In 1973, even as the lunar exploration phase of the Apollo program was winding down, the U.S. launched its first space station, Skylab, a large Earth-orbiting module that was actually the top or front stage of a Saturn V rocket. Visited a number of times by the astronauts, Skylab proved an excellent laboratory for many experiments including those involving systematic photography of Earth. In 1975, the last Apollo spacecraft (once destined to be on Apollo 18 to the Moon) was placed in orbit for a docking test with the (fully cooperating) Soviet Soyuz space station. It too witnessed considerable activity in photographic documentation of the Earth.

### Skylab and Apollo-Soyuz Photography

Skylab was America's first and to date only space station. It was, in a sense, a by-product of the formal Apollo program. The manned space station was a converted Saturn SIVB stage section launched dry (without fuel; and its interior fitted for habitation and operational control). It launched unmanned on the last Saturn V sent up in 1973, and astronauts arrived later. This view shows the deployed station against a black sky background, with the deployed solar panels (note that one failed to open and broke off).

The first crew, led by Pete Conrad, occupied the Skylab after rendezvous. At that time, the mission was by far the longest and most complicated of any manned flight in the U.S. space program, and was highly successful (Canby, 1974) *.

The Skylab orbit, originally planned for a 28° inclination, was increased to 50° after protests by many of the scientists involved. This higher inclination offered far more ground coverage than earlier orbits that were 32° or less. As Michael Collins has pointed out *, a 50° orbit covers 3/4ths of the Earth's surface and areas with 90% of its population. The high altitude ( 438 km; 270 miles), also increased coverage.

As shown in the pre-Apollo table **, Skylab carried an arsenal of cameras, both hard-mounted and hand-held. During three occupations of this space station, the crews acquired tens of thousands of photographs of the Earth, in addition to many astronomical pictures and other types of remote sensing images.

The view (top) of the South Island of New Zealand, showing the great Alpine fault which abruptly truncates the snow-covered Alps, and the scene below it, a larger-scale picture of Chicago taken by the S190B camera, are typical of Skylab imagery:

The very last Apollo mission was flown in 1975, involving the first link-up with a former Soviet Soyuz spacecraft (Shepard and Slayton, 1994) * . Although flown partly for political reasons, the Apollo-Soyuz Test Program (ASTP) mission generated a notable volume of useful scientific data, from on-board experiments and from photography. Experiment MA-136, under the direction of Farouk El-Baz, was more elaborate than previous 70mm photography. In particular, the astronauts selected targets more carefully for visual observation, drawing upon the Apollo lunar experiences, which had further demonstrated the value of the human eye. They also collected a substantial amount of ground and water truth-data. Because of the high latitude of the Soviet launch site, the ASTP mission had a high inclination, 51.8°,orbit that broadened the scope of regional coverage.

The astronauts took some 2,000 pictures, about 750 of these were of good quality (e.g., not cloud-obscured). Targets were diverse, covering geology, oceanography, and meteorology. A characteristic scene is this view of part of southwest Africa in Angola, where unique drainage patterns are controlled by broad, partially revegetated dune fields.

12-7: For those of you who are familiar with the major types of drainage patterns, what does the pattern in the Angola image remind you of? ANSWER

Photographs and other data from the ASTP mission were incorporated in a series of pamphlets for teachers, this being the first time educational applications were a formal objective of the Earth photography.

David Amsbury * published a general review of all pre-Shuttle Earth photography. In 1970, Kaltenbach tabulated the photographic equipment used in these missions, from Mercury through ASTP. By clicking here , you can review a series of tables from his report.

Primary Author: Nicholas M. Short, Sr. email: nmshort@ptd.net

Dr. Paul D. Lowman Jr. (lowman@denali.gsfc.nasa.gov)