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

Catalogue Introduction11 Software Architecture Design22 Implementation and Verification33 Conclusion44

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.

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.

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.

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.

Catalogue Introduction11 Software Architecture Design22 Implementation and Verification33 Conclusion44

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

2. Software Architecture Design 2.2 Software Architecture Design Based on the principles, we presented a software architecture which includes operating system layer, middleware layer and application layer.

2. Software Architecture Design 2.2 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

2. Software Architecture Design 2.2 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

2. Software Architecture Design 2.2 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

2. Software Architecture Design 2.2 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

2. Software Architecture Design 2.2 Software Architecture Design （ 2 ） Middleware Layer Application Support Layer -support SOIS MTS ， DAS ， DVS ， DDPS ， TAS ， FPSS services -support PUS services -allow Service Extension

2. Software Architecture Design 2.2 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

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 ， …

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.

Catalogue Introduction11 Software Architecture Design22 Implementation and Verification33 Conclusion44

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

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.)

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

Catalogue Introduction11 Software Architecture Design22 Implementation and Verification33 Conclusion44

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.

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.

Thank you ！