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Silent. The Atlas-Agena D launch vehicle looks like an Atlas-Centaur because a Centaur-type payload shroud was used for this launch.
Originally a public domain film from NASA, slightly cropped to remove uneven edges, with the aspect ratio corrected, and one-pass brightness-contrast-color correction & mild video noise reduction applied.
https://en.wikipedia.org/wiki/Orbiting_Astronomical_Observatory
Wikipedia license: http://creativecommons.org/licenses/by-sa/3.0/
The Orbiting Astronomical Observatory (OAO) satellites were a series of four American space observatories launched by NASA between 1966 and 1972, which provided the first high-quality observations of many objects in ultraviolet light. Although two OAO missions were failures, the success of the other two increased awareness within the astronomical community of the benefits of space-based observations, and led to the instigation of the Hubble Space Telescope...
OAO-1
The first OAO was launched successfully on 8 April 1966, carrying instruments to detect ultraviolet, X-ray and gamma ray emission. Before the instruments could be activated, a power failure resulted in the termination of the mission after three days. The spacecraft was out of control, so that the solar panels could not be deployed to recharge the batteries that would supply power to the electrical and electronic equipment on board...
https://en.wikipedia.org/wiki/Atlas-Agena
The Atlas-Agena was an American expendable launch system derived from the SM-65 Atlas missile. It was a member of the Atlas family of rockets, and was launched 109 times between 1960 and 1978. It was used to launch the first five Mariner uncrewed probes to the planets Venus and Mars, and the Ranger and Lunar Orbiter uncrewed probes to the Moon. The upper stage was also used as an uncrewed orbital target vehicle for the Gemini crewed spacecraft to practice rendezvous and docking. However, the launch vehicle family was originally developed for the Air Force and most of its launches were classified DoD payloads.
The Atlas-Agena was a two-and-a-half-stage rocket, with a stage-and-a-half Atlas missile as the first stage, and an RM-81 Agena second stage. Initially, Atlas D missiles, redesignated as the LV-3, were used as the first stage. These were later replaced by the standardized Atlas SLV-3, and its derivatives, the SLV-3A and B. The final Atlas-Agena launch used an Atlas E/F.
The earliest Agena variant was the Agena A in 1959-60, which did not have restart capability. Most of these were flown on Thor-Agena boosters for the Discoverer program and only four used Atlases (Midas 1, Midas 2, Samos 1, and Samos 2), two of which failed.
Late in 1960, Lockheed introduced the uprated Agena B stage which was restartable and had longer propellant tanks for more burn time. It first flew on the Thor and did not make its maiden voyage on an Atlas for months, when Midas 3 launched on July 12, 1961. Atlas-Agenas were then used for DoD and NASA programs, but proved a reliability nightmare as one failure after another happened. In late 1962, after Ranger 5 suffered another booster malfunction (albeit a minor one that ground controllers were able to work around), NASA convened a review board... The board recommended improved quality control, better hardware, and also establishing one standardized launch vehicle for all space programs.
The end result was the Atlas SLV-3 and Agena D, standardized versions of the Atlas D core and Agena B which would be the same on every launch (at least as far as the Atlas was concerned, Agena Ds often still had customized setups, especially for DoD payloads). The Agena D first flew in July 1963 for DoD launches, but NASA continued using Agena Bs for the remaining Ranger missions. The Atlas SLV-3 meanwhile first flew in August 1964. Dozens of Atlas SLV-3/Agena D boosters were flown over the following years, mostly for the KH-7 Gambit program, also for a few NASA missions. The last Atlas-Agena was flown in 1978 to launch SEASAT, but on a repurposed Atlas F missile rather than the SLV-3.
Launches were conducted from Launch Complexes 12, 13 and 14 at the Cape Canaveral Air Force Station, and Launch Complexes 1 and 2 at Point Arguello (now SLC-3 and 4 at Vandenberg Air Force Base)...
OAO
Orbiting Astronomical Observatory was a series of NASA satellites flown between 1966 and 1972 for astronomy studies. The first OAO (launched April 8, 1966) used a one-off Atlas variant, mating an Agena D to the LV-3C variant of the Atlas and encased in a Centaur-type payload shroud. The remaining three launches used actual Atlas-Centaur vehicles...