International Designator

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The International Designator (or NSSDC ID) is an international naming convention for satellites. It consists of the launch year, a 3-digit incrementing launch number of that year and up to a 3-letter code representing the sequential id of a piece in a launch. Only publicly known satellites are designated. Some military satellites are not cataloged and are not reflected in the "per year incrementing" launch number.

For example, 1957-001A is Sputnik 1's launch vehicle and 1957-001B is the actual Sputnik 1 satellite. The number reveals that it was launched in 1957 and that it was the first launch made that year. Another example is 1990-037B, the Hubble Space Telescope, which was the 37th known successful launch world wide in 1990. 1990-037A is the Space Shuttle Discovery on mission STS-31, which was to carry the Hubble telescope into space.

Launch failures are not given standard NSSDC IDs. They are instead cataloged with "arbitrary" designations, for example VAGSL1 for the satellite Vanguard SLV 1.

The designation system has been generally known as the COSPAR system, after a true international organization. This group subsumed the first designation system, devised at Harvard University in 1958. And that system used minuscule letters of the Greek alphabet to designate artificial satellites. For example, Sputnik 1 was designated 1957α. In 1963, the system was changed to use numerals instead, but its retroactive application for ease of computerized reference was not immediate. For example, the quarterly publication TRW Space Log of 1969 had satellites orbited before 1963 listed by Greek letters and those during and after by numerals.

The catalog is administered in the United States by the National Space Science Data Center (NSSDC), part of NASA.