December 28, 1973 · about 1,505 km up · 52 years ago · counted by launch designator
196 fragments still on orbit
The first of the Delta failures: a second stage exploded seven weeks after launching the NOAA 3 weather satellite, from propellant left in its tanks after shutdown.
The event took place on December 28, 1973 at roughly 1,505 km. The first of the Delta failures: a second stage exploded seven weeks after launching the NOAA 3 weather satellite, from propellant left in its tanks after shutdown. What the catalogue has recorded since is 221 trackable fragments — pieces large enough for ground radar to find and follow, which in practice means roughly 10 cm and up. Everything smaller is up there too and is not counted by anyone, here or elsewhere; a fleck of paint at orbital speed carries about the energy of a rifle round, and no public catalogue can see it.
52 years later, 88.7% of it is still in orbit. The fragments now sit between 546 and 1,993 km, with the middle of the cloud at 1,501 km — spread by the breakup into a band far wider than the original orbit, and thinning only slowly.
Air drag is what cleans orbit, and there is almost none of it above about 600 km. Compare this cloud with Cosmos 1408, the furthest away in altitude of the 16 plotted here — a gap of 1,113 km. Delta (1973) sits at 1,501 km and is 11.3% gone; Cosmos 1408 sits at 388 km and is 99.7% gone — and it happened in 2021, later. Higher is why this one is staying, and age has very little to do with it.
That is the whole argument of this layer, and it is the reason an anti-satellite test at 800 km is a fundamentally different act from the same test at 400 km. One is cleaned up by the atmosphere within a decade or two. The other is a hazard your grandchildren will be flying through.
This one cloud is 1.6% of every piece of debris currently tracked around Earth — 196 of 12,520. It ranks #9 of the 16 named clouds plotted on this layer. The named clouds are not the whole catalogue, and the hub says so plainly: most tracked debris traces back to launches with no famous name attached, including two rocket upper stages that each left behind more than this page’s smallest cloud.
Counts and altitudes for this cloud were derived from the CelesTrak SATCAT — the public satellite catalogue — read July 26, 2026. Live positions on the globe come from CelesTrak GP element sets, propagated in your browser. “On orbit” means no decay date on file; “burned up” means a decay date has been recorded. Fragments reenter continually, so these figures are a snapshot of one day rather than a running total. This cloud’s fragments are counted by launch designator — every catalogued fragment sharing this launch’s ID, which is how the catalogue groups breakups that have no curated group of their own. Other figures on this layer are counted by a different method, and the two do not produce identical totals — a launch can carry several satellites, so a fragment’s attributed parent is not always its launch. Neither is wrong; they answer slightly different questions. The catalogue-wide total was read live on July 27, 2026.