58 
Table 12. 
Sensor 
Electronics 
Heaters 
Data Formatter 
Switch Unit 
Data Recorder 
XMT S-Band 
Antenna 
S-Band 
XMT UHF Band 
Antenna UHF 
Harness 
Thermal 
Brackets 
Balances 
Data Management 
On-Board Data Processing 
The sensor's data stream will be formatted 
and the spacecraft's time code and ephemeris 
data incorporated into the format prior to record- 
ing or transmitting data. The attitude of the 
spacecraft (pitch, roll and yaw) will be reported 
with a within-limits flag. 
The baseline data format is similar to HRPT, 
and the high-resolution data from the sensor will 
nearly fill this format at 665 kbps. The low- 
resolution data rate is one-fourth the resolution 
and one-sixteenth the data rate, or 41.6 kbps. 
The low-resolution data will be reformatted to 
transmit at 56 kbps so they can be received by 
commercially available demodulators. The high- 
and the low-resolution data for real-time trans- 
mission will be encrypted by the SeaWiFS Data 
Formatter to protect their commercial value. 
Subscribers will be furnished encryption keys. 
Weight and Power Characteristics of the SeaWiFS System 
Weight faa 
Portion of CWS 
Motor & heater 
Preliminary Estimate 
Preliminary Estimate 
Record Playback 
|e ee ee ee eee 
“a os st it fD | PO 
On-Board Data Storage 
The maximum gap in the ability to receive a 
direct downlink from the satellite at the EOSAT 
ground station amounts to about eight orbits per 
day. Since the initially planned tape-recorder ca- 
pacity would be reached after four orbits, at first 
a second ground station was premised. 
However, an alternate configuration that com- 
bines the spacecraft Support resources for the 
SeaWiFS and ETM sensors was evaluated, and 
this configuration, in conjunction with an exten- 
sion in tape-recorder capacity, obviates the need 
for a second ground station. In the alternate 
configuration, a second transport is added to 
both ETM wideband recorders, i.e., the SeaWiFS 
and the ETM use identical recording units, and 
the tape speed is altered to increase its capacity. 
Not only does this provide maximum redundancy, 
but storage capacity is provided for SeaWiFS 
data from an additional four orbits, giving a total 
storage capacity of eight orbits per day. 
