United States Space Surveillance Network

The United States Space Surveillance Network (SSN) detects, tracks, identifies, and catalogs artificial objects orbiting Earth. Examples include satellites, abandoned launch vehicle stages, and other space debris. The SSN is the responsibility of United States Space Command and is operated by the United States Space Force. Its functions include:

Predict when and where a decaying space object will re-enter the Earth's atmosphere;

Prevent a returning space object, which to radar looks like a missile, from triggering a false alarm in missile-attack warning sensors of the U.S. and other countries;

Chart the present position of space objects and plot their anticipated orbital paths;

Detect new artificial objects in space;

Map objects traveling in Earth orbit;

Produce a running catalog of artificial space objects;

Determine ownership of a re-entering space object;

Command and control of future U.S. anti-satellite weapon (ASAT) systems.

The SSN includes dedicated, collateral, and contributing electro-optical, passive radio frequency (RF) and radar sensors. It provides space object cataloging and identification, satellite attack warning, timely notification to U.S. forces of satellite fly-over, space treaty monitoring, and scientific and technical intelligence gathering. The continued increase in satellite and orbital debris populations, as well as the increasing diversity in launch trajectories, non-standard orbits, and geosynchronous altitudes, necessitates continued modernization of the SSN to meet existing and future requirements and ensure their cost-effective supportability.

History

1957–1963

The first formalized effort by the US government to catalog satellites occurred at Project Space Track, later known as the National Space Surveillance Control Center (NSSCC), located at Hanscom Field in Bedford, Massachusetts. The procedures used at the NSSCC were first reported in 1959 and 1960 by Wahl, who was the technical director of the NSSCC. In 1960, under Project Space Track, Fitzpatrick and Findley developed detailed documentation of the procedures used at the NSSCC. Project Space Track began its history of satellite tracking from 1957 to 1961.

Early Space Track observations of satellites were collected at more than 150 individual sites, including radar stations, Baker–Nunn cameras, telescopes, radio receivers, and by citizens participating in the Operation Moonwatch program.