encountered on the next nighttime pass. Both Landsat-1 and -2 also 
carry & data collection system (DCS), which receives and retransmits 
data from ground sensors connected to data collection platforms 
when the satellite is in range of both a platform and a receiving 
station. 
Skylab 
The Skylab orbiting manned laboratory consisted of the Apollo command 
and service modules, a multiple-docking adapter, airlock module, 
Apollo telescope mount, and orbital workshop. The laboratory was 
launched unmanned on May 1h, 1974 (Skylab 1). The first of three 
crews to conduct data-acquisition missions (Skylab 2) was launched 
on May 22, 1973, and lasted for 31 days. Skylab 3 and 4 were 
launched on July 28 and November 16, 1973, and lasted 59 days and 
84 days, respectively. The Skylab altitude was approximately 430 km 
and the orbit inclination was 500. E 
The Skylab Earth Resources Experiment Package (EREP) sensors were a 
multispectral photographic facility (S190A), a high resolution camera 
(S190B), an infrared spectrometer (S191), a 13-channel multispectral 
scanner (S192), an X-band microwave radiometer/altimeter/scatterometer 
(S193), and an L-band microwave radiometer (S194). 
The two camera systems (S190A and B) acquired some 40,000 photographs 
of the Earth's surface. Various mixes of films and filters were used. 
The S-190A multispectral photographic facility (six 150 mm focal length, 
70-mm by 70-mm format cameras) took narrow-band black-and-white, color, 
and color-infrared photographs. The S-190B camera (460 mm focal length, 
115 x 115 mm format) took color, color-infrared, and some black-and- 
white photographs. The multispectral scanner acquired 12 bands of 
imagery between 0.41 and 2.34 um plus a thermal band at 10.2-12.5 um. 
The infrared spectrometer acquired spectrometric data in the 0.4 to 2.4 um 
and 6.2 to 15.5 um bands. The X-band radiometer/altimeter/scatterometer 
was operated in a cross-track scan or along-track scan mode, and acquired 
scatterometric, altitude, and passive microwave radiometric data at ( e 
13.8 to 14 GHz. The L-band radiometer acquired radiometric data at a 
center frequency of 1.4135 GHz. - 
Meteorological Satellites 
  
From 1972 to 1975, NASA also launched a series of experimental 
satellites containing imaging and non-imaging remote sensors. During 
the same period, NASA launched for the National Oceanographic and 
Atmospheric Agency, National Environmental Satellite Service (NOAA/NESS) 
of the U.S. Department of Commerce, operational meteorological satellites. 
The Air Force also operated the Defense Meteorological Satellite Program 
(DMSP) (Wilkes, 1975). The sensors on board the DMSP, NASA, and NOAA/NESS 
satellites are principally optical-mechanical scanners and spectrometers 
operating chiefly in the ultraviolet, visible, and infrared portions of 
the EM spectrum (Lowe, 1975; Wilkes, 1975). Although primarily intended 
to acquire imagery and other data for meteorological use, data from 
these satellites have been used successfully for small-scale geologic 
studies (Lathram, 1972; Wobber, 1972). 
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