch announcements, academic papers, government data, and amateur observations to create one of the most comprehensive and accurate public logs of all space activity. JSR is where you go for the details that fall through the cracks of other databases.

JSR provides detailed reports on:

• Every launch: It lists the payloads, their intended orbits, and their identifiers, often correcting or clarifying official reports.
• Suborbital launches: It’s one of the few resources that also tracks high-altitude research rockets.
• Reentries: It provides detailed analysis of reentering objects.
• On-orbit events: It logs when satellites maneuver, deploy subsatellites, or fail.

It also includes a “master satellite catalog” that is a scholarly alternative to the official government list, often including objects or details not found elsewhere. It is a text-heavy, deeply academic resource that is respected as a primary source by the entire space community.

The European Space Agency (ESA) DISCOS

The European Space Agency (ESA) maintains its own powerful database called DISCOS (Database and Information System Characterising Objects in Space). This database serves as the backbone for ESA’s own space debris and situational awareness office.

DISCOS merges TLE data with a wealth of other information, including launch details, satellite physical characteristics (size, mass, shape), mission objectives, and ownership. It is one of the most comprehensive technical databases available.

Access to DISCOS is more restricted than the other resources on this list. It is free for users from ESA member states, research institutions, and government entities, but requires a registration and approval process. It is a professional-grade tool used for operational collision avoidance, reentry analysis, and debris modeling.

The Data of Decay: Tracking Deorbited Objects

A satellite’s life doesn’t just end; it concludes with a deorbit and reentry. Tracking this final phase is a distinct and challenging part of satellite data management. Objects in Low Earth Orbit are subject to tiny amounts of atmospheric drag, which slowly but surely pulls them down. This orbital decay is highly unpredictable.

An object’s drag depends on its size, mass, and shape. It’s also heavily influenced by solar activity. When the sun is active, it heats and expands Earth’s upper atmosphere, increasing drag and pulling satellites down faster.

Predicting exactly when and where a large object will reenter is almost impossible until the final few hours. The reentry “window” can be days long, and in that time, the object circles the globe dozens of times. A 10-minute error in the time prediction can mean the debris falls on an entirely different continent.

Several resources specialize in this reentry data:

• Space-Track.org: As the official catalog, it provides “decayed” status for all objects that have reentered. For upcoming, high-interest reentries, it issues TIP messages with the latest prediction windows.
• The Aerospace Corporation: This U.S. federally funded research and development center provides indispensable analysis on space operations. Its “Reentry and Debris” page is a key public resource. For major reentry events (like large rocket bodies or defunct satellites), they provide detailed predictions, maps of the potential reentry path, and clear explanations of the risk to the public.
• Celestrak: Dr. Kelso-Seiler provides curated TLEs and analysis for decaying objects, helping the community track them in their final days.
• Jonathan’s Space Report: This is an excellent source for historical analysis of past reentries, logging the confirmed time and location of debris impacts, if any.

Tracking deorbited objects is less about real-time position and more about probabilistic prediction. It’s a “when and where will it fall” problem, and these resources provide the best available public data.

Summary

The digital ecosystem for tracking satellites is as layered and complex as the orbital environment itself. It ranges from the foundational, raw data catalog maintained by the U.S. military to highly specialized academic databases and user-friendly visual trackers.

For the non-technical user, resources like Heavens-Above and N2YO.com provide a fantastic and accessible window into the traffic overhead, allowing anyone to spot the ISS or a Starlink train.

For the enthusiast or researcher, CelesTrak provides the essential, curated data sets needed to power other applications and analyses.

For policy experts, journalists, and economists, the UCS Satellite Database and the UNOOSA Register provide the “what and why,” cataloging the human purpose and ownership behind the objects in orbit.

And at the bottom of it all, Space-Track.org serves as the primary, authoritative library for the entire public-facing space-tracking world. Together, these resources democratize access to the high frontier, transforming the thousands of satellites in orbit from abstract concepts into a catalog of traceable, understandable, and visible objects.