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COMPARISONS OF LANDSAT-4 WITH EARLIER LANDSATS 
Darrell M. Smith 
General Electric Company 
Lanham, Maryland 20706 
ABSTRACT 
The July 16, 1982 launch and activation of Landsat-4 was 
flawless and initial imagery from the two on-board in 
struments appear to meet or exceed expectations for radio- 
metric and geometric accuracy. The Landsat-4 program has 
been conceived as a balance between a research program 
utilizing the new Thematic Mapper (TM) and an operational 
information system that continues to provide Multispectral 
Scanner (MSS) data to an established international user 
community. Although the mission design was constrained to 
be as transparent as possible for current MSS data users, 
several modifications were necessary. Data formats remain 
essentially the same as Landsats 2 and 3, image framing and 
coverage patterns have been modified, and both radiometric 
and geometric correction accuracies have been improved. 
The TM research program will provide limited quantities of 
imagery available in the public domain until February of 
1985 when it becomes fully operational. 
LANDSAT-4 PROCESSING CONSIDERATIONS 
The Landsat-4 program represents the culmination of over 
a decade of experience by the government and General 
Electric Company in developing and operating Landsat sate 
llite systems. The realities of lessons learned from the 
Landsat 2 and 3 all-digital processing system were incor 
porated into the Landsat-4 ground segment design. High 
thruput, rapid turnaround, and high reliability were key 
design criteria in design of the MSS data processing system. 
The system is capable of supporting full production (200 
MSS scenes per day) even during single point hardware fail 
ures. Table 1 indicates some of the major features of the 
Landsat-4 program. 
Three identical, independent MSS image data processing 
lines have been developed as part of the Landsat-4 Ground 
Segment. Off-the-shelf hardware (not special purpose) and 
well-documented structured software increase system avail 
ability and decrease maintenance costs. The system is 
batch oriented as opposed to real-time or pipeline and 
therefore is more amenable to modifications should they be 
come necessary. 
Conservative design assumptions and tests to date indicate 
that the Landsat-4 ground segment will easily provide up to