Operations and Checkout Building

The Neil Armstrong Operations and Checkout Building (O&C) (previously known as the Manned Spacecraft Operations Building) is a historic building on Merritt Island, Florida, United States. The five-story structure is in the Industrial Area of NASA's Kennedy Space Center. Its has twin-block facilities that include the crew quarter dormitories for astronauts, suit-up preparations prior to their flights, and the other is a large spacecraft workshop used for manufacturing and checking activities on crewed spacecraft. On January 21, 2000, it was added to the U.S. National Register of Historic Places.

Apollo program
During planning and construction, it was known as the Operations and Checkout Building. When it was finished in 1964, it was renamed the Manned Spacecraft Operations Building and was used to process spacecraft in the Gemini and Apollo era. It was reverted back to the Operations and Checkout Building during the Shuttle program, known informally as the O&C.

Altitude test chambers
In 1965, a pair of altitude chambers were installed in the High Bay for testing the environmental and life support systems of both the Apollo Command/Service Module and Lunar Module at simulated altitudes of up to 250,000 ft. Each chamber is 58 ft high (with a clear working height of 28 ft) and an interior diameter of 33 ft, were human-rated, and capable of reaching the maximum altitude (minimum pressure) in one hour. These were used by the prime and backup crews of all crewed missions, from the ill-fated Apollo 1 in October 1966, through to the Apollo-Soyuz Test Project in July 1975.

Post-Apollo use
During the 1980s and 90s the O&C building was used to house and test Spacelab science modules before their flights aboard the Space Shuttle.

In the late 1990s and 2000s, some modules and trusses for the International Space Station were checked out in the building.

Artemis Program
On January 30, 2007, NASA held a ceremony to mark the transition of the building's high bay for use by the Constellation program. The building would serve as the final assembly facility for the Orion crew exploration vehicle. In preparation for the transition, the state of Florida provided funds to clear the facility of about 50 ST of steel stands, structures and equipment. Renovations totaling $55 million took place from June 2007 through January 2009, at which point Lockheed Martin became the operator of the facility for Orion production. The Orion spacecraft for Artemis 1 completed its assembly in this location and was moved to the Multi-Payload Processing Facility on January 16, 2021. The Orion spacecraft for Artemis 2 is under final testing in the building as of July, 2024.

The building was renamed to the Neil Armstrong Operations and Checkout Building in a ceremony on the 45th anniversary of Apollo 11 (2014).