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ground stations are currently configured to receive and process the 85 megabits/ 
second X-band data, though several have indicated their intention to do so. First 
will be the Canadian station at Prince Albert to provide TM coverage of the 
western United States. The separate TM processing system at GSFC will be operated 
by NASA, initially on an experimental basis producing one or two scenes/day by 
the first quarter of 1983, and full capacity of 50 scenes/day by 1985. GSFC will 
produce both film and CCT products.  EDC will receive film from GSFC and will 
supply photographic products to users, but CCTs will be supplied directly by 
GSFC. NOAA will assume operational responsibility for TM data when full capacity 
of the ground processing system has been adequately demonstrated. 
An identical spacecraft, Landsat-D prime, will be ready for launch about July 
1983. It is hoped to add wide band video tape recorders for the MSS on this 
spacecraft, but funds have not yet been provided for this modification.  Accord- 
ing to present plans, the spacecraft will not be launched until Landsat-4 begins 
to fail. Since the specification lifetime for the TM is two years and for the 
MMS is three years, this plan should provide data through 1986 to 1988. By that 
time, NOAA is expected to have reached an agreement for commercial operation of 
the Earth observation satellite systems. Both Landsat-4 and D prime are equip- 
ped for recovery and possible relaunch by the Shuttle, and a Shuttle mission has 
been designated for this purpose in 1986-7. However this may not actually be 
done because of the prospect of commercial operation using a different system 
configuration.  NOAA has proposed that they be authorized to operate the system 
if an acceptable contract cannot be reached with a commercial venture, but this 
has not been approved and no federal funding is anticipated after Landsat-D prime. 
Experimental electro-optical sensors 
  
One of the most promising imaging sensors is the linear array of charge coupled 
detectors (CCD). These arrays consist of several thousand elements and they 
can be butt-joined to provide more than 10,000 detectors per line. An optical 
system images a line from the ground scene to the line of detectors. Ground reso- 
lution in the cross-track direction depends upon detector size and the ratio of 
optical system focal length to flight altitude; in the along-track direction it 
depends on the time in which the signals can be recorded as the vehicle moves 
along the orbit. NASA has undertaken several studies of possible sensor instru- 
ments using this concept. Recently completed is the MLA (multispectral linear 
array) Instrument Definition Study. The study proposes use of the MMS launched 
by Shuttle into a Landsat-4 orbit. The sensor instrument would provide six 
spectral bands in the visible and shortwave infrared. Five of these would have 
30m IFOV and one band in the red would have 15m IFOV for recording cultural 
features. The optical system would provide +/-26° fore and aft stereo viewing 
and */-309 across track pointing for missed scene recovery. The data rate would 
be 200 megabits/second with onboard storage and data compression, and transmission 
direct to ground and via TDRSS. NASA has awarded several contracts for the design 
of an experimental demonstration instrument to be available for flight on the 
Shuttle by about 1988. 
MAPSAT 
The U.S. Geological Survey, concerned about the technical and economic viability 
of systems as complex as Landsat-4, or the NASA MLA Instrument concept, has 
completed a study for a system called MAPSAT which would provide data adequate 
for compilation of 1:50,000 scale maps with 20m contour intervals. The orbit 
would be the same as Landsat-1, -2, and -3. Three MLAs would look in the vertical 
and -/-239 fore and aft to provide stereo data. Each array would have three spec- 
tral bands and a minimum 10m IFOV, but the information could be clustered by on- 
board processing to provide lower resolution at multiples of the 10m IFOV. On- 
board data compression and selected acquisition would reduce the data rate to 
48 megabits/second which can be accommodated by minor modifications to the 
343