1. Design and Implementation of Spacecraft Avionics Software Architecture based on Spacecraft Onboard Interface Services and Packet Utilization Standard
Beijing Institute of Spacecraft System Engineering,
China Academy of Space Technology (CAST)
Xiongwen He
10/11/2015

2. Software Architecture Design Implementation and Verification
Catalogue 1
Introduction 2
Software Architecture Design 3
Implementation and Verification 4
Conclusion

3. 1. Introduction
Currently the characteristics of integration of functions have occurred in spacecraft, especially in Chinese spacecraft. Traditional spacecraft functions such as Telemetry and Telecommand, data handling and so on, have been integrated into avionics system, which also realizes the autonomous function, including information management, resource management, operation management and safety management.

4. 1. Introduction
The benefit of integration is the uniform and optimized configuration of resources, the reduction of power consumption and weight, the improvement of autonomous ability and the standardization of interface and products. However, the coupling of each subsystem is also increased and the hardware and software are becoming more complicated.
How to make the avionics system software adapt the different hardware interface, protocols and the change of user requirements, and to increase the reusability of software, is the problem that is to be solved during the avionics system software architecture design.

5. 1. Introduction
SOIS is focused on the research of onboard information exchange and the onboard interface of each subsystem and equipment. The layered architecture defined by CCSDS can shield the upper layer from the change of hardware and provide a set of standard services to be used by user applications. The concept of SOIS can be referenced and adopted in the design of avionics system software architecture.
ECSS published the Telemetry and Telecommand Packet Utilization Standard (PUS) , which defined 16 services and standardized the application layer interface between ground and spacecraft, provided support for the top-level application of avionics system.

6. 1. Introduction
With SOIS and PUS integrated, a new avionics system software architecture has been designed to solve the problem mentioned above, thus increase the software reuse, shorten the software development cycle and increase the efficiency of software development.

7. Software Architecture Design Implementation and Verification
Catalogue 1
Introduction 2
Software Architecture Design 3
Implementation and Verification 4
Conclusion

8. 2. Software Architecture Design
2.1 Principles
decompose and simplify the complex problem into several layers through layering
standardize the interface of operating system
define the framework of device drivers
establish a uniform information transfer mechanism
define the standardized components and their interfaces

9. 2. Software Architecture Design
Based on the principles, we presented a software architecture which includes operating system layer, middleware layer and application layer.

10. 2. Software Architecture Design
（1）Operating System Layer
provide a uniform API
any Operating System that supports this API can be used
include real-time kernel, BSP, device drivers and basic function library
new devices supported by add new drivers

11. 2. Software Architecture Design
（2）Middleware Layer
a common service platform
integrate SOIS and PUS
has standard program interface and protocols
is divided into three layers

12. 2. Software Architecture Design
（2）Middleware Layer
Subnetwork Layer
include onboard subnet components and space subnet components
support packet service, memory access service, synchronization service, link convergence
support TC protocol, AOS protocol
isolate the influence of the change of hardware interface and protocols

13. 2. Software Architecture Design
（2）Middleware Layer
Transfer Layer
include Space packet protocol component
space packet protocol is enhanced with address information added in the secondary header
syncretize the space link and onboard link using packets

14. 2. Software Architecture Design
（2）Middleware Layer
Application Support Layer
support SOIS MTS，DAS，DVS，DDPS，TAS，FPSS services
support PUS services
allow Service Extension

15. 2. Software Architecture Design
（3）Application Layer
contains most of the common functions of avionics system
combine the different basic services of middleware layer to implement functions
using tasks or processes with OS support

16. 2. Software Architecture Design
2.3 Interface Design
（1）Interface of each layer
Operating system layer interface: includes task management interface, interrupt management interface, memory management interface, semaphore management interface, timer management interface, IO interface, user support library interface and so on.
Subnetwork layer interface: includes packet service interface, memory access service interface, synchronization service interface, TC interface, AOS interface and so on.
Transfer Layer interface: includes space packet interface and so on.
Application Support Layer: includes PUS interface, MTS interface,DAS interface，…

17. 2. Software Architecture Design
2.3 Interface Design
（2） Interface of Component
The outside interface contains the following types.
the provided interface, including:
initialization interface
functional interface
configuration interface
the needed interface: called by this component, which is realized through configuration.

18. Software Architecture Design Implementation and Verification
Catalogue 1
Introduction 2
Software Architecture Design 3
Implementation and Verification 4
Conclusion

19. 3. Implementation and Verification
The architecture is implemented and verified based on avionics system prototype , including SMU and SDIU.
device drivers and BSP developed
28 software components of the middleware developed
coded more than lines
programmed by C language
implementation scheme for all components using method of software engineering

20. 3. Implementation and Verification
components assembled and executed on both SMU and SDIU
configuration of the software components and the operating system are pretty much the same
main differences are:
1553B convergence component :BC mode on SMU and RT mode on SDIU
Some PUS components not included in SDIU
Some configurations different (route table, device access table, device data pool configuration,etc.)

21. 3. Implementation and Verification
verified on tornado vxSim platform
result shows that the change of hardware interface and protocols can be adapted by the design of the architecture
different requirements can be realized by the combination of service components
reusability of the software is well proved
to be tested and verified on the hardware in the future

22. Software Architecture Design Implementation and Verification
Catalogue 1
Introduction 2
Software Architecture Design 3
Implementation and Verification 4
Conclusion

23. 4. Conclusion
Aiming at the trend of the function integration, synthesis and fast software development on spacecraft avionics system, the avionics system software architecture designed can adapt to the change of hardware interface, protocol and user requirements through layered design and the integration of several standard services and protocols. Thus the development of application software will be more flexible and efficient which will benefit the reuse of avionics system software so that the spacecraft life cycle will be shortened and the cost will be saved.

24. 4. Conclusion
There are still some other problems that still need to be concerned on the architecture, such as how to support the partition management of operating system, how to realize the visualized assemble of software components and the visualized simulation of information flow, etc.

25. Thank you！