Ephem · orbital debris feed

Debris density, per 10 km altitude shell, refreshed nightly.

Name: Ephem — LEO debris density by altitude shell
Creator: Ephem
License: https://ephem.pages.dev/terms

Ephem's debris feed publishes objects-per-km³ for every 10 km × 5° latitude × 10° longitude bin in the 200–2,000 km altitude range. Numbers are computed nightly from the full CelesTrak active catalog using open-source SGP4. Methodology is public. Nothing is proprietary; the value is the delivery, the diff, and the sign-off, not the maths.

§1 What you get

Nightly density feed — one JSON envelope per altitude shell. Includes bin coordinates, object counts, and density.
Diff endpoint — added / removed / shell-crossed objects vs. the previous night. Machine-readable, ready for a Slack notifier.
Webhook subscriptions — subscribe to a shell + threshold, get an HTTPS POST when density crosses it.
Monthly PDF report — signed, versioned per-month digest with per-shell density and diff summary. Browse editions →
Open-source propagator — the exact SGP4 wrapper that produces the numbers, released under MIT.

§2 Notable shells

Altitude	Label	Character
400 km	ISS shell	Human spaceflight altitude. Very high atmospheric drag; anything not actively boosted decays within months.
500 km	Starlink Gen1 lower	Densest LEO congestion band as of 2026 — Starlink Gen1 primary shell alongside legacy Earth-observation birds.
550 km	Starlink primary	Nominal Starlink v1.5 shell. If you want a debris-density search-intent page, this is the one.
600 km	Sunsynch band	Lots of sunsynch Earth-observation payloads. Also secondary Starlink shells and rideshare payloads.
700 km	OneWeb secondary	Sparse; a few science payloads and secondary comms shells transit through here.
780 km	Iridium NEXT	Iridium NEXT primary shell. Cross-linked, near-pole, extreme regularity — one of the most predictable belt structures in LEO.
800 km	SL-16 debris field	Dominated by Zenit-2 rocket bodies. Chronic conjunction alerts here — the classic 'why we need ADR' altitude.
850 km	Historic sunsynch	Older sunsynch platforms; still populated by legacy Earth-observation missions and their upper stages.
1200 km	OneWeb primary	OneWeb Gen1 shell. Higher than Starlink, so slower decay — long-term congestion driver.
1400 km	Kessler-danger band	Frequently cited as the highest-risk band for cascading collisions given long orbital lifetime and current object density.

§3 Sample request

GET · https://ephem-api.YOUR-SUBDOMAIN.workers.dev/shell/density/550

curl -s https://ephem-api.YOUR-SUBDOMAIN.workers.dev/shell/density/550 \
  -H "Authorization: Bearer ek_live_..."

{
  "source": "CelesTrak+SGP4",
  "fetched_at": "2026-08-04T03:22:14.000Z",
  "valid_until": "2026-08-05T03:22:14.000Z",
  "data": {
    "altitude_km": 550,
    "bin_km": 10,
    "as_of": "2026-08-04T03:22:14.000Z",
    "bins": [
      { "altitude_km": 550, "latitude_deg": 42.5, "longitude_deg": -75, "objects": 4, "density_per_km3": 2.3e-11 },
      ...
    ],
    "total_objects": 1287
  }
}

Density is objects per km³ within one 10 km × 5° × 10° bin. Volume varies with cos(lat).

§4 Why this exists

Orbital debris data is not the bottleneck. The bottleneck for an insurance underwriter, a satellite operator, or an active-debris-removal (ADR) company is a defensible chain of custody: which catalog, which propagation model, which timestamp, which error bars, signed by whom, on what schedule. Ephem's answer is: CelesTrak active catalog, open-source SGP4 (satellite.js 5.x), UTC 03:17 nightly, ±10 km radial, published by Ephem Ltd. Everything is inspectable.

§5 Pricing

Tier	Price	For
Shell Basic	$500 / mo	Small operators and researchers. Density feed + monthly PDF.
Shell Pro	$2,000 / mo	Insurers and ADR companies. Custom shells + webhooks + Slack channel.
Enterprise	custom	Big operators and government. SLA, on-prem cache, dedicated support.

[ Request a methodology PDF → ]