510 
  
  
  
  
TDRS-E° OTDRS-W 
ORBITAL 
VALUE 
Normnai Altrude (km) 705.3 
Sem-maior Axis (km) i 7083.465 
inciination (deg.) | 98.22 
Penod (Mini i 38.9 
  
flocat ime) | 9:45 AM 
One Sarsiite i 16 days 
Two Sataiites i 8 days 
  
  
  
O 
DOMSAT 
  
  
  
FIGURE 2. THE SPACE ELEMENTS IN POSITION 
accuracy of the 18 satellite GPS configuration is expected to 
be within 10 meters at all times. 
TDRS-East (presently on-orbit) and TDRS-West 
(scheduled for launch in 1985) are shown in their 
geosynchronous orbits, located 41 and 171 degrees, 
respectively, West longitude and within one degree of the 
equator. In this configuration, at least one TORS will be 
within view of each Landsat for the great majority of earth 
coverage. Also shown in geosynchronous orbit is the DOMSAT 
which does not communicate with the Landsat spacecraft but 
relays Landsat data between remotely located Landsat ground 
processing facilities. 
LANDSAT EARTH COVERAGE 
The Landsat-4/5 orbit parameters differ most 
significantly from those for Landsats- 1 through 3 in 
altitude. These orbital differences result in changes in 
ground coverage patterns. Orbital parameters for Landsats -4 
and 5 were selected to achieve a repeat cycle (the period 
required to cover the entire earth surface one time) of 16 
days as opposed to 18 days for Landsat-1/2/3. The 
geographical location of individual (repeatable) ground 
tracks. are also. different for the two types of orbits. world 
Reference framing system of Path and Row identifiers had to 
be redefined for Landsat-4/5. One further ground coverage 
pattern difference relates to time between coverage of 
adjacent paths. With earlier Landsats the adjacent path to 
the West would be covered the next day. The Landsat-4/5 
orbit is such. that, given any path, the satellite wil] cover 
the adjacent path to the west seven days later. These 
swathing pattern and scene framing characteristics are 
illustrated in Figures 3 and 4.