Satellites

Satellites#

Reference of satellite constellations, positioning systems, and the data sources that catalog them. The orbital population exceeds 10,000 active satellites in 2026 (Starlink alone is ~6,000); this page is the lookup, not the catalog.

For RF allocations, see Radio Frequencies. For imagery sources, see Map Sources. For positioning math, see Triangulation.

Orbits#

Class

Notes

LEO (low)

160 - 2,000 km. Most imaging, comms constellations (Starlink, OneWeb, Iridium, Globalstar, Planet, Maxar, BlackSky), ISS (~400).

MEO (medium)

2,000 - 35,786 km. GNSS (GPS at 20,200; GLONASS at 19,100; Galileo at 23,222; Beidou MEO at 21,500); O3b (mPower) at 8,062.

GEO (geostationary)

35,786 km equatorial; broadcast, weather (GOES, METEOSAT, Himawari), military comms.

HEO (highly elliptical)

Molniya (~12 h) for high-latitude coverage; Tundra (~24 h).

GTO

Transfer orbit; not stable parking.

SSO (sun-synchronous)

Polar LEO with constant local-solar-time crossing; nearly all earth-observation imagery.

Cislunar / lunar

NRHO (Gateway), DRO; growing cislunar operations.

GNSS constellations#

System

Sats

Notes

GPS (US)

~31

L1 1575.42, L2 1227.6, L5 1176.45 MHz; civil + military signals.

GLONASS (RU)

~24

L1 ~1602, L2 ~1246; FDMA legacy + CDMA modern.

Galileo (EU)

~30

E1 1575.42, E5a 1176, E5b 1207, E6 1278; high-accuracy service.

Beidou / BDS (CN)

~45

B1 1561.098, B2 1207, B3 1268; global since 2020.

NavIC / IRNSS (IN)

7

Regional; L5 + S-band (2492.028).

QZSS (JP)

7

Regional augmentation; HEO + GEO.

SBAS

WAAS (US), EGNOS (EU), MSAS (JP), GAGAN (IN), KASS (KR), BDSBAS (CN), SDCM (RU); GEO augmentation.

Major LEO constellations#

Constellation

Sats

Notes

Starlink (SpaceX)

~6,500

Broadband internet; ~550 km; v1, v1.5, v2 mini, v2 full.

OneWeb / Eutelsat

~650

Broadband; ~1,200 km.

Project Kuiper (Amazon)

(planned 3,236)

Broadband; deployment 2024+.

Iridium NEXT

66+9

L-band voice / data; SAR (Cospas-Sarsat 406).

Globalstar

48

L/S-band voice / data.

Inmarsat (mostly GEO)

14

L-band voice / data; safety services.

Planet (Doves + SkySat)

~200

Sub-meter imaging, daily-revisit.

Maxar (WorldView+)

6

Sub-meter commercial imagery.

BlackSky

14

Hourly revisit imaging.

Capella Space

8

X-band SAR.

ICEYE

30+

X-band SAR.

Umbra

7

X-band SAR.

HawkEye 360

21

RF geolocation.

Spire (LEMUR)

100+

AIS / ADS-B / GNSS-RO weather.

Swarm Tech

170+

Low-bandwidth IoT.

Hiber, Astrocast, Lacuna, Kepler

Other IoT sat networks.

GHGSat

10+

Methane plume detection.

Skykraft, Aireon

Aviation tracking.

Cospas-Sarsat (LEO)

5

SAR (406 MHz) on NOAA + Sarsat.

GEO comms / broadcast#

Operator

Sats

Notes

Intelsat

~50

Global C / Ku / Ka.

SES

~70

Includes O3b mPower MEO.

Eutelsat (incl. OneWeb)

GEO + LEO

Hybrid since 2023.

Viasat (incl. Inmarsat)

Ka-band

Broadband + L-band safety.

Hughes / Echostar

Jupiter-3.

SpaceX (Starshield)

Government variants of Starlink.

Telesat (Lightspeed)

Polar LEO

Under build.

Earth observation#

Program

Sats

Notes

Sentinel-1 (ESA)

2

C-band SAR; ~6-day revisit.

Sentinel-2 (ESA)

2

10 m optical; ~5-day revisit; free.

Sentinel-3 (ESA)

2

Ocean / land surface.

Sentinel-5P / 5

Atmospheric (NO2, CH4, etc.).

Sentinel-6

1

Sea-level altimetry.

Landsat 8 / 9 (USGS )

2

30 m optical; 16-day revisit; free.

MODIS (Terra/Aqua)

2

250 m daily; aging (early 2000s).

VIIRS (Suomi-NPP, N

OAA-20/

  1. 3 Daily; nighttime lights.

GOES (NOAA)

4

GEO weather, US.

METEOSAT / MTG

2+

GEO weather, EU.

Himawari (JP)

2

GEO weather, Asia.

GeoStar (China)

FY series + Gaofen.

RADARSAT-2 / RCM

3

Canadian SAR.

ICEYE / Capella / Umbra

See above.

SuperView (CN)

8

0.5 m optical (commercial).

Pleiades / Pleiades Neo (FR)

4 + 4

Sub-m optical.

WorldView / GeoEye (Maxar)

6

Sub-m optical.

Tracking and catalogs#

Source

Notes

Space-Track.org

USSF 18th SDS; the authoritative TLE catalog.

Celestrak

Mirrors Space-Track + curated lists; the operator-friendly front end.

N2YO

Web tracker.

Heavens-Above

Pass predictions; visual obs.

Stuff in Space

3-D real-time visualization.

LeoLabs

Commercial radar tracking; debris focus.

EUSST

EU Space Surveillance & Tracking.

Russian / NORAD

Independent radar networks.

SatNOGS

Crowdsourced ground-station network for amateur sats.

TLEs (Two-Line Element sets)

The standard orbit format; produced by Space-Track and mirrored everywhere.

SGP4

The propagator for TLEs; in pyephem, skyfield, sgp4.

GP / OMM (XML)

Newer machine-readable orbit format.

Space-Data Coord.

Astrodynamics standards body.

SISC / OSC

International conjunction-warning hubs.

Status / health#

Service

Notes

GPS NANUs

NAVCEN notice-to-users; outages, maintenance.

GPS Performance

USCG Navcen + ISA reports.

GLONASS Status

IAC Russia.

Galileo Status

European GNSS Agency Service Center.

Beidou Status

China Satellite Navigation Office.

NORAD breakup

Periodic; SOCRATES catalog.

ESA Space Debris

ESA Space Debris Office; ESA Space Environment Report.

NASA ODPO

Orbital Debris Program Office.

Tooling#

Library

Notes

Skyfield (Python)

Modern astronomy + sat propagation.

PyEphem

Older astronomy library.

sgp4 (Python / C)

TLE propagator.

GMAT

NASA mission-design analysis tool.

STK / Ansys SatLab

Commercial.

Orekit (Java)

Industrial astrodynamics library.

poliastro (Python)

Astrodynamics teaching / research.

Cosmos / GMAT

mission analysis.

SatNOGS Network

receive amateur sat passes from your station or borrow others’.

gpredict

Linux sat-tracking GUI.

JS9, Stellarium

visualization.

Operator notes#

  • TLEs decay, low-LEO TLEs are usable for ~3-7 days, then drift; refresh from Space-Track.

  • Maneuvers, TLE propagation is invalid after thrust.

  • GP catalog is moving to OMM (XML) and CCSDS standards; legacy TLE remains supported.

  • Conjunction risk, LeoLabs and EUSST publish miss-distance data; commercial operators screen daily.

  • Authorization, transmitting to satellites is licensed (FCC OET / Part 25 in US, Ofcom in UK, etc.). Receive-only is typically open.

  • Imagery licensing, raw or near-raw commercial imagery rights vary; per-pixel licenses are common.

  • Constellation churn, Starlink replaces ~5-year-life satellites continuously; the “active” count moves daily.

References#

Contents