Introduction

At the 1992 Shuttle Small Payloads Symposium, the CAN DO Project described a Gas payload called GeoCam which was designed to obtain the first ever high resolution images of the Earth taken by an educational experiment. The project team, in consultation with the National Geographic Society, had specifically designed the camera system to exactly match the optical and spectral characteristics of the NASA Skylab EREP (Earth Resource Experiment Package) camera system. The goal was to produce images that could be directly compared to the Skylab images taken two decades before. The Skylab EREP produced the first comprehensive and systematic image survey of the earth from space. These 36,000 high-resolution multispectral images represent a priceless treasure as one of the earliest possible baselines from which to evaluate the environmental changes undergone by our beleaguered planet.

Click for more information on the original GeoCam Project

The GeoCam payload (G324) did fly on STS-57 in June 1993 and produced spectacular high quality images of the Earth. The cameras were controlled by the orbiter crew based on instructions received from the first ever student operated mission control room. The GeoCam project received national attention and was the subject of a nineteen-page article in the August, 1994 National Geographic Magazine.

GeoCam has to be considered a great success. Unfortunately, not a single target was obtained that matched a Skylab EREP target area. This was a result of several factors including a 28.5^o orbital inclination as opposed to Skylab’s 50^oinclination, and a change in launch dates which put the Western Hemisphere (where most EREP targets are located) in darkness. More to the point, it clearly demonstrated that the space shuttle is not a suitable platform for highly specific targeting. The short mission duration does not allow for the required confluence of exact orbital track, sun angle, shuttle orientation, and clear weather. The International Space Station, on the other hand, is a perfect platform with an orbital inclination nearly identical to Skylab and the long timeline necessary to systematically duplicate the EREP images. The concept is as valid today as it was in 1992, but now there is a real opportunity to produce images of great educational and scientific value. The EREP images are now over a quarter of a century old, and differences will be all the more observable, and important. They can serve as a means to better understand and measure environmental degradation. The long baseline will more clearly separate long term changes from transient or short-term cyclical events. Historical examinations of change often look far back into Earth's history to determine the rate and degree of natural changes. The rapid growth of human population presents fundamentally different pressures on the Earth's ecosystem. To gain new insight on human-induced changes, earth scientists focus on the changes that have occurred over a shorter time span (25 years). During this time, natural and human induced changes on the surface of the earth have been photographed from space. Comparison between photos past and present enables documentation of profound changes to the Earth. One of the largest early data sets of earth observing photographs comes from the Skylab archives. These photographs covered much of the Earth's surface, and are an important baseline with which to compare present and future photographs. It is the major goal of the GeoCam II project to provide a direct link to this resource.

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