7.4 Design Methodology
239
X
Y
Z
b
Y
b
Z
150N
A04
B03
A06
B05
A03
B04
A05
B06
A01
A02
B01
B02
C05 D05
D08 C08
C01
C02
C03
C04
D06 C06
C07 D07
D01
D02
D03
D04
10N
Fig. 7.8 Thrusters configuration of Chang’E-3 the lunar lander
1. GNC Software Characteristics
(1) Embedded real-time software. All subsystem software was an embedded
system that worked together with the host computer to embed the entire
subsystem. There were number of interfaces and real-time data transmissions
within and outside the subsystem software.
The GNC subsystem was a system with high real-time requirements. The
software played a key role in command and control within the subsystem.
It undoubtedly appended high real-time requirements for software processing
and data transmissions.
(2) High reliability and high security. The lunar lander had enormous economic
value, as well as high reliability and safety requirements, and the requirements
for the GNC subsystem were even more so. As an integral part of the subsystem,
it was undoubtedly that the subsystem software should have high reliability and
security requirements.
(3) Large scale and complex architecture. Because of the high quality, high reliability, and high security requirements of the lunar lander software, the size of
the GNC subsystem software was enormous compared to similarly software.
At the same time, the architecture of the subsystem software was very complex
when it came to complicated data processing and accurate command & control
calculating.