The Satellite Catalog Number (SATCAT, also known as NORAD (North American Aerospace Defense) Catalog Number, NORAD ID, USSPACECOM object number or simply catalog number, among similar variants) is a sequential nine-digit number assigned by the United States Space Command (USSPACECOM) in the order of launch or discovery to all artificial objects in the orbits of Earth and those that left Earth's orbit. [1] The first catalogued object, catalog number 1, is the Sputnik 1 launch vehicle, with the Sputnik 1 satellite having been assigned catalog number 2. [2] Objects that fail to orbit or orbit for a short time are not catalogued. [3] The minimum object size in the catalog is 10 centimetres (3.9 in) in diameter. [4] As of October 21,2023 [update] , the catalog listed 58,010 objects, including 16,645 satellites that had been launched into orbit since 1957 of which 8,936 were still active. [5] 25,717 of the objects were well tracked while 2,055 were lost. [6] In addition USSPACECOM was also tracking 16,600 analyst objects. [7] Analyst objects are variably tracked and in constant flux, so their catalog and element set data are not published. As of September 12,2023 [update] ESA estimated there were about 36,500 pieces of orbiting debris that are large enough for USSPACECOM to track. [8]
Permanently catalogued objects are assigned a number from 1 to 69,999 [9] or above 99,999. Space-Track is expected to start publishing objects greater than 99,999 in 2020 [10] starting with debris discovered by Space Fence. [11]
Space Command shares the catalog via space-track.org, [12] which is maintained by the 18th Space Defense Squadron (18 SDS).
Initially, the catalog was maintained by NORAD. From 1985 onwards, USSPACECOM was tasked to detect, track, identify, and maintain a catalog of all human-made objects in Earth orbit. [13] In 2002, USSPACECOM was disestablished and merged with the United States Strategic Command (USSTRATCOM). However, USSPACECOM was reestablished in 2019. [14]
Before 2020, the catalog number was limited to five digits due to the TLE format limitation. In 2020, Space-Track started to provide data in CCSDS OMM (Orbit Mean-Elements Message) format, which increased the maximum catalog number to 999,999,999. [11]
The United States Space Surveillance Network (SSN) detects, tracks, catalogs and identifies artificial objects orbiting Earth, e.g. active/inactive satellites, spent rocket bodies, or fragmentation debris. The system is the responsibility of United States Space Command and operated by the United States Space Force.
A two-line element set (TLE) is a data format encoding a list of orbital elements of an Earth-orbiting object for a given point in time, the epoch. Using a suitable prediction formula, the state at any point in the past or future can be estimated to some accuracy. The TLE data representation is specific to the simplified perturbations models, so any algorithm using a TLE as a data source must implement one of the SGP models to correctly compute the state at a time of interest. TLEs can describe the trajectories only of Earth-orbiting objects. TLEs are widely used as input for projecting the future orbital tracks of space debris for purposes of characterizing "future debris events to support risk analysis, close approach analysis, collision avoidance maneuvering" and forensic analysis.
Simplified perturbations models are a set of five mathematical models used to calculate orbital state vectors of satellites and space debris relative to the Earth-centered inertial coordinate system. This set of models is often referred to collectively as SGP4 due to the frequency of use of that model particularly with two-line element sets produced by NORAD and NASA.
The Kessler syndrome, proposed by NASA scientist Donald J. Kessler in 1978, is a scenario in which the density of objects in low Earth orbit (LEO) due to space pollution is numerous enough that collisions between objects could cause a cascade in which each collision generates space debris that increases the likelihood of further collisions. In 2009, Kessler wrote that modeling results had concluded that the debris environment was already unstable, "such that any attempt to achieve a growth-free small debris environment by eliminating sources of past debris will likely fail because fragments from future collisions will be generated faster than atmospheric drag will remove them". One implication is that the distribution of debris in orbit could render space activities and the use of satellites in specific orbital ranges difficult for many generations.
This is the timeline of known spaceflights, both crewed and uncrewed, sorted chronologically by launch date. Owing to its large size, the timeline is split into smaller articles, one for each year since 1951. There is a separate list for all flights that occurred before 1951.
The year 1967 in spaceflight saw the most orbital launches of the 20th century and more than any other year until 2021, including that of the first Australian satellite, WRESAT, which was launched from the Woomera Test Range atop an American Sparta rocket. The United States National Space Science Data Center catalogued 172 spacecraft placed into orbit by launches which occurred in 1967.
Explorer 1 was the first American satellite to reach orbit on 31 January 1958.
The International Designator, also known as COSPAR ID, is an international identifier assigned to artificial objects in space. It consists of the launch year, a three-digit incrementing launch number of that year and up to a three-letter code representing the sequential identifier of a piece in a launch. In TLE format the first two digits of the year and the dash are dropped.
This article outlines notable events occurring in 2000 in spaceflight, including major launches and EVAs.
This article outlines notable events occurring in 1995 in spaceflight, including major launches and EVAs.
In 1975 several notable events happened in spaceflight such as the launch and arrival at Venus of Venera 9 and 10, the launch to Mars of the Viking orbiter/landers missions, the joint Apollo–Soyuz Test Project, and the launch of satellite Aryabhatta.
The following is an outline of 1976 in spaceflight.
The following is an outline of 1987 in spaceflight.
This is a list of spaceflights launched between January and June 1961. For launches between July and December, see 1961 in spaceflight (July–December). For an overview of the whole year, see 1961 in spaceflight.
This is a list of spaceflights launched between October and December 1964. For launches in the rest of the year, see 1964 in spaceflight (January–March), 1964 in spaceflight (April–June) and 1964 in spaceflight (July–September). For an overview of the whole year, see 1964 in spaceflight.
In 2015, the maiden spaceflights of the Chinese Long March 6 and Long March 11 launch vehicles took place.
Kosmos 2499 was a Russian satellite orbiting the Earth, before breaking up on January 4, 2023.
This article documents expected notable spaceflight events during the 2020s.
Q: What criteria are used to determine whether an orbiting object should receive a catalogue number and International Designation? A: We must be able to determine who it belongs to, what launch it correlates to, and the object must be able to be maintained (tracked well).
10 centimeter diameter or "softball size" is the typical minimum size object that current sensors can track and 18 SPCS maintains in the catalog.