Apollo Telescope Mount
A19830234000d.jpg (42446 bytes)
Source: SI 97-152557
A19830234000h.jpg (38722 bytes)
Source: Space History

Apollo Telescope Mount

The Apollo Telescope Mount (ATM) was the major scientific instrument aboard Skylab, which was put into earth orbit in May 1973 and operated for 8 months. ATM included eight major scientific instruments as well as a number of smaller experiments, and were designed to be operated by three sets of visiting astronauts. These instruments observed the sun in a broad range of the spectrum from the visual through the x-ray regions. ATM also included a white-light coronagraph, which examined the Sun's outermost atmosphere.

The ATM in the collection is a back-up to the one that was placed in orbit. It consists of three major sections: a 14-foot diameter sunshield, the sunward section of the instrument canister, and the heavy structural spar which carried the instruments within the canister. The ATM was designed and constructed at NASA's Marshall Space Flight Center. The backup ATM at MSFC was disassembled in 1982 and the canister, spar assembly and solar shield were transferred to NASM in September 1982. The canister and sunshield were then re-assembled at NASM and mounted in the Stars gallery against a mural depicting Skylab. It stayed on display until October 1997.


Canister: L: 336 cm (11 feet)
D: 244 cm (8 feet)
Solar Shield: D: 427 cm (14 feet)
        L: 244 cm (8 feet)


The major solar instruments are located on an eight sided cruciform optical bench which consists of two ten foot long intersecting perforated metal plates. This assembly, called the "spar" is nested inside a cylindrical canister that in turn is cradled in a complex frame called the "rack". The solar shield forms the base for the rack and the canister. The shield contains aperture doors for each instrument to protect against solar radiation and contamination from surrounding space. The outer structure is made of aluminum and is painted "Cadillac White" - a special highly reflective coating that is designed to outgas quickly and leave the ATM environment clean.


The Apollo Telescope Mount was the major scientific instrument aboard Skylab, which was put into earth orbit in May 1973. This first manned space observatory was operated over a period of eight months by three sets of astronauts. The entire ATM sat on top of the Skylab workshop when the system was launched and was rotated to its working position (orthogonal with respect to the workshop and the Multiple Docking Adapter, to which it was attached) after insertion into orbit. The eight major scientific instruments as well as a number of smaller experiments centered around the ATM were operated by the astronauts from within Skylab. In contrast to all previous solar observations from space, the instruments were not compromised by weight or power restrictions, nor by the need to telemeter observational data to ground stations. The major solar instruments were located on an eight sided optical bench which consisted of two ten-foot intersecting perforated metal plates. The instruments weighed some 2000 lb. each and required over one kilowatt of power - the total experiment power was 2 kilowatts, supplied by four 40-foot solar panels. Most of the instruments recorded data on photographic film which was changed by the astronauts during extra-vehicular forays, as needed.

The data captured on the film, which was brought back to earth by the astronauts, far exceeded what could have been obtained through remote sensing and telemetry with the technology of the day. Included in the main telescopes were devices for observing the Sun in a broad range of the electromagnetic spectrum, from the visual through the high energy x-ray region. Telescopes capable of forming images of the surface of the Sun in x-rays greatly increased our understanding of the dynamic character of hot regions on the solar surface, specifically explosive flares, and also the behavior of the newly discovered "coronal holes" - regions where high energy particles are escaping from the Sun at high speed. Other instruments sensitive to the ultraviolet portions of the spectrum also examined these phenomena and were capable of identifying with great accuracy the chemical and physical identity of the elements responsible. Finally, a special instrument called a coronagraph examined the visual nature of the Sun's outermost atmosphere, the Corona, and provided a three dimensional view of the nature of coronal holes. Literally every type of phenomenon known to exist on the surface and in the atmosphere of the Sun was observed in the high energy region of the spectrum inaccessible to telescopes on the surface of the Earth.


Belew, L. F. and E. Stuhlinger, Skylab, A Guidebook. GPO, 1973. NASA EP-107.

Compton, W. D. and C. D. Benson, Living and Working in Space, A History of Skylab. GPO, 1984. NASA SP-4208.

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This page updated: 08/18/99
Author: Space History Division
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