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1967 the
National Academy of Sciences (NAS) undertook such a study G3) and recommended a system com-
prised of:
305. mm focal length
230 x 460 mm format
Frame camera
150 mm focal length
70 mm format
Stellar cameras (2)
610 mm focal length
108? sweep
123 mm film width
25? convergence angle
Panoramic camera
(minimum design)
Laser altimeter 1-2 m accuracy
The validity of this approach has been amply demonstrated when a similar system was
carried around the Moon on Apollo missions 15, 16, and 17. A photogrammetric control net and
topographic maps with 15 meter internal consistency are now being produced for the Moon from
these photographs.
In the NAS study the camera systems would be mounted in an unmanned spacecraft and
exposed film would be accumulated in a capsule at the front of the vehicle. After all film had been
expended the film capsule would be ejected and recevored by aircraft. This approach was seriously
considered but failed to win final approval. The best hope for such a system now is an unmanned
package to be launched and serviced by the Shuttle.
It requires no great talent for cost-effectiveness analysis to determine that a manned
mission is a poor way to acquire photography. Too many constraints are imposed on spacecraft
dimensions, cost, power, weight, orbit, and lifetime just to keep the crew alive and assure their
return. The photographic coverage patterns achieved by Skylab in a year of operation are effective
documentation of the results obtainable from a manned mission. Hardly a single map sheet at
scales compatible with the resolution of the photography was covered with cloud-free pictures. In
terms of controlling camera operation, an electronic black box can do everything a man can do -
and more - at an infinitesimal part of the cost.
Most assuredly there is a continuing requirement for the low resolution,repetitive, sy-
noptic, multispectral data typefied by ERTS-1. But equally assured is a requirement for high re-
solution, photogrammetrically designed photography useful for standard topographic mapping. Un-
doubtedly there are severe political problems - much more stringent than the technical ones - in
acquiring high resolution data from space [1 4]. But unless these problems are faced - and solved -
the full benefit of space sensing will simply not be available to nations of the Earth. What is needed
is not an endless series of ill-conceived "'experiments'' for a number of ivory tower ‘investigations’,
but a resolve to build and operate the systems which are obviously required to produce the most
useful information. More critical than the technical problems are the organizational and adminis-
trative structures which will permit this information to be acquired and disseminated worldwide
without offending national sensitivities |l5].
References
[1] Doyle, Frederick J. - The Orthographic View from Space. International Symposium on Orthophotomapping, Paris,
France, October 1971.
[2] Earth Resources Technology Satellite Data Users Handbook, NA SA Goddard Space Flight Center, Greenbelt,
Maryland 20771.
[3] Welch, Roy - Cartographic Quality of ERTS-1 images, NASA/GSFC First ERTS Symposium, March 1973.
[4] Hooper, Ralph M. - The Mosaicking of ERTS-1 Imagery on Albers' Equal Area Projection. American Cartographer,
Vol. 1, n°1, April 1974.
[5] McEwen, Robert B. and Schoonmaker, James W. - ERTS Color Image Maps. American Society of Photogrammetry,
September 1974.
[6] Chapman, William H. - Gridding of ERTS Images. American Society of Photogrammetry, September 1974.
[7] Southard, Rupert B. and MacDonald, William R. - Cartographic and Scientific Application of ERTS-1 Ima gery in
Polar Regions. Symposium on Approaches to Earth Survey Problems through the Use of Space Techniques.
Konstanz, Federal Republic of Germany, May 1973.
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