:
4.2.4 Redundancy
Exhibit B
used for attitude determination shall
be
Sensors and electronics redundant except for antenna feeds.
4.3 Despun Antenna Control
1
The despun system controls the rotational rate and position of the
suitable
for signal coupling and provides a communications antenna between the spinning and despun sections.
means
4.3.1 Antenna Pointing Accuracy
The east-west and north-south pointing error during the 9 year mission fuel life shall not violate the requirements of Section 3 in Beacon Tracking be at least in the earth sensor mode. The pointing accuracy 10.180 E-W and 10.21° N-S.
4.3.2 Sensors
mode shall
The despin system shall use an RF pilot signal in conjunction with the error signal, to serve as the onboard command/track receivers, which derive an control sensor.
The RF pilot signal requirements include the following:
1)
Carrier flux density incident at the spacecraft
2) Triangular waveform frequency
3) Modulation deviation
4)
Carrier frequency
-85 dBW/m2
Nominal 90-100 Hz
±1.25 MHz
6422 MHz ±200 KHz
4.3.3 Despin Acquisition Time
The specified east-west pointing accuracy shall be capable of being of control command at initial acquisition or achieved within 5 minutes subsequent reacquisition from the nominal spin rate.
4.3.4 Redundancy
The sensors, electronics, and control components shall be redundant to
The motor and resolver shall be redundant. the maximum practical extent.
4.3.5 Command Offset Pointing
a at Hong Kong and compatible The pilot station shall be located commanded E-W and N-S offset range shall be provided to meet all of the requirements of this specification at the 105.5° E and 116° E longitude orbital locations.
B-20
}