Delta (rocket family) in the context of "Expendable launch system"

The Explorers Program is a NASA exploration program that provides flight opportunities for physics, geophysics, heliophysics, and astrophysics investigations from space. Launched in 1958, Explorer 1 was the first spacecraft of the United States to achieve orbit. Over 90 space missions have been launched since. Starting with Explorer 6, it has been operated by NASA, with regular collaboration with a variety of other institutions, including many international partners.

Launchers for the Explorers Program have included Juno I, Juno II, various Thor, Scout, Delta and Pegasus launch vehicles, and Falcon 9.

Thor was a US space launch vehicle derived from the PGM-17 Thor intermediate-range ballistic missile. The Thor rocket was the first member of the Delta rocket family of space launch vehicles. The last launch of a direct derivative of the Thor missile occurred in 2018 as the first stage of the final Delta II.

United Launch Alliance, LLC (ULA) is an American launch service provider formed in December 2006 as a joint venture between Lockheed Martin Space and Boeing Defense, Space & Security. The company designs, assembles, sells and launches rockets. The company uses rocket engines, solid rocket boosters, and other components supplied by other companies.

When founded, the company inherited the Atlas V rocket from Lockheed Martin and the Delta rocket family from Boeing. As of 2024, the Delta family has been retired and the Atlas V is in the process of being retired. ULA began development of the Vulcan Centaur in 2014 as replacement for both the Atlas and Delta rocket families. The Vulcan Centaur completed its maiden flight in January 2024.

Delta IV was a group of five expendable launch systems in the Delta rocket family. It flew 45 missions from 2002 to 2024. Originally designed by Boeing's Defense, Space and Security division for the Evolved Expendable Launch Vehicle (EELV) program, the Delta IV became a United Launch Alliance (ULA) product in 2006. The Delta IV was primarily a launch vehicle for military payloads for the United States Air Force (USAF), but was also used to launch a number of United States government non-military payloads and a single commercial satellite.

The Delta IV had two main versions, which allowed the family to cover a range of payload sizes and masses: Medium, which had four configurations, and Heavy. The final flight of a Medium configuration occurred in 2019. The final flight of Heavy was in April 2024.

Intelsat I (nicknamed Early Bird for the proverb "The early bird catches the worm") was the first commercial communications satellite to be placed in geosynchronous orbit, on April 6, 1965. It was built by the Space and Communications Group of Hughes Aircraft Company (later Hughes Space and Communications Company, and now Boeing Satellite Systems) for COMSAT, which activated it on June 28, 1965. It was based on the Syncom series of satellites that Hughes had previously built for NASA to demonstrate that communications via synchronous-orbit satellite were feasible. Its booster was a Thrust Augmented Delta (Delta D). After a series of maneuvers, it reached its geosynchronous orbital position over the Atlantic Ocean at 28° West longitude, where it was put into service.

It helped provide the first live TV coverage of a spacecraft splashdown, that of Gemini 6 in December 1965. Originally slated to operate for 18 months, Early Bird was in active service for 4 years and 4 months, being deactivated in January 1969, although it was briefly activated in June of that year to serve the Apollo 11 flight when the Atlantic Intelsat satellite failed. It was deactivated again in August 1969 and has been inactive since that time (except for a brief reactivation in 1990 to commemorate its 25th launch anniversary), although it remains in orbit.