the resolution obtained from the MSS on Landsat-1 & -2 but with the 
same coverage. The MSS on Landsat-C will have the same four spectral 
bands as on Landsat-1 & -2 with the same resolution. A fifth band 
in the thermal infrared (10.4 to 12.6 um) wavelength will have a lower 
resolution based on a 237 m pixel.  Landsat-C is scheduled to fly in 
late 1977 or early 1978. 
SKYLAB 
Skylab was launched in May 1973, and was operated during three 
occupation periods until February 1974, for a total activation of 
172 days. Its orbit at a nominal altitude of 435 km covered an 
Earth swath between 50 degrees North and South latitudes on a five- 
day cycle. Although its periods for sensor operation were limited 
by weather and astronaut schedules, sizable areas of cloud-free 
coverage were obtained. The Earth Resources Experiment Package (EREP) 
on board Skylab contained three sensors producing image data of 
significance to cartographers as follows: 
S-190A 6 camera multispectral system 
S-190B high resolution Earth Terrain Camera (ETC) 
S-192 13-channel conical scanner 
The cartographic applications of these experiments are reported in 
summary form by Colvocoresses (1975b), and Doyle (1975). 
The S-190A experiment consisted of six boresighted frame cameras of 
152.4 mm focal length (Joosten 1974). Comprehensive examination of 
this photography show it to be suited to 1:250,000 and smaller scale 
image presentations, but with a geometric quality equal to 1:50,000 
scale stereomodel standards. An evaluation of the image quality 
based on modulation transfer functions shows ground resolution 
figures for second generation photos from 60 metres to 145 metres 
depending on the film combinations used to make the copy. Acceptable 
image maps have been produced at scales of 1:250,000 to 1:100,000 and 
selected features have been revised on line maps at scales as large 
as 1:50,000. 
The S-190B experiment (McLaurin 1972), consisted of a 457 mm focal 
length frame camera with a 114.3 mm square format. With high 
resolution film, this camera provided ground resolution of 15 m. 
As reported by Vaughn (1974), relative accuracy of mapped features 
was found to be acceptable for 1:24,000 scale standards, but the 
largest scale to which the data has general cartographic application 
with acceptable accuracy is 1:50,000. 
The $-192 experiment consisted of a 13-channel conical scanner recording 
79 metre square picture elements of the Earth. An important advantage 
of this sensor is the constant aspect angle which simplifies geometric 
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