a es 86S UNM AR Y 
3 
= 
= 
Pa 
= 
D 
Zz 
LU 
7) 
Zz 
fe) 
oe 
< 
N 
o 
< 
ot) 
O 
oO 
-1.4% 
Ae = 443 NM 
Figure A-2. 
SeaWiFS esti- 
mated polariza- 
tion sensitivity. 
> —————— TOTAL SCAN ——_______ 
-20 0 
OBJECT-SPACE SCAN ANGLE, DEG 
Spacecraft and Ground Segment 
The current spacecraft configuration into 
which the SeaWiFS sensor would be integrated, 
differs from the original Landsat-6 spacecraft con- 
figuration due to programmatic changes and 
changes in the launch vehicle. The spacecraft 
concept is derived from a DMSP/TIROS-type sys- 
tem, but it has been extended to meet the EOSAT 
mission's needs. The projected SeaWiFS subsys- 
tem weight of 153 pounds is well within the 360 
pounds available for growth in the proposed 
spacecraft. Hence, the spacecraft can support 
the SeaWiFS mission and may also be able to sat- 
isfy an EOSAT goal of adding a third, spare wide- 
band recorder for the Enhanced Thematic Map- 
per (ETM) data. 
One of the key spacecraft limitations encoun- 
tered in accommodating both the SeaWiFS mission 
and ETM mission on Landsat-6 lies in the power 
subsystem. These power constraints, which will 
affect mission operations (particularly with respect 
to nighttime operations) are currently being exam- 
ined in a System Integration Study, sponsored by 
EOSAT. Some compromises in the ETM and Sea- 
WiFS tasking profiles may be necessary to accom- 
modate the SeaWiFS. However, if the required 
compromises are unacceptable, expansion of 
spacecraft power resources will be addressed. 
SeaWiFS data will be acquired for, nominally, 
40 minutes per orbit. Current plans and power 
budgets call for daylight-only imaging, but nighttime 
imagery might be acquired occasionally for experi- 
mental purposes. During imaging, SeaWiFS data 
will be transmitted in real time and recorded on 
on-board tape recorders. By combining the 
spacecraft-support resources for the SeaWiFS 
and ETM sensors and extending the capacity of 
the command/telemetry tape recorders, the eight 
orbits of data storage required for data collection 
outside the reception range of the EOSAT ground 
station can be acquired, and all stored data can 
be downlinked to a single facility. ix 
