Scrub the year slider to watch tracked debris and satellites grow in low Earth orbit, or click an event button to jump straight to a real fragmentation event.
Each of the four altitude bands shown is exaggerated in spacing for readability - real low-Earth-orbit shells sit close together relative to Earth's size. Dot counts scale with the year slider and represent a proportional share of the cited totals, not a literal one-dot-per-object count.
Drag to orbit the scene and scroll or pinch to zoom. The 600-1000km band is where ESA's 2025 analysis found fragmentation currently outpaces atmospheric decay.
Space Debris & Kessler Syndrome 3D Explorer
Scrub the year slider from 2007 to 2026 to watch tracked debris and satellites accumulate across four altitude bands in low Earth orbit (LEO), or jump straight to a real fragmentation event with the two event buttons.
The Kessler syndrome, named for NASA scientist Donald Kessler who described it in 1978, is the debris-density threshold beyond which collisions generate new debris faster than natural atmospheric decay can remove it. The 600-1000km band shown in this scene is the altitude range ESA's 2025 analysis flagged as already past that tipping point for parts of the current catalogue.
- Move the year slider to see the tracked-object count and dot density change between 2007 and 2026
- Click "2007: Fengyun-1C test" or "2009: Iridium-Cosmos collision" to jump to that year and read what happened
- Click "Highlight 550km Starlink shell" to see the mega-constellation altitude band called out against the others
- Drag to orbit the scene and scroll or pinch to zoom
- Runs fully in the browser with the vendored three.js engine - no account, no upload
| Metric | 2007 | 2026 |
|---|---|---|
| Tracked objects >10cm (LEO) | about 13,000 | more than 40,000 (about 11,000 active satellites) |
| Untracked fragments 1-10cm (MASTER-8 model) | not modeled at this granularity | about 1.2 million |
| Untracked fragments <1cm (MASTER-8 model) | not modeled at this granularity | more than 140 million |
| Total tracked mass in orbit | lower | more than 15,000 tonnes, concentrated in LEO |
These figures come from the ESA Space Environment Report (esa.int/Space_Safety/Space_Debris) and the eoPortal Orbital Debris reference (eoportal.org). Source figures for total tracked-object counts vary noticeably across secondary sources online (values from roughly 29,000 to 44,800 all circulate); this page cites only the ESA-official and eoPortal figures rather than averaging conflicting secondary numbers. The 2007 Fengyun-1C anti-satellite test alone created more than 3,500 tracked fragments in a single event; the 2009 Iridium-33 / Cosmos-2251 collision is the reference case for an accidental collision generating trackable debris. ESA's Space Environment Report 2025 finding is that even with zero further launches, the tracked-object count keeps rising for 200+ years, because fragmentation currently outpaces atmospheric decay at several LEO altitude bands between about 520km and 1000km.
This page shows debris density and growth over time. For a single real spacecraft's live position, see ISS Orbit Tracker 3D Explorer. For how LEO, MEO, GEO, and highly-elliptical orbits differ as altitude regimes, see Satellite Orbit Classes 3D Explorer. For Earth's natural radiation belts (not artificial debris), see Van Allen Belts 3D Explorer.
Everything renders on your device with WebGL. The 3D engine loads once (about 0.7 MB) and is cached.
This is an educational approximation, not a physical simulation: the year slider draws a straight line between the two published 2007 and 2026 totals, which smooths over real step-jumps like the two historical events shown; individual dot positions within each altitude band are randomly scattered for legibility, not the real catalogued positions of specific tracked objects; and the four altitude bands are drawn with exaggerated spacing so they are visually distinguishable, not to true scale. The cited totals, event details, and altitude-band ordering are accurate to the referenced sources.
Frequently Asked Questions
What is the Kessler syndrome?
It is the debris-density threshold beyond which collisions in orbit generate new debris faster than natural atmospheric decay can remove it. NASA scientist Donald Kessler described the concept in 1978. ESA's 2025 analysis found parts of the 600-1000km band are already past that tipping point.
How many objects are tracked in orbit?
ESA's space surveillance networks track more than 40,000 objects larger than 10cm as of 2026, including about 11,000 active satellites. ESA's MASTER-8 statistical model separately estimates about 1.2 million untracked fragments 1-10cm and more than 140 million fragments smaller than 1cm.
How much has the debris count grown since 2007?
The tracked LEO object count grew from about 13,000 in 2007 to about 44,800 in 2026 per the ESA Space Environment Report. This page's year slider draws a straight line between those two published figures for legibility - the real growth included step-jumps from events like the ones covered by the two event buttons.
What happened in the 2007 Fengyun-1C event?
China's 2007 Fengyun-1C anti-satellite missile test intentionally destroyed a satellite in a roughly 850km orbit, creating more than 3,500 tracked fragments in a single event - among the largest debris-generating events on record.
What happened in the 2009 Iridium-Cosmos collision?
In February 2009 the active Iridium-33 satellite and the defunct Cosmos-2251 satellite collided accidentally near 790km altitude. It is the reference case for an unintentional collision generating trackable debris and a key data point behind Kessler-syndrome cascade-risk analysis.
Why does the 550km Starlink shell get its own highlight?
The 500-600km band hosts large satellite mega-constellations such as Starlink alongside debris, illustrating how a densely populated operational shell and debris density can coexist at the same altitude range.
Does this page simulate real orbital mechanics?
No. It is an educational approximation: dot positions within each altitude band are randomly scattered for legibility, not real catalogued positions, and altitude-band spacing is exaggerated so the bands are visually distinguishable. The cited totals and event details are accurate to the referenced ESA and eoPortal sources.