SPACE PHOTOGRAPHY 
Frederick J. Doyle 
U.S. Geological Survey 
The opening day of the XII International Congress for 
Photogrammetry in Ottawa in July 1972, was notable for the ex- 
hibition of the first photograph of the Earth acquired by a space- 
craft and an imaging system specifically designed for that purpose. 
This was the Earth Resources Technology Satellite - since renamed 
Landsat-1. It was followed into orbit in January 1975 by an 
identical Landsat 2. 
Landsat 
The characteristics of these satellites are by now well known. 
The vehicles are in a circular orbit at 915 km altitude and 97° 
inclination. Each spacecraft makes 14 revolutions per day, and 
every 18 days the entire Earth (except for the polar areas) passes 
beneath the sensors. The spacecraft are spaced 9 days apart so 
that effective coverage can be obtained at 9-day intervals. Both 
spacecraft carry a three-camera television system and a four-channel 
Multispectral Scanner (MSS). Because of power switching problems 
the TV cameras were turned off after the first few weeks of operation, 
and essentially all subsequent experiments have been conducted with 
the MSS. 
J 
The MSS images the Earth in four spectral bands: green, red, 
and two bands in the near infrared (1)*. The object scene is 
scanned by an oscillating flat mirror between the scene and a double- 
reflector telescope. .The 11.56? cross-track field of view subtends 
a swath of 185 km from the nominal 915 km altitude. The along-track 
scan is provided by the forward motion of the spacecraft. The instan- 
taneous field of view of the detectors subtends 79 m on the Earth 
surface. The detector signals are sampled, digitized, and transmitted 
to reception stations, where they are recorded on tape. The tapes 
are sent to the Goddard Space Flight Center, where they control an 
electron beam recorder which produces black-and-white images from 
each of the four bands on 70 mm film at a scale of approximately 
1:3,370,000. The four black-and-white images can be subsequently 
composited to produce color images with approximately the same 
rendition as color infrared film. Films and computer tapes are sent 
to the U.S. Geological EROS (Earth Resources Observation Systems) Data 
Center at Sioux Falls, South Dakota which serves as the distribution 
center to all users - both domestic and foreign. 
* Numbers in parentheses refer to entries in the list of references