9.4 Design Methodology
323
Fig. 9.5 Basic architecture
of TMR
9.4.8 Software Design
Onboard OBDH system had become a key part of spacecraft TT&C and application.
The OBDH system was composed of software and hardware. In the system, software
and hardware were equally important, and neither was indispensable. Hardware was
the material foundation of computer system, while the software was the soul. Recently
the processing ability requirement of onboard computer was becoming more and
more demanding, intelligent, automatic and accurate, which made the complexity
and scale of software increase dramatically. The software development was no longer
the work that the one or two people can accomplish.
Up to date, the OBDH software was usually composed of real-time operating
system and application software. Along with the continuous development of spacecraft technology and the increasing demand for practical applications, the tasks to be
handled by the computer were becoming more and more complex and the computation was becoming larger and larger. It was necessary that the computer software
should be highly portable and inheritable, and the software architecture should be
modularized and hierarchical. Software was designed according to idea of hierarchy.
In hierarchical architecture, software was organized by layers, and each layer of software was built on lower layer software. Many software systems on same layer have
same universality, and the software in the lower layer was more versatile than the
upper layer software.
The first layer of the four layers architecture was oriented to hardware, which
depended on the hardware architecture and configuration, and provided hardware
management and interface drivers. The second layer was a real-time operating system
that implements software scheduling and system calls, which could apply commercial
products. The third layer was basic service software, including monitoring, data transmission, file transmission and command processing. The fourth layer was specific
software related to specific flight missions, from simple command processing to
complex data processing. The architecture of onboard OBDH software is shown in
Fig. 9.6.
1. Real Time Multitasking Operating System
Embedded operating system is the operating system used in embedded environment.
In the embedded environment, the processor generally does not have much available
323
Fig. 9.5 Basic architecture
of TMR
9.4.8 Software Design
Onboard OBDH system had become a key part of spacecraft TT&C and application.
The OBDH system was composed of software and hardware. In the system, software
and hardware were equally important, and neither was indispensable. Hardware was
the material foundation of computer system, while the software was the soul. Recently
the processing ability requirement of onboard computer was becoming more and
more demanding, intelligent, automatic and accurate, which made the complexity
and scale of software increase dramatically. The software development was no longer
the work that the one or two people can accomplish.
Up to date, the OBDH software was usually composed of real-time operating
system and application software. Along with the continuous development of spacecraft technology and the increasing demand for practical applications, the tasks to be
handled by the computer were becoming more and more complex and the computation was becoming larger and larger. It was necessary that the computer software
should be highly portable and inheritable, and the software architecture should be
modularized and hierarchical. Software was designed according to idea of hierarchy.
In hierarchical architecture, software was organized by layers, and each layer of software was built on lower layer software. Many software systems on same layer have
same universality, and the software in the lower layer was more versatile than the
upper layer software.
The first layer of the four layers architecture was oriented to hardware, which
depended on the hardware architecture and configuration, and provided hardware
management and interface drivers. The second layer was a real-time operating system
that implements software scheduling and system calls, which could apply commercial
products. The third layer was basic service software, including monitoring, data transmission, file transmission and command processing. The fourth layer was specific
software related to specific flight missions, from simple command processing to
complex data processing. The architecture of onboard OBDH software is shown in
Fig. 9.6.
1. Real Time Multitasking Operating System
Embedded operating system is the operating system used in embedded environment.
In the embedded environment, the processor generally does not have much available